extends System.Enum
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| Constructors: |
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| Functions inherited from System.Enum: |
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public System.Int32 CompareTo(System.Object target) Returns the sort order of the current instance compared to the specified System.Object. Parameter target: An object to compare the current instance to. Returns: A System.Int32 containing a value that reflects the sort order of the current instance as compared to target. The following table defines the conditions under which the returned value is a negative number, zero, or a positive number. Throws: : target and the current instance are not of the same enumeration type. This method is implemented to support the System.IComparable interface. |
public System.Boolean Equals(System.Object obj) Determines whether the current instance and the specified System.Object represent the same type and value. Parameter obj: An object to compare the current instance to. Returns: true if obj is of the same enumeration type and represents the same value as the current instance; otherwise, false. This method overrides System.Object.Equals(System.Object). |
public static System.String Format(System.Type enumType, System.Object value, System.String format) Converts the specified element of the specified enumeration type to its System.String representation using the specified format. Parameter enumType: A System.Type that specifies the type of the enumeration of which value is a member. Parameter value: The enumeration element to be converted. Parameter format: A System.String that specifies the output format to use. Returns: The System.String representation of the value of the enumeration element. Throws: : enumType, value or format is a null reference. Throws: : enumType is not a System.Enum. -or- value is neither of type enumType nor does it have the same underlying type as enumType. Throws: : format contains an invalid value. For cross-platform portability, the only valid values for format are: Example: The following example demonstrates formatting enumeration values. using System;
public enum Signs {
Stop = 1,
Yield = 2,
Merge = 4
};
[Flags]
public enum Lights {
Red = 1,
Yellow = 2,
Green = 4
};
public class EnumCompTo {
public static void Main() {
Console.WriteLine(Signs.Format(typeof(Signs), Signs.Merge, "d"));
Console.WriteLine(Signs.Format(typeof(Signs), 7, "g"));
Console.WriteLine(Lights.Format(typeof(Lights), Lights.Yellow, "x"));
Console.WriteLine(Lights.Format(typeof(Lights), 7, "g"));
}
}
The output is 4 7 00000002 Red, Yellow, Green |
public System.Int32 GetHashCode() Generates a hash code for the current instance. Returns: A System.Int32 containing a hash code for the current instance. The algorithm used to generate the hash code is unspecified. This method overrides System.Object.GetHashCode. |
public static System.String GetName(System.Type enumType, System.Object value) Retrieves the name of the constant of the specified enumeration type that has the specified value. Parameter enumType: A System.Type that specifies the type of the enumeration. Parameter value: A System.Object that contains the integral value or the name of an enumeration constant. Returns: A System.String containing the name of the enumerated constant in enumType whose value is value, or a null reference if no such constant is found. Throws: : enumType or value is a null reference. Throws: : enumType is not a System.Type that describes a System.Enum . -or- value is neither of type enumType nor does it have the same underlying type as enumType. Example: The following example demonstrates the System.Enum.GetName(System.Type,System.Object) method. using System;
public enum Signs {
Stop = 1,
Yield = 2,
Merge = 4
};
public class EnumCompTo {
public static void Main() {
Console.Write( "The name of the constant with the value 4 is: " );
Console.WriteLine( "{0}.", Signs.GetName(typeof(Signs), 4));
Console.Write( "The name of the constant with the value Stop is: " );
Console.WriteLine( "{0}.", Signs.GetName(typeof(Signs), Signs.Stop ));
}
}
The output is The name of the constant with the value 4 is: Merge. The name of the constant with the value Stop is: Stop. |
public static System.String[] GetNames(System.Type enumType) Returns a zero-based, one-dimensional System.String array that contains the names of the constants of the specified enumeration type. Parameter enumType: A System.Type that specifies the type of an enumeration. Returns: A System.String vector of the names of the constants in enumType. The elements of the vector are sorted by the values of the enumerated constants. Throws: : enumType is a null reference. Throws: : enumType is not a System.Type that describes a System.Enum . Example: The following example demonstrates the System.Enum.GetNames(System.Type) method. using System;
public enum Colors {
Red,
White,
Blue
};
public class enumGetNames {
public static void Main() {
int i = 0;
String[] strAry = Colors.GetNames( typeof(Colors) );
foreach (String str in strAry) {
Console.Write("The value indexed '{0}' ", i++ );
Console.WriteLine("is {0}.", str);
}
}
}
The output is The value indexed '0' is Red. The value indexed '1' is White. The value indexed '2' is Blue. |
public static System.Type GetUnderlyingType(System.Type enumType) Returns the underlying type of the specified enumeration type. Parameter enumType: The System.Type of an enumeration. Returns: A System.Type instance that describes the underlying type of enumType. Throws: : enumType is a null reference. Throws: : enumType is not an enumeration type. Example: The following example demonstrates the System.Enum.GetUnderlyingType(System.Type) method. using System;
public enum Colors {
Red,
White,
Blue
}
public class EnumUnderlyingTypeTest {
public static void Main() {
Type t = Colors.GetUnderlyingType( typeof(Colors) );
Console.WriteLine("The underlying type of Colors is {0}.", t.ToString());
}
}
The output is The underlying type of Colors is System.Int32. |
