public static System.String ChangeExtension(System.String path, System.String extension)

Changes the extension component of the specified path string.

Parameter path: A System.String containing the path information to modify.

Parameter extension: A System.String containing the new extension. Specify null to remove an existing extension from path.

Returns: A System.String containing the modified path information. Platforms that do not support this feature return path unmodified.

Throws: : path contains one or more implementation-defined invalid characters.

The exact behavior of this method is platform-specific. This method checks path for invalid characters as defined by the current platform and file system.

public static System.String Combine(System.String path1, System.String path2)

Concatenates two path strings.

Parameter path1: A System.String containing the first path.

Parameter path2: A System.String containing the second path.

Returns: A System.String containing path1 followed by path2. If one of the specified paths is a zero length string, this method returns the other path. If path2 contains an absolute path, this method returns path2.

Throws: : path1 or path2 is null.

Throws: : path1 or path2 contains one or more implementation-defined invalid characters.

If path1 does not end with a valid separator character (System.IO.Path.DirectorySeparatorChar or System.IO.Path.AltDirectorySeparatorChar), DirectorySeparatorChar is appended to path1 prior to the concatenation.

using System;
using System.IO;
class CombineTest {
 public static void Main() {
 string path1, path2;
 Console.WriteLine("Dir char is {0} Alt dir char is {1}",
 Path.DirectorySeparatorChar,
 Path.AltDirectorySeparatorChar
 );
 path1 = "foo.txt";
 path2 = "\\ecmatest\\examples";
 Console.WriteLine("{0} combined with {1} = {2}",path1, path2 , Path.Combine(path1, 

path2));
 path1 = "\\ecmatest\\examples";
 path2 = "foo.txt";
 Console.WriteLine("{0} combined with {1} = {2}",path1, path2 , Path.Combine(path1, 

path2));
 }
}
   

public static System.String GetDirectoryName(System.String path)

Returns the directory name component of the specified path string.

Parameter path: A System.String containing the path of a file or directory.

Returns: A System.String containing directory information for path, or null if path denotes a root directory, is the empty string, or is null. Returns System.String.Empty if path does not contain directory information.

Throws: : path contains one or more implementation-defined invalid characters.

The string returned by this method consists of all characters between the first and last System.IO.Path.DirectorySeparatorChar or System.IO.Path.AltDirectorySeparatorChar character in path. The first separator character is included, but the last separator character is not included in the returned string.

using System;
using System.IO;
class GetDirectoryTest {
 public static void Main() {
   string [] paths = {
     @"\ecmatest\examples\pathtests.txt",
     @"\ecmatest\examples\",
     "pathtests.xyzzy",
     @"\",
     @"C:\",
    @"\\myserver\myshare\foo\bar\baz.txt"
   };
   foreach (string pathString in paths) {
     string s = Path.GetDirectoryName(pathString);
     Console.WriteLine("Path: {0} directory is {1}",pathString, s== null? "null": s);
   }
 }
}

public static System.String GetExtension(System.String path)

Returns the extension component of the specified path string.

Parameter path: A System.String containing the path information from which to get the extension.

Returns: A System.String containing the extension of path, null , or System.String.Empty. If path is null, returns null. If path does not have extension information, returns System.String.Empty. The extension returned by this method includes the platform-specific extension separator character used to separate the extension from the rest of the path. Platforms that do not support this feature return path unmodified.

Throws: : path contains one or more implementation-defined invalid characters.

The exact behavior of this method is platform-specific. The character used to separate the extension from the rest of the path is platform-specific.

using System;
using System.IO;
class GetDirectoryTest {
 public static void Main(){
   string [] paths = {
     @"\ecmatest\examples\pathtests.txt",
     @"\ecmatest\examples\",
     "pathtests.xyzzy",
     "pathtests.xyzzy.txt",
     @"\",
     ""
   };
   foreach (string pathString in paths){
     string s = Path.GetExtension (pathString);
     if (s == String.Empty) s= "(empty string)";
     if (s == null) s= "null";
     Console.WriteLine("{0} is the extension of {1}", s, pathString);
   }
 }
}

public static System.String GetFileName(System.String path)

Returns the file name, including the extension if any, of the specified path string.

Parameter path: A System.String containing the path information from which to obtain the filename and extension.

Returns: A System.String consisting of the characters after the last directory character in path. If the last character of path is a directory separator character, returns System.String.Empty. If path is null, returns null. Platforms that do not support this feature return path unmodified.

Throws: : path contains one or more implementation-defined invalid characters.

