public static System.Void Delete(System.String path, System.Boolean recursive)

Deletes the specified directory and, if indicated, any subdirectories in the directory.

Parameter path: A System.String containing the name of the directory to delete. This directory must be writable and cannot contain files unless recursive is true.

Parameter recursive: Specify true to delete subdirectories and files in path; otherwise, specify false.

Throws: : path is a zero-length string, contains only white space, or contains one or more implementation-defined invalid characters.

Throws: : path is null.

Throws: : The specified path was not found.

Throws: : The directory specified by path is read-only, or recursive is false and path is not an empty directory.

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

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

The path argument is permitted to specify relative or absolute path information. Relative path information is interpreted as relative to the current working directory. To obtain the current working directory, see System.IO.Directory.GetCurrentDirectory.

public static System.Void Delete(System.String path)

Deletes the empty directory specified in path.

Parameter path: A System.String containing the name of the directory to delete. This directory must be writable and empty.

Throws: : path is a zero-length string, contains only white space, or contains one or more implementation-defined invalid characters.

Throws: : path is null.

Throws: : The specified path was not found.

Throws: : The directory specified by path is read-only or is not empty.

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

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

This method behaves identically to System.IO.Directory.Delete(System.String)(path, false ). The path argument is permitted to specify relative or absolute path information. Relative path information is interpreted as relative to the current working directory. To obtain the current working directory, see System.IO.Directory.GetCurrentDirectory.

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

Returns a System.Boolean indicating whether the specified directory exists.

Parameter path: A System.String containing the name of the directory to check.

Returns: true if the caller has the required permissions and path contains the name of an existing directory; otherwise, false. If path is null, a zero-length string, or contains the name of a file, returns false.

If the caller does not have sufficient permissions to read the files in the directory specified by path, no exception is thrown and the method returns false regardless of the existence of path. The path argument is permitted to specify relative or absolute path information. Relative path information is interpreted as relative to the current working directory. To obtain the current working directory, see System.IO.Directory.GetCurrentDirectory.

public static System.DateTime GetCreationTime(System.String path)

Returns the creation date and time of the specified file or directory.

Parameter path: A System.String containing the name of the file or directory for which to obtain creation date and time information.

Returns: A System.DateTime structure set to the creation date and time for the specified directory. This value is expressed in local time. Platforms that do not support this feature return System.DateTime.MinValue.

Throws: : path is a zero-length string, contains only white space, or contains one or more implementation-defined invalid characters.

Throws: : path is null.

Throws: : The directory specified by path was not found.

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

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

This method is equivalent to System.IO.File.GetCreationTime(System.String) (path). The path argument is permitted to specify relative or absolute path information. Relative path information is interpreted as relative to the current working directory. To obtain the current working directory, see System.IO.Directory.GetCurrentDirectory.

public static System.String GetCurrentDirectory()

Returns the application's current working directory.

Returns: A System.String containing the path of the current working directory. Platforms that do not support this feature return System.String.Empty.

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

public static System.String[] GetDirectories(System.String path)

Returns the names of subdirectories in the specified directory.

Parameter path: A System.String containing the name of the directory for which an array of subdirectory names is returned.

Returns: A System.String array containing the names of subdirectories in path.

Throws: : path is null.

Throws: : path is a zero-length string, contains only white space, or contains implementation-defined invalid characters.

Throws: : path was not found.

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

Throws: : path is a file name.

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

This method is identical to System.IO.Directory.GetDirectories(System.String) (path , "*"). The path argument is permitted to specify relative or absolute path information. Relative path information is interpreted as relative to the current working directory. To obtain the current working directory, see System.IO.Directory.GetCurrentDirectory. The names returned by this method are prefixed with the directory information provided in path.

public static System.String[] GetDirectories(System.String path, System.String searchPattern)

Returns the names of subdirectories in the specified directory that match the specified search pattern.

Parameter path: A System.String containing the starting location for the search.

Parameter searchPattern: A System.String containing the text pattern to match against the names of subdirectories of path. searchPattern cannot contain System.IO.Path.DirectorySeparatorChar or System.IO.Path.AltDirectorySeparatorChar.