public static System.Array GetValues(System.Type enumType) Returns a zero-based, one-dimensional array of the values of the constants of the specified enumeration type. Parameter enumType: The System.Type of an enumeration. Returns: A vector of the enumeration type specified by enumType containing the values of the constants in enumType. The elements of the array are sorted by the values of the enumeration constants. Throws: : enumType is a null reference. Throws: : enumType is not an enumeration type. Example: The following example demonstrates the System.Enum.GetValues(System.Type) method. using System;
public enum Colors {
Red = 1,
White = 2,
Blue = 4
}
public class enumGetValues {
public static void Main() {
Array valueAry = Enum.GetValues(typeof(Colors));
foreach (int i in valueAry) {
Console.WriteLine("The value of element {0} is {1}",
Enum.Format(typeof(Colors), i, "g"),i);
}
}
}
The output is The value of element Red is 1. The value of element White is 2. The value of element Blue is 4. |
public static System.Boolean IsDefined(System.Type enumType, System.Object value) Returns a System.Boolean indicating whether a constant with the specified value exists in the specified enumeration type. Parameter enumType: A System.Type that describes an enumeration. Parameter value: The constant or value being searched for in enumType. Returns: true if a constant in the enumeration described by enumType has a value equal to value; otherwise, false. Throws: : enumType or value is a null reference. Throws: : enumType is not an enumeration type. -or- The type of value is not an enumType or an underlying type of enumType. Example: The following example demonstrates the System.Enum.IsDefined(System.Type,System.Object) method. using System;
public enum Colors {
Red = 1,
White = 2,
Blue = 4
}
public class enumIsDefined {
public static void Main() {
Console.Write("It is {0} ", Enum.IsDefined(typeof(Colors), 1));
Console.WriteLine("that '1' is defined in 'Colors'.");
Console.Write("It is {0} ", Enum.IsDefined(typeof(Colors), 3));
Console.WriteLine("that '3' is defined in 'Colors'.");
}
}
The output is It is True that '1' is defined in 'Colors'. It is False that '3' is defined in 'Colors'. |
public static System.Object Parse(System.Type enumType, System.String value) Converts the specified System.String representation of one or more enumerated constants of a specified enumeration type to an equivalent enumerated object. Parameter enumType: The System.Type of an enumeration. Parameter value: A System.String containing one or more names or a single numeric value to convert. If the string contains more than one name, each name is required to be separated by a comma (','). The names are parsed in a case-sensitive manner. The names or number can be surrounded by any amount of white space. Returns: A System.Object of type enumType whose values are represented by value. Throws: : enumType or value is a null reference. Throws: : enumType is not a System.Type that describes a System.Enum. -or- value is either equal to System.String.Empty or contains only white space. -or- value represents one or more names, and at least one name represented by value is not of type enumType. This version of System.Enum.Parse(System.Type,System.String) is equivalent to System.Enum.Parse(System.Type,System.String) (enumType, value, false). Example: The following example demonstrates the System.Enum.Parse(System.Type,System.String) method. using System;
public enum Colors {
Red = 1,
Blue = 2
}
public class enumTest {
public static void Main() {
object o = Enum.Parse( typeof (Colors), "Red, Blue");
Type oType = o.GetType();
Console.WriteLine("The type of the object returned is {0}",oType.ToString());
Array values = Enum.GetValues(oType);
foreach (Colors c in values) {
Console.WriteLine(Enum.Format(oType,c,"D"));
}
}
}
The output is The type of the object returned is Colors 1 2 |
public static System.Object Parse(System.Type enumType, System.String value, System.Boolean ignoreCase) Converts the specified System.String representation of one or more enumerated constants of a specified enumeration type to an equivalent enumerated object. This method behaves in a case-sensitive or insensitive manner according to the specified System.Boolean. Parameter enumType: The System.Type of an enumeration. Parameter value: A System.String containing one or more names or a single numeric value to convert. If the string contains more than one name, each name is required to be separated by a comma (','). The names or number can be surrounded by any amount of white space. Parameter ignoreCase: A System.Boolean value. Specify true to have names in value parsed in a case-insensitive manner. Specify false to have names parsed in a case-sensitive manner. Returns: A System.Object of type enumType whose values are represented by value. Throws: : enumType or value is a null reference. Throws: : enumType is not a System.Type that describes a System.Enum. -or- value is either equal to System.String.Empty or contains only white space. -or- value represents one or more names, and at least one name represented by value is not of type enumType. Example: For an example that demonstrates parsing strings containing enumeration values, see System.Enum.Parse(System.Type,System.String)(System.Type, System.String). |
public static System.Object ToObject(System.Type enumType, System.Object value) Returns an instance of the specified enumeration type set to the specified value. Parameter enumType: The System.Type of the enumeration. Parameter value: The value to set. Returns: An enumeration object of type enumType whose value is value. Throws: : enumType is a null reference. Throws: : enumType is not a System.Type that describes a System.Enum . |
public static System.Object ToObject(System.Type enumType, System.SByte value) Returns an instance of the specified enumeration type set to the specified System.SByte value. Parameter enumType: The System.Type of an enumeration. Parameter value: The System.SByte value to set. Returns: An enumeration object of type enumType whose value is value. Throws: : enumType is a null reference. Throws: : enumType is not a System.Type that describes a System.Enum . This member is not CLS-compliant. For a CLS-compliant alternative, use System.Enum.ToObject(System.Type,System.Object)(System.Type, System.Int16). |
