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Guid Structure

Represents a globally unique identifier (GUID).

Namespace: System
Assembly: mscorlib (in mscorlib.dll)

[SerializableAttribute] 
[ComVisibleAttribute(true)] 
public struct Guid : IFormattable, IComparable, IComparable<Guid>, 
	IEquatable<Guid>
/** @attribute SerializableAttribute() */ 
/** @attribute ComVisibleAttribute(true) */ 
public final class Guid extends ValueType implements IFormattable, IComparable, 
	IComparable<Guid>, IEquatable<Guid>
Not applicable.

A GUID is a 128-bit integer (16 bytes) that can be used across all computers and networks wherever a unique identifier is required. Such an identifier has a very low probability of being duplicated.

The following code sample demonstrates how to attach and read a Guid object as an attribute on a user-defined class or interface.

using System;
using System.Runtime.InteropServices;

// Guid for the interface IMyInterface.
[Guid("F9168C5E-CEB2-4faa-B6BF-329BF39FA1E4")]
interface IMyInterface
{
    void MyMethod();
}

// Guid for the coclass MyTestClass.
[Guid("936DA01F-9ABD-4d9d-80C7-02AF85C822A8")]
public class MyTestClass : IMyInterface
{
    // Run regasm on this assembly to create .reg and .tlb files.
    // Reg file can be used to register this coclass in the registry.
    // Tlb file will be used to do interop.

    public void MyMethod() {}

    public static void Main( string []args )
    {
        // Example addresses the following in System.Runtime.InterOpServices.GuidAttribute.
        // How to specify the attribute on interface/coclass.
        // Retrieve the GuidAttribute from an interface/coclass.
        // Value property on GuidAttribute class.

        // Example addresses the following in System.Guid.
        // Constructor Guid(string).
        // Constructor Guid(ByteArray).
        // Equals.
        // Operator ==.
        // CompareTo.

        Attribute IMyInterfaceAttribute = Attribute.GetCustomAttribute( typeof( IMyInterface ), typeof( GuidAttribute ) );
        
        // The Value property of GuidAttribute returns a string. 
        System.Console.WriteLine( "IMyInterface Attribute: " + ((GuidAttribute)IMyInterfaceAttribute).Value );    

        // Using the string to create a guid.
        Guid myGuid1 = new Guid( ((GuidAttribute)IMyInterfaceAttribute).Value );
        // Using a byte array to create a guid.
        Guid myGuid2 = new Guid ( myGuid1.ToByteArray() );

        // Equals is overridden and so value comparison is done though references are different.
        if ( myGuid1.Equals( myGuid2 ) )
            System.Console.WriteLine( "myGuid1 equals myGuid2" );
        else
            System.Console.WriteLine( "myGuid1 not equals myGuid2" );

        // Equality operator can also be used to determine if two guids have same value.
        if ( myGuid1 == myGuid2 )
            System.Console.WriteLine( "myGuid1 == myGuid2" );
        else
            System.Console.WriteLine( "myGuid1 != myGuid2" );
    
        // CompareTo returns 0 if the guids have same value.
        if ( myGuid1.CompareTo( myGuid2 ) == 0 )
            System.Console.WriteLine( "myGuid1 compares to myGuid2" );
        else
            System.Console.WriteLine( "myGuid1 does not compare to myGuid2" );

        System.Console.ReadLine();

        //Output.
        //IMyInterface Attribute: F9168C5E-CEB2-4faa-B6BF-329BF39FA1E4
        //myGuid1 equals myGuid2
        //myGuid1 == myGuid2
        //myGuid1 compares to myGuid2
    }
}

import System.*;
import System.Runtime.InteropServices.*;

// Guid for the interface IMyInterface.
/** @attribute Guid("F9168C5E-CEB2-4faa-B6BF-329BF39FA1E4")
 */
interface IMyInterface
{
    void MyMethod();
} //IMyInterface

// Guid for the coclass MyTestClass.
/** @attribute Guid("936DA01F-9ABD-4d9d-80C7-02AF85C822A8")
 */
public class MyTestClass implements IMyInterface
{
    // Run regasm on this assembly to create .reg and .tlb files.
    // Reg file can be used to register this coclass in the registry.
    // Tlb file will be used to do interop.
    public void MyMethod()
    {
    } //MyMethod

    public static void main(String[] args)
    {
        // Example addresses the following in System.Runtime.
        // InterOpServices.GuidAttribute.
        // How to specify the attribute on interface/coclass.
        // Retrieve the GuidAttribute from an interface/coclass.
        // Value property on GuidAttribute class.
        // Example addresses the following in System.Guid.
        // Constructor Guid(string).
        // Constructor Guid(ByteArray).
        // Equals.
        // Operator ==.
        // CompareTo.
        Attribute iMyInterfaceAttribute = 
                  Attribute.GetCustomAttribute(IMyInterface.class.ToType(), 
                  GuidAttribute.class.ToType());

        // The Value property of GuidAttribute returns a string. 
        System.Console.WriteLine("IMyInterface Attribute: " 
            + ((GuidAttribute)(iMyInterfaceAttribute)).get_Value());

        // Using the string to create a guid.
        Guid myGuid1 = 
             new Guid(((GuidAttribute)(iMyInterfaceAttribute)).get_Value());
        // Using a byte array to create a guid.
        Guid myGuid2 = new Guid(myGuid1.ToByteArray());
        // Equals is overridden and so value comparison is done though 
        // references are different.
        if (myGuid1.Equals(myGuid2)) {
            System.Console.WriteLine("myGuid1 equals myGuid2");
        }
        else {
            System.Console.WriteLine("myGuid1 not equals myGuid2");
        }
        // Equality operator can also be used to determine if two 
        // guids have same value.
        if (myGuid1 == myGuid2) {
            System.Console.WriteLine("myGuid1 == myGuid2");
        }
        else {
            System.Console.WriteLine("myGuid1 != myGuid2");
        }
        // CompareTo returns 0 if the guids have same value.
        if (myGuid1.CompareTo(myGuid2) == 0) {
            System.Console.WriteLine("myGuid1 compares to myGuid2");
        }
        else {
            System.Console.WriteLine("myGuid1 does not compare to myGuid2");
        }
        System.Console.ReadLine();
    } //main 
} //MyTestClass 

//Output.
//IMyInterface Attribute: F9168C5E-CEB2-4faa-B6BF-329BF39FA1E4
//myGuid1 equals myGuid2
//myGuid1 == myGuid2
//myGuid1 compares to myGuid2

import System;
import System.Runtime.InteropServices;

// Guid for the interface IMyInterface.
Guid("F9168C5E-CEB2-4faa-B6BF-329BF39FA1E4") interface IMyInterface
{
    function MyMethod();
}

// Guid for the coclass MyTestClass.
public Guid("936DA01F-9ABD-4d9d-80C7-02AF85C822A8") class MyTestClass implements IMyInterface
{
    // Run regasm on this assembly to create .reg and .tlb files.
    // Reg file can be used to register this coclass in the registry.
    // Tlb file will be used to do interop.

    public function MyMethod() {}

    public static function Main()
    {
        // Example addresses the following in System.Runtime.InterOpServices.GuidAttribute.
        // How to specify the attribute on interface/coclass.
        // Retrieve the GuidAttribute from an interface/coclass.
        // Value property on GuidAttribute class.

        // Example addresses the following in System.Guid.
        // Constructor Guid(string).
        // Constructor Guid(ByteArray).
        // Equals