Returns: A String array containing the names of subdirectories of path that match searchPattern.

Throws: : path or searchPattern is null.

Throws: : path is a zero-length string, contains only white space, or contains implementation-defined invalid characters. searchPattern does not contain a valid pattern.

Throws: : path was not found.

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

Throws: : path is a file name.

Throws: : The caller does not have permission to access the requested information.

The following wild card specifiers are permitted in searchPattern: The period (".") character, if immediately followed by a wild card specifier, indicates that the period or the empty string matches the pattern. For example, "foo.*" and "foo.?" match "foo". Note that "foo.*" and "foo*" behave identically. If the period is not immediately followed by a wildcard, it has no special meaning (it represents a period). Characters other than the wild card specifiers represent themselves, for example, the searchPattern string "*t" searches for all names inpath ending with the letter "t". The searchPattern string "s*" searches for all names in path beginning with the letter "s". The path argument is permitted to specify relative or absolute path information. Relative path information is interpreted as relative to the current working directory. To obtain the current working directory, see System.IO.Directory.GetCurrentDirectory.

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

Returns the path root component of the specified path.

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

Returns: A System.String containing the root information for the specified path. Platforms that do not support this feature return System.String.Empty.

Throws: : path is a zero-length string, contains only white space, or contains one or more implementation-defined invalid characters.

Throws: : path is null.

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

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

This method obtains the full path information for path, as returned by System.IO.Path.GetFullPath(System.String) (path) and returns the path root component. The specified path is not required to exist. The path argument is permitted to specify relative or absolute path information. Relative path information is interpreted as relative to the current working directory. To obtain the current working directory, see System.IO.Directory.GetCurrentDirectory .

using System;
using System.IO;
class GetDirectoryTest {
  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 = Directory.GetDirectoryRoot(pathString);
      Console.WriteLine("Path: {0} Directory Root is {1}",pathString, s== null? "null":s);
    }
  }
}

public static System.String[] GetFiles(System.String path, System.String searchPattern)

Returns the names of files in the specified directory that match the specified search pattern.

Parameter path: A System.String containing the name of the directory to search.

Parameter searchPattern: A System.String containing the text pattern to match against the names of files in path. searchPattern cannot contain System.IO.Path.DirectorySeparatorChar or System.IO.Path.AltDirectorySeparatorChar.

Returns: A System.String array containing the names of files in the specified directory that match the specified search pattern.

Throws: : searchPattern or path is null .

Throws: : path is a zero-length string, contains only white space, or contains one or more implementation-defined invalid characters.

Throws: : path is a file name.

Throws: : path was not found.

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

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

The following wild card specifiers are permitted in searchPattern: The period (".") character, if immediately followed by a wild card specifier, indicates that the period or the empty string matches the pattern. For example, "foo.*" and "foo.?" match "foo". Note that "foo.*" and "foo*" behave identically. If the period is not immediately followed by a wildcard, it has no special meaning (it represents a period). Characters other than the wild card specifiers and the period always represent themselves, for example, the searchPattern string "*t" searches for all names in path ending with the letter "t". The searchPattern string "s*" searches for all names in path beginning with the letter "s". The path argument is permitted to specify relative or absolute path information. Relative path information is interpreted as relative to the current working directory. To obtain the current working directory, see System.IO.Directory.GetCurrentDirectory.

public static System.String[] GetFiles(System.String path)

Returns the names of all files in the specified directory.

Parameter path: A System.String containing the name of the directory for which file names are returned.

Returns: A System.String array containing the names of the files in the specified directory. Platforms that do not support this feature return null.

Throws: : path is null.

Throws: : path is a zero-length string, contains only white space, or contains one or more implementation-defined invalid characters.

Throws: : path was not found.

Throws: : path is a file name.

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

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

This method is identical to System.IO.Directory.GetFiles(System.String) (path, "*"). The path argument is permitted to specify relative or absolute path information. Relative path information is interpreted as relative to the current working directory. To obtain the current working directory, see System.IO.Directory.GetCurrentDirectory.

public static System.String[] GetFileSystemEntries(System.String path)

Returns the names of all files and subdirectories in the specified directory.