public static System.Object ToObject(System.Type enumType, System.Int16 value) Returns an instance of the specified enumeration type set to the specified System.Int16 value. Parameter enumType: The System.Type of an enumeration. Parameter value: The System.Int16 value to set. Returns: An enumeration object of type enumType whose value is value. Throws: : enumType is a null reference. Throws: : enumType is not a System.Type that describes a System.Enum . |
public static System.Object ToObject(System.Type enumType, System.UInt64 value) Returns an instance of the specified enumeration type set to the specified System.UInt64 value. Parameter enumType: The System.Type of an enumeration. Parameter value: The System.UInt64 value to set. Returns: An enumeration object of type enumType whose value is value. Throws: : enumType is a null reference. Throws: : enumType is not a System.Type that describes a System.Enum . This member is not CLS-compliant. For a CLS-compliant alternative, use System.Enum.ToObject(System.Type,System.Object)(System.Type, System.Int64 ). |
public static System.Object ToObject(System.Type enumType, System.Int64 value) Returns an instance of the specified enumeration type set to the specified System.Int64 value. Parameter enumType: The System.Type of an enumeration. Parameter value: The System.Int64 value to set. Returns: An enumeration object of type enumType whose value is value. Throws: : enumType is a null reference. Throws: : enumType is not a System.Type that describes a System.Enum . |
public static System.Object ToObject(System.Type enumType, System.UInt32 value) Returns an instance of the specified enumeration type set to the specified System.UInt32 value. Parameter enumType: The System.Type of an enumeration. Parameter value: The System.UInt32 value to set. Returns: An enumeration object of type enumType whose value is value. Throws: : enumType is a null reference. Throws: : enumType is not a System.Type that describes a System.Enum . This member is not CLS-compliant. For a CLS-compliant alternative, use System.Enum.ToObject(System.Type,System.Object)(System.Type, System.Int64). |
public static System.Object ToObject(System.Type enumType, System.UInt16 value) Returns an instance of the specified enumeration type set to the specified System.UInt16 value. Parameter enumType: The System.Type of an enumeration. Parameter value: The System.UInt16 value to set. Returns: An enumeration object of type enumType whose value is value. Throws: : enumType is a null reference. Throws: : enumType is not a System.Type that describes a System.Enum . This member is not CLS-compliant. For a CLS-compliant alternative, use System.Enum.ToObject(System.Type,System.Object)(System.Type, System.Int32). |
public static System.Object ToObject(System.Type enumType, System.Byte value) Returns an instance of the specified enumeration type set to the specified System.Byte value. Parameter enumType: The System.Type of an enumeration. Parameter value: The System.Byte value to set. Returns: An enumeration object of type enumType whose value is value. Throws: : enumType is a null reference. Throws: : enumType is not a System.Type that describes a System.Enum . |
public static System.Object ToObject(System.Type enumType, System.Int32 value) Returns an instance of the specified enumeration type set to the specified System.Int32 value. Parameter enumType: The System.Type of an enumeration. Parameter value: The System.Int32 value to set. Returns: An enumeration object of type enumType whose value is value. Throws: : enumType is a null reference. Throws: : enumType is not a System.Type that describes a System.Enum . |
public System.String ToString(System.String format) Converts the value of the current instance to its equivalent System.String representation using the specified format. Parameter format: A System.String that specifies the format to use when converting the current instance to a System.String. Specify one of the following values in upper or lower case: "G", "D", "X", or "F" . Returns: The System.String representation of the value of the current instance as specified by format. Throws: : format contains an invalid value. If format is a null reference or an empty string, the return value is formatted using the general format specifier ("G"). For details on the format specifiers used with an enumeration object, see System.Enum.Format(System.Type,System.Object,System.String) . |
public System.String ToString() Converts the name of the value of the current instance to its equivalent System.String representation. Returns: The System.String representation of the named constant specified by the current instance. This version of System.Enum.ToString(System.String) is equivalent to System.Enum.ToString(System.String) ("G", null ). This method returns the same value as System.Enum.Format(System.Type,System.Object,System.String) with the "g" or "G" format option. An instance of an enumeration is set to a named constant value. This method returns the name of the constant an instance is set to, not the value itself. |
public System.String ToString(System.String format, System.IFormatProvider provider) Converts the numeric value of the current instance to its equivalent System.String representation using the specified format. Parameter format: A System.String that specifies the format to use when converting the current instance to a System.String . Specify one of the following values in upper or lower case: "G", "D", "X", or "F" . Parameter provider: An object that implements the System.IFormatProvider interface or a null reference. The System.IFormatProvider is not used in the implementation of this method. There is no System.IFormatProvider that corresponds to a System.Enum object; therefore, provider is not utilized by this method, and any System.IFormatProvider may be passed as a parameter. Returns: The System.String representation of the value of the current instance as specified by format. Throws: : format does not contain a valid format specifier. If format is a null reference or an empty string, the return value is formatted using the general format specifier ("G"). For details on the format specifiers used with an enumeration object, see System.Enum.Format(System.Type,System.Object,System.String) . This method is implemented to support the System.IFormattable interface. |