The directory separator characters used to determine the start of the file name are System.IO.Path.DirectorySeparatorChar and System.IO.Path.AltDirectorySeparatorChar.

using System;
using System.IO;
class FileNameTest {
 public static void Main() {
   string [] paths = {"pathtests.txt",
     @"\ecmatest\examples\pathtests.txt",
     "c:pathtests.txt",
     @"\ecmatest\examples\",
     ""
   };
   foreach (string p in paths) {
     Console.WriteLine("Path: {0} filename = {1}",p, Path.GetFileName(p));
   }
 }
}
      

public static System.String GetFileNameWithoutExtension(System.String path)

Returns the file base component of the specified path string without the extension.

Parameter path: A System.String containing the path of the file.

Returns: A System.String consisting of the string returned by System.IO.Path.GetFileName(System.String) , minus the platform-specific extension separator character and extension. Platforms that do not support this feature return path unmodified.

Throws: : path contains one or more implementation-defined invalid characters.

For additional details, see System.IO.Path.GetFileName(System.String).

public static System.String GetFullPath(System.String path)

Returns information required to uniquely identify a file within a file system.

Parameter path: A System.String containing the file or directory for which to obtain absolute path information.

Returns: A System.String containing the fully qualified (absolute) location of path .

Throws: : path is a zero-length string, contains only white space, or contains one or more implementation-defined invalid characters. The system could not retrieve the absolute path.

Throws: : The caller does not have the required permissions.

Throws: : path is null .

Throws: : The length of path or the absolute path information for path exceeds the system-defined maximum length.

The absolute path includes all information required to locate a file or directory on a system. The file or directory specified by path is not required to exist; however if path does exist, the caller is required to have permission to obtain path information for path. Note that unlike most members of the System.IO.Path class, this method accesses the file system.

using System; 
using System.IO; 
class GetDirectoryTest { 
 public static void Main() { 
   string [] paths = { 
     @"\ecmatest\examples\pathtests.txt", 
     @"\ecmatest\examples\", 
     "pathtests.xyzzy", 
     @"\", 
   }; 
   foreach (string pathString in paths) 
     Console.WriteLine("Path: {0} full path is {1}",pathString, 

Path.GetFullPath(pathString));
 } 
}

public static System.String GetPathRoot(System.String path)

Returns the path root component of the specified path.

Parameter path: A System.String containing the path from which to obtain root directory information

Returns: A System.String containing the root directory of path, or null if path is null . Returns System.String.Empty if the specified path does not contain root information. Platforms that do not support this feature return path unmodified.

Throws: : path contains one or more implementation-defined invalid characters or is equal to System.String.Empty .

This method does not verify that the path exists. The exact behavior of this method is platform-specific.

using System;
using System.IO;
class GetPathRootTest 
{
  public static void Main() {
    string [] paths = {                                

@"\ecmatest\examples\pathtests.txt",
      "pathtests.xyzzy",
      @"\",
      @"C:\",                                  

@"\\myserver\myshare\foo\bar\baz.txt"
    };
    foreach (string pathString in paths) {
      string s = Path.GetPathRoot(pathString);
      Console.WriteLine("Path: {0} Path root is {1}",pathString, s== null? "null": s);
    }
  }
}

public static System.String GetTempFileName()

Returns a unique temporary file name and creates a 0-byte file by that name on disk.

Returns: A System.String containing the name of the temporary file. Platforms that do not support this feature return System.String.Empty.

public static System.String GetTempPath()

Returns the path information of a temporary directory.

Returns: A System.String containing the full directory name of a temporary directory. The information returned by this method is platform-specific. Platforms that do not support this feature return System.String.Empty.

Throws: : The caller does not have the required permission.

On platforms that provide a mechanism for users to discover this information, (for example by checking an environment variable), implementations of the CLI return the same information as the platform-specific mechanism.

public static System.Boolean HasExtension(System.String path)

Returns a System.Boolean indicating whether the specified path includes an extension component.

Parameter path: A System.String containing the path to search for an extension.

Returns: true if path includes a file extension. Platforms that do not support this feature return false.

Throws: : path contains one or more implementation-defined invalid characters.

public static System.Boolean IsPathRooted(System.String path)

Returns a System.Boolean indicating whether the specified path string contains a path root component.

Parameter path: A System.String containing the path to test.

Returns: true if path contains an absolute path; false if path contains relative path information. Platforms that do not support this feature return false.

Throws: : path contains one or more implementation-defined invalid characters.

This method does not access file systems or verify the existence of the specified path.

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.

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)); 
   }
}

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;
 }
}

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();
 }
}

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);
 }
}

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.

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));
   }
}
   

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.

using System;
public struct Int32 {
 int value;
 //other methods...

 public override int GetHashCode() {
 return value;
 }
}

using System;
public struct Point {
 int x;
 int y; 
 //other methods
 
 public override int GetHashCode() {
 return x ^ y;
 }
}

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();
 }
}

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 .

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());
   }
}

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.

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();
   }
}

+---------------+

|     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) .

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));
   }
}
   

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.

using System;

class MyClass {
   static void Main() {
      object o = new object();
      Console.WriteLine (o.ToString());
   }
}