Parameter path: A System.String containing the name of the directory for which file and subdirectory names are returned.

Returns: A System.String array containing the names of file system entries in the specified directory.

Throws: : path is null .

Throws: : path is a zero-length string, contains only white space, or contains one or more implementation-defined invalid characters.

Throws: : path was not found.

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

Throws: : path is a file name.

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

This method is identical to System.IO.Directory.GetFileSystemEntries(System.String) (path, "*"). The names returned by this method are prefixed with the directory information provided in path. The path argument is permitted to specify relative or absolute path information. Relative path information is interpreted as relative to the current working directory. To obtain the current working directory, see System.IO.Directory.GetCurrentDirectory .

public static System.String[] GetFileSystemEntries(System.String path, System.String searchPattern)

Returns an array of file and directory names matching the specified search criteria.

Parameter path: A System.String containing the name of the directory to search.

Parameter searchPattern: A System.String containing the text pattern for which to search. searchPattern cannot contain System.IO.Path.DirectorySeparatorChar or System.IO.Path.AltDirectorySeparatorChar .

Returns: A String array containing file and directory names matching the specified search criteria.

Throws: : searchPattern or path is null.

Throws: : path is a zero-length string, contains only white space, or contains one or more implementation-defined invalid characters.

Throws: : path was not found.

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

Throws: : path is a file name.

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

The following wild card specifiers are permitted in searchPattern: The period (".") character, if immediately followed by a wild card specifier, indicates that the period or the empty string matches the pattern. For example, "foo.*" and "foo.?" match "foo". Note that "foo.*" and "foo*" behave identically. If the period is not immediately followed by a wildcard, it has no special meaning (it represents a period). Characters other than the wild card specifiers represent themselves, for example, the searchPattern string "*t" searches for all names in path ending with the letter "t". The searchPattern string "s*" searches for all names in path beginning with the letter "s". The names returned by this method are prefixed with the directory information provided in path. The path argument is permitted to specify relative or absolute path information. Relative path information is interpreted as relative to the current working directory. To obtain the current working directory, see System.IO.Directory.GetCurrentDirectory.

public static System.DateTime GetLastAccessTime(System.String path)

Returns the date and time the specified file or directory was last accessed.

Parameter path: A System.String containing the name of the file or directory for which to obtain access date and time information.

Returns: A System.DateTime structure set to the date and time the specified file or directory was last accessed. This value is expressed in local time. Platforms that do not support this feature return System.DateTime.MinValue.

Throws: : path is a zero-length string, contains only white space, or contains one or more implementation-defined invalid characters.

Throws: : path is null.

Throws: : The specified path was not found.

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

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

This method is equivalent to System.IO.File.GetLastAccessTime(System.String) (path). The path argument is permitted to specify relative or absolute path information. Relative path information is interpreted as relative to the current working directory. To obtain the current working directory, see System.IO.Directory.GetCurrentDirectory.

public static System.DateTime GetLastWriteTime(System.String path)

Returns the date and time the specified file or directory was last written to.

Parameter path: A System.String containing the name of the file or directory for which to obtain modification date and time information.

Returns: A System.DateTime structure set to the date and time the specified file or directory was last written to. This value is expressed in local time. Platforms that do not support this feature return System.DateTime.MinValue.

Throws: : path is a zero-length string, contains only white space, or contains one or more implementation-defined invalid characters.

Throws: : path is null.

Throws: : The specified path was not found.

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

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

This method is equivalent to System.IO.File.GetLastWriteTime(System.String) (path ). The path argument is permitted to specify relative or absolute path information. Relative path information is interpreted as relative to the current working directory. To obtain the current working directory, see System.IO.Directory.GetCurrentDirectory.

public static System.Void Move(System.String sourceDirName, System.String destDirName)

Moves a file or a directory and its contents to a new location.

Parameter sourceDirName: A System.String containing the name of the file or directory to move.