public System.String ToString(System.IFormatProvider provider) Converts the name of the value of the current instance to its equivalent System.String representation. Parameter provider: An object that implements the System.IFormatProvider interface or a null reference. The System.IFormatProvider is not used in the implementation of this method. There is no System.IFormatProvider that corresponds to a System.Enum object; therefore, provider is not utilized by this method, and any System.IFormatProvider may be passed as a parameter. Returns: The System.String representation of the name of the value of the current instance. This method is equivalent to the version of System.Enum.ToString(System.String) that takes no arguments. |
| Functions inherited from System.ValueType: |
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public System.Boolean Equals(System.Object obj) Determines whether the current instance and a specified System.Object represent the same value. Parameter obj: The System.Object to compare the current instance to. Returns: true if obj and the current instance are of the same type and represent the same value; otherwise, false. This method overrides System.Object.Equals(System.Object) . |
public System.Int32 GetHashCode() Generates a hash code for the current instance. Returns: A System.Int32 containing the hash code for the current instance. The algorithm used to generate the hash code is unspecified. This method overrides System.Object.GetHashCode . |
public System.String ToString() Returns a System.String representation of the fully-qualified name of the type of the current instance. Returns: A System.String representation of the fully-qualified name of the type of the current instance. This method overrides System.Object.ToString. This method returns the System.Type.FullName property. |
| Functions inherited from System.Object: |
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public virtual System.Boolean Equals(System.Object obj) Determines whether the specified System.Object is equal to the current instance. Parameter obj: The System.Object to compare with the current instance. Returns: true if obj is equal to the current instance; otherwise, false. The statements listed below are required to be true for all implementations of the System.Object.Equals(System.Object) method. In the list, x, y, and z represent non-null object references. See System.Object.GetHashCode for additional required behaviors pertaining to the System.Object.Equals(System.Object) method. Implementations of System.Object.Equals(System.Object) should not throw exceptions. The System.Object.Equals(System.Object) method tests for referential equality , which means that System.Object.Equals(System.Object) returns true if the specified instance of Object and the current instance are the same instance; otherwise, it returns false . An implementation of the System.Object.Equals(System.Object) method is shown in the following C# code: public virtual bool Equals(Object obj) { return this == obj; } For some kinds of objects, it is desirable to have System.Object.Equals(System.Object) test for value equality instead of referential equality. Such implementations of Equals return true if the two objects have the same "value", even if they are not the same instance. The definition of what constitutes an object's "value" is up to the implementer of the type, but it is typically some or all of the data stored in the instance variables of the object. For example, the value of a System.String is based on the characters of the string; the Equals method of the System.String class returns true for any two string instances that contain exactly the same characters in the same order. When the Equals method of a base class provides value equality, an override of Equals in a class derived from that base class should invoke the inherited implementation of Equals . It is recommended (but not required) that types overriding System.Object.Equals(System.Object) also override System.Object.GetHashCode. Hashtables cannot be relied on to work correctly if this recommendation is not followed. If your programming language supports operator overloading, and if you choose to overload the equality operator for a given type, that type should override the Equals method. Such implementations of the Equals method should return the same results as the equality operator. Following this guideline will help ensure that class library code using Equals (such as System.Collections.ArrayList and System.Collections.Hashtable ) behaves in a manner that is consistent with the way the equality operator is used by application code. If you are implementing a value type, you should follow these guidelines: For reference types, the guidelines are as follows: If you implement System.IComparable on a given type, you should override Equals on that type. The System.Object.Equals(System.Object) method is called by methods in collections classes that perform search operations, including the System.Array.IndexOf(System.Array,System.Object) method and the System.Collections.ArrayList.Contains(System.Object) method. Example: Example 1: The following example contains two calls to the default implementation of System.Object.Equals(System.Object) . using System;
class MyClass {
static void Main() {
Object obj1 = new Object();
Object obj2 = new Object();
Console.WriteLine(obj1.Equals(obj2));
obj1 = obj2;
Console.WriteLine(obj1.Equals(obj2));
}
}
The output is False True Example 2: The following example shows a Point class that overrides the System.Object.Equals(System.Object) method to provide value equality and a class Point3D, which is derived from Point . Because Point's override of System.Object.Equals(System.Object) is the first in the inheritance chain to introduce value equality, the Equals method of the base class (which is inherited from System.Object and checks for referential equality) is not invoked. However, Point3D.Equals invokes Point.Equals because Point implements Equals in a manner that provides value equality. using System;
public class Point: object {
int x, y;
public override bool Equals(Object obj) {
//Check for null and compare run-time types.
if (obj == null || GetType() != obj.GetType()) return false;
Point p = (Point)obj;
return (x == p.x) && (y == p.y);
}
public override int GetHashCode() {
return x ^ y;
}
}
class Point3D: Point {
int z;
public override bool Equals(Object obj) {
return base.Equals(obj) && z == ((Point3D)obj).z;
}
public override int GetHashCode() {
return base.GetHashCode() ^ z;
}
}
The Point.Equals method checks that the obj
argument is non-null and that it references an instance of the same type as this
object. If either of those checks fail, the method returns false. The
System.Object.Equals(System.Object) method uses
System.Object.GetType to determine whether
the run-time types of the two objects are identical. (Note that
typeof is not used here because it returns the static type.) If
instead the method had used a check of the form
In Point3D.Equals , the inherited Equals method is invoked before anything else is done; the inherited Equals method checks to see that obj is non-null, that obj is an instance of the same class as this object, and that the inherited instance variables match. Only when the inherited Equals returns true does the method compare the instance variables introduced in the subclass. Specifically, the cast to Point3D is not executed unless obj has been determined to be of type Point3D or a subclass of Point3D . Example 3: In the previous example, operator == (the equality operator) is used to compare the individual instance variables. In some cases, it is appropriate to use the System.Object.Equals(System.Object) method to compare instance variables in an Equals implementation, as shown in the following example: using System;
class Rectangle {
Point a, b;
public override bool Equals(Object obj) {
if (obj == null || GetType() != obj.GetType()) return false;
Rectangle r = (Rectangle)obj;
//Use Equals to compare instance variables
return a.Equals(r.a) && b.Equals(r.b);
}
public override int GetHashCode() {
return a.GetHashCode() ^ b.GetHashCode();
}
}
Example 4: In some languages, such as C#, operator overloading is supported. When a type overloads operator ==, it should also override the System.Object.Equals(System.Object) method to provide the same functionality. This is typically accomplished by writing the Equals method in terms of the overloaded operator ==. For example: using System;
public struct Complex {
double re, im;
public override bool Equals(Object obj) {
return obj is Complex && this == (Complex)obj;
}
public override int GetHashCode() {
return re.GetHashCode() ^ im.GetHashCode();
}
public static bool operator ==(Complex x, Complex y) {
return x.re == y.re && x.im == y.im;
}
public static bool operator !=(Complex x, Complex y) {
return !(x == y);
}
}
Because Complex is a C# struct (a value type), it is known that there will be no subclasses of Complex . Therefore, the System.Object.Equals(System.Object) method need not compare the GetType() results for each object, but can instead use the is operator to check the type of the obj parameter. |
public static System.Boolean Equals(System.Object objA, System.Object objB) Determines whether two object references are equal. Parameter objA: First object to compare. Parameter objB: Second object to compare. Returns: true if one or more of the following statements is true: otherwise returns false. This static method checks for null references before it calls objA.Equals(objB ) and returns false if either objA or objB is null. If the Equals(object obj) implementation throws an exception, this method throws an exception. Example: The following example demonstrates the System.Object.Equals(System.Object) method. using System;
public class MyClass {
public static void Main() {
string s1 = "Tom";
string s2 = "Carol";
Console.WriteLine("Object.Equals(\"{0}\", \"{1}\") => {2}",
s1, s2, Object.Equals(s1, s2));
s1 = "Tom";
s2 = "Tom";
Console.WriteLine("Object.Equals(\"{0}\", \"{1}\") => {2}",
s1, s2, Object.Equals(s1, s2));
s1 = null;
s2 = "Tom";
Console.WriteLine("Object.Equals(null, \"{1}\") => {2}",
s1, s2, Object.Equals(s1, s2));
s1 = "Carol";
s2 = null;
Console.WriteLine("Object.Equals(\"{0}\", null) => {2}",
s1, s2, Object.Equals(s1, s2));
s1 = null;
s2 = null;
Console.WriteLine("Object.Equals(null, null) => {2}",
s1, s2, Object.Equals(s1, s2));
}
}
The output is Object.Equals("Tom", "Carol") => False Object.Equals("Tom", "Tom") => True Object.Equals(null, "Tom") => False Object.Equals("Carol", null) => False Object.Equals(null, null) => True |
public System.Void Finalize() Allows a System.Object to perform cleanup operations before the memory allocated for the System.Object is automatically reclaimed. During execution, System.Object.Finalize is automatically called after an object becomes inaccessible, unless the object has been exempted from finalization by a call to System.GC.SuppressFinalize(System.Object). During shutdown of an application domain, System.Object.Finalize is automatically called on objects that are not exempt from finalization, even those that are still accessible. System.Object.Finalize is automatically called only once on a given instance, unless the object is re-registered using a mechanism such as System.GC.ReRegisterForFinalize(System.Object) and System.GC.SuppressFinalize(System.Object) has not been subsequently called. Conforming implementations of the CLI are required to make every effort to ensure that for every object that has not been exempted from finalization, the System.Object.Finalize method is called after the object becomes inaccessible. However, there may be some circumstances under which Finalize is not called. Conforming CLI implementations are required to explicitly specify the conditions under