Parameter destDirName: A System.String containing the new location for sourceDirName. This string cannot identify an existing file or directory.

Throws: : sourceDirName or destDirName is a zero-length string, contains only white space, or contains implementation-defined invalid characters.

Throws: : sourceDirName or destDirName is null.

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

Throws: : An attempt was made to move a directory to a different volume, or destDirName already exists.

Throws: : sourceDirName was not found.

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

The destDirName argument cannot specify a location on a different disk or volume than sourceDirName. The sourceDirName and destDirName arguments cannot identify the same file or directory. This method throws a System.IO.IOException if, for example, you try to move "\mydir" to "\public", and "\public" already exists. You must specify "\public\mydir" as the destDirName. The sourceDirName and destDirName arguments are permitted to specify relative or absolute path information. Relative path information is interpreted as relative to the current working directory. To obtain the current working directory, see System.IO.Directory.GetCurrentDirectory.

public static System.Void SetCreationTime(System.String path, System.DateTime creationTime)

Sets the creation date and time for the specified file or directory.

Parameter path: A System.String containing the name of the file or directory for which to set the creation date and time information.

Parameter creationTime: A System.DateTime containing the value to set for the creation date and time of path. This value is expressed in local time.

Throws: : path is a zero-length string, contains only white space, or contains one or more implementation-defined invalid characters.

Throws: : creationTime specifies a value outside the range of date/times permitted for this operation.

Throws: : path is null.

Throws: : path was not found.

Throws: : An I/O error occurred while performing the operation.

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

The path argument is permitted to specify relative or absolute path information. Relative path information is interpreted as relative to the current working directory. To obtain the current working directory, see System.IO.Directory.GetCurrentDirectory. On platforms that do not support this feature, this method has no effect. If this feature is supported, the range of dates that is valid for this operation is implementation-specific.

public static System.Void SetCurrentDirectory(System.String path)

Sets the application's current working directory to the specified directory.

Parameter path: A System.String containing the path to which the current working directory is set.

Throws: : path is a zero-length string, contains only white space, or contains one or more implementation-defined invalid characters.

Throws: : path is null.

Throws: : path was not found.

Throws: : An I/O error occurred while performing the operation.

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

When the application terminates, the working directory is restored to its original location (the directory where the process was started). The path argument is permitted to specify relative or absolute path information. Relative path information is interpreted as relative to the current working directory. To obtain the current working directory, see System.IO.Directory.GetCurrentDirectory. On platforms that do not support this feature, this method has no effect.

public static System.Void SetLastAccessTime(System.String path, System.DateTime lastAccessTime)

Sets the date and time the specified file or directory was last accessed.

Parameter path: A System.String containing the name of the file or directory for which to set the access date and time information.

Parameter lastAccessTime: A System.DateTime containing the value to set for the access date and time of path. This value is expressed in local time.

Throws: : path is a zero-length string, contains only white space, or contains one or more implementation-defined invalid characters.

Throws: : path is null.

Throws: : path was not found.

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

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

The path argument is permitted to specify relative or absolute path information. Relative path information is interpreted as relative to the current working directory. To obtain the current working directory, see System.IO.Directory.GetCurrentDirectory. On platforms that do not support this feature, this method has no effect. If this feature is supported, the range of dates that is valid for this operation is implementation-specific.

public static System.Void SetLastWriteTime(System.String path, System.DateTime lastWriteTime)

Sets the date and time a directory was last written to.

Parameter path: A System.String containing the name of the directory for which to set the date and time information.

Parameter lastWriteTime: A System.DateTime containing the value to set for the last write date and time of path. This value is expressed in local time.

Throws: : path is a zero-length string, contains only white space, or contains one or more implementation-defined invalid characters.

Throws: : path is null.

Throws: : path was not found.

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

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

Relative path information is interpreted as relative to the current working directory. To obtain the current working directory, see System.IO.Directory.GetCurrentDirectory. On platforms that do not support this feature, this method has no effect. If this feature is supported, the range of dates that is valid for this operation is implementation-specific.

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());
   }
}