which Finalize is not guaranteed to be called. For example, Finalize might not be guaranteed to be called in the event of equipment failure, power failure, or other catastrophic system failures. In addition to System.GC.ReRegisterForFinalize(System.Object) and System.GC.SuppressFinalize(System.Object), conforming implementations of the CLI are allowed to provide other mechanisms that affect the behavior of System.Object.Finalize . Any mechanisms provided are required to be specified by the CLI implementation. The order in which the Finalize methods of two objects are run is unspecified, even if one object refers to the other. The thread on which Finalize is run is unspecified. Every implementation of System.Object.Finalize in a derived type is required to call its base type's implementation of Finalize . This is the only case in which application code calls System.Object.Finalize . The System.Object.Finalize implementation does nothing. A type should implement Finalize when it uses unmanaged resources such as file handles or database connections that must be released when the managed object that uses them is reclaimed. Because Finalize methods may be invoked in any order (including from multiple threads), synchronization may be necessary if the Finalize method may interact with other objects, whether accessible or not. Furthermore, since the order in which Finalize is called is unspecified, implementers of Finalize (or of destructors implemented through overriding Finalize) must take care to correctly handle references to other objects, as their Finalize method may already have been invoked. In general, referenced objects should not be considered valid during finalization. See the System.IDisposable interface for an alternate means of disposing of resources. For C# developers: Destructors are the C# mechanism for performing cleanup operations. Destructors provide appropriate safeguards, such as automatically calling the base type's destructor. In C# code, System.Object.Finalize cannot be called or overridden. |
public virtual System.Int32 GetHashCode() Generates a hash code for the current instance. Returns: A System.Int32 containing the hash code for the current instance. System.Object.GetHashCode serves as a hash function for a specific type. A hash function is used to quickly generate a number (a hash code) corresponding to the value of an object. Hash functions are used with hashtables. A good hash function algorithm rarely generates hash codes that collide. For more information about hash functions, see The Art of Computer Programming , Vol. 3, by Donald E. Knuth. All implementations of System.Object.GetHashCode are required to ensure that for any two object references x and y, if x.Equals(y) == true, then x.GetHashCode() == y.GetHashCode(). Hash codes generated by System.Object.GetHashCode need not be unique. Implementations of System.Object.GetHashCode are not permitted to throw exceptions. The System.Object.GetHashCode implementation attempts to produce a unique hash code for every object, but the hash codes generated by this method are not guaranteed to be unique. Therefore, System.Object.GetHashCode may generate the same hash code for two different instances. It is recommended (but not required) that types overriding System.Object.GetHashCode also override System.Object.Equals(System.Object) . Hashtables cannot be relied on to work correctly if this recommendation is not followed. Use this method to obtain the hash code of an object. Hash codes should not be persisted (i.e. in a database or file) as they are allowed to change from run to run. Example: Example 1 In some cases, System.Object.GetHashCode is implemented to simply return an integer value. The following example illustrates an implementation of System.Int32.GetHashCode , which returns an integer value: using System;
public struct Int32 {
int value;
//other methods...
public override int GetHashCode() {
return value;
}
}
Example 2 Frequently, a type has multiple data members that can participate in generating the hash code. One way to generate a hash code is to combine these fields using an xor (exclusive or) operation, as shown in the following example: using System;
public struct Point {
int x;
int y;
//other methods
public override int GetHashCode() {
return x ^ y;
}
}
Example 3 The following example illustrates another case where the type's fields are combined using xor (exclusive or) to generate the hash code. Notice that in this example, the fields represent user-defined types, each of which implements System.Object.GetHashCode (and should implement System.Object.Equals(System.Object) as well): using System;
public class SomeType {
public override int GetHashCode() {
return 0;
}
}
public class AnotherType {
public override int GetHashCode() {
return 1;
}
}
public class LastType {
public override int GetHashCode() {
return 2;
}
}
public class MyClass {
SomeType a = new SomeType();
AnotherType b = new AnotherType();
LastType c = new LastType();
public override int GetHashCode () {
return a.GetHashCode() ^ b.GetHashCode() ^ c.GetHashCode();
}
}
Avoid implementing System.Object.GetHashCode in a manner that results in circular references. In other words, if AClass.GetHashCode calls BClass.GetHashCode, it should not be the case that BClass.GetHashCode calls AClass.GetHashCode. Example 4 In some cases, the data member of the class in which you are implementing System.Object.GetHashCode is bigger than a System.Int32. In such cases, you could combine the high order bits of the value with the low order bits using an XOR operation, as shown in the following example: using System;
public struct Int64 {
long value;
//other methods...
public override int GetHashCode() {
return ((int)value ^ (int)(value >> 32));
}
}
|
public System.Type GetType() Gets the type of the current instance. Returns: The instance of System.Type that represents the run-time type (the exact type) of the current instance. For two objects x and y that have identical run-time types, System.Object.ReferenceEquals(System.Object,System.Object)(x.GetType(),y.GetType()) returns true . Example: The following example demonstrates the fact that System.Object.GetType returns the run-time type of the current instance: using System;
public class MyBaseClass: Object {
}
public class MyDerivedClass: MyBaseClass {
}
public class Test {
public static void Main() {
MyBaseClass myBase = new MyBaseClass();
MyDerivedClass myDerived = new MyDerivedClass();
object o = myDerived;
MyBaseClass b = myDerived;
Console.WriteLine("mybase: Type is {0}", myBase.GetType());
Console.WriteLine("myDerived: Type is {0}", myDerived.GetType());
Console.WriteLine("object o = myDerived: Type is {0}", o.GetType());
Console.WriteLine("MyBaseClass b = myDerived: Type is {0}", b.GetType());
}
}
The output is mybase: Type is MyBaseClass myDerived: Type is MyDerivedClass object o = myDerived: Type is MyDerivedClass MyBaseClass b = myDerived: Type is MyDerivedClass |
protected System.Object MemberwiseClone() Creates a shallow copy of the current instance. Returns: A shallow copy of the current instance. The run-time type (the exact type) of the returned object is the same as the run-time type of the object that was copied. System.Object.MemberwiseClone creates a new instance of the same type as the current instance and then copies each of the object's non-static fields in a manner that depends on whether the field is a value type or a reference type. If the field is a value type, a bit-by-bit copy of all the field's bits is performed. If the field is a reference type, only the reference is copied. The algorithm for performing a shallow copy is as follows (in pseudo-code): for each instance field f in this instance if (f is a value type) bitwise copy the field if (f is a reference type) copy the reference end for loop This mechanism is referred to as a shallow copy because it copies rather than clones the non-static fields. Because System.Object.MemberwiseClone implements the above algorithm, for any object, a, the following statements are required to be true: System.Object.MemberwiseClone does not call any of the type's constructors. If System.Object.Equals(System.Object) has been overridden, a.MemberwiseClone().Equals(a) might return false . For an alternate copying mechanism, see System.ICloneable . System.Object.MemberwiseClone is protected (rather than public) to ensure that from verifiable code it is only possible to clone objects of the same class as the one performing the operation (or one of its subclasses). Although cloning an object does not directly open security holes, it does allow an object to be created without running any of its constructors. Since these constructors may establish important invariants, objects created by cloning may not have these invariants established, and this may lead to incorrect program behavior. For example, a constructor might add the new object to a linked list of all objects of this class, and cloning the object would not add the new object to that list -- thus operations that relied on the list to locate all instances would fail to notice the cloned object. By making the method protected, only objects of the same class (or a subclass) can produce a clone and implementers of those classes are (presumably) aware of the appropriate invariants and can arrange for them to be true without necessarily calling a constructor. Example: The following example shows a class called MyClass as well as a representation of the instance of MyClass returned by System.Object.MemberwiseClone . using System;
class MyBaseClass {
public static string CompanyName = "My Company";
public int age;
public string name;
}
class MyDerivedClass: MyBaseClass {
static void Main() {
//Create an instance of MyDerivedClass
//and assign values to its fields.
MyDerivedClass m1 = new MyDerivedClass();
m1.age = 42;
m1.name = "Sam";
//Do a shallow copy of m1
//and assign it to m2.
MyDerivedClass m2 = (MyDerivedClass) m1.MemberwiseClone();
}
}
A graphical representation of m1 and m2 might look like this
+---------------+
| 42 | m1
+---------------+
| +---------|-----------------> "Sam"
+---------------+ /|\
|
+---------------+ |
| 42 | | m2
+---------------+ |
| +--------|---------------------|
+---------------+
|
public static System.Boolean ReferenceEquals(System.Object objA, System.Object objB) Determines whether two object references are identical. Parameter objA: First object to compare. Parameter objB: Second object to compare. Returns: True if a and b refer to the same object or are both null references; otherwise, false. This static method provides a way to compare two objects for reference equality. It does not call any user-defined code, including overrides of System.Object.Equals(System.Object) . Example: using System;
class MyClass {
static void Main() {
object o = null;
object p = null;
object q = new Object();
Console.WriteLine(Object.ReferenceEquals(o, p));
p = q;
Console.WriteLine(Object.ReferenceEquals(p, q));
Console.WriteLine(Object.ReferenceEquals(o, p));
}
}
The output is True True False |
public virtual System.String ToString() Creates and returns a System.String representation of the current instance. Returns: A System.String representation of the current instance. System.Object.ToString returns a string whose content is intended to be understood by humans. Where the object contains culture-sensitive data, the string representation returned by System.Object.ToString takes into account the current system culture. For example, for an instance of the System.Double class whose value is zero, the implementation of System.Double.ToString might return "0.00" or "0,00" depending on the current UI culture. Although there are no exact requirements for the format of the returned string, it should as much as possible reflect the value of the object as perceived by the user. System.Object.ToString is equivalent to calling System.Object.GetType to obtain the System.Type object for the current instance and then returning the result of calling the System.Object.ToString implementation for that type. The value returned includes the full name of the type. It is recommended, but not required, that System.Object.ToString be overridden in a derived class to return values that are meaningful for that type. For example, the base data types, such as System.Int32, implement System.Object.ToString so that it returns the string form of the value the object represents. Subclasses that require more control over the formatting of strings than System.Object.ToString provides should implement System.IFormattable, whose System.Object.ToString method uses the culture of the current thread. Example: The following example outputs the textual description of the value of an object of type System.Object to the console. using System;
class MyClass {
static void Main() {
object o = new object();
Console.WriteLine (o.ToString());
}
}
The output is System.Object |
| Functions inherited from System.IComparable: |
|---|
public System.Int32 CompareTo(System.Object obj) Returns the sort order of the current instance compared to the specified object. Parameter obj: The System.Object to compare to the current instance. Returns: A System.Int32 containing a value that reflects the sort order of the current instance as compared to object. The following table defines the conditions under which the returned value is a negative number, zero, or a positive number. For any objects A, B and C, the following are required to be true: A.CompareTo(A) is required to return zero. If A.CompareTo(B) returns zero then B.CompareTo(A) is required to return zero. If A.CompareTo(B) returns zero and B.CompareTo(C) returns zero then A.CompareTo(C) is required to return zero. If A.CompareTo(B) returns a value other than zero then B.CompareTo(A) is required to return a value of the opposite sign. If A.CompareTo(B) returns a value x not equal to zero, and B.CompareTo(C) returns a value y of the same sign as x, then A.CompareTo(C) is required to a value of the same sign as x and y . The exact behavior of this method is unspecified. The intent of this method is to provide a mechanism that orders instances of a class in a manner that is consistent with the mathematical definitions of the relational operators (<, >, and ==), without regard for class-specific definitions of the operators. Use the System.IComparable.CompareTo(System.Object) method to determine the ordering of instances of a class. |
| Functions inherited from System.IFormattable: |
|---|
public System.String ToString(System.String format, System.IFormatProvider formatProvider) Returns a System.String representation of the value of the current instance. Parameter format: A System.String that specifies the format of the returned string. If format is a null reference or the empty string, the default format defined for the type of the current instance is used. Parameter formatProvider: A System.IFormatProvider that supplies a formatting object containing culture-specific formatting information, or null . Returns: A System.String containing the value of the current instance formatted in accordance with format and formatProvider . Throws: : The specified format is invalid or cannot be used with the type of the current instance. Conforming implementations do not throw an exception when format and/or formatProvider are null references. If formatProvider is a null reference, the string is constructed using a system-supplied formatting object containing information for the current system culture. If format is null, the string is constructed using a system-supplied default format appropriate for the type of the current instance. If the object returned by formatProvider supplies a culture-specific representation of symbols or patterns included in format, the returned string is required to use the information supplied by formatProvider . Implement to allow consumers of a class to use format strings and formatting objects to control the way in which the class is represented as a string. Example: The following example demonstrates using the System.IFormattable.ToString(System.String,System.IFormatProvider) method to display values in a variety of formats. The current system culture is U.S. English, which provides the default values for the formatProvider parameter of System.IFormattable.ToString(System.String,System.IFormatProvider). using System;
class FormattableExample {
public static void Main() {
double d = 123.12345678901234;
string[] formats = {"C","E","e","F","G","N","P","R"};
for (int i = 0; i< formats.Length;i++)
Console.WriteLine("{0:R} as {1}: {2}",d,formats[i],d.ToString(formats[i],null));
string[]intFormats = {"D","x","X"};
int val = 255;
for (int i = 0; i< intFormats.Length;i++)
Console.WriteLine("{0} as {1}: {2}",val,intFormats[i],val.ToString(intFormats[i],null));
}
}
The output is 123.12345678901234 as C: $123.12 123.12345678901234 as E: 1.231235E+002 123.12345678901234 as e: 1.231235e+002 123.12345678901234 as F: 123.12 123.12345678901234 as G: 123.123456789012 123.12345678901234 as N: 123.12 123.12345678901234 as P: 12,312.35 % 123.12345678901234 as R: 123.12345678901234 255 as D: 255 255 as x: ff 255 as X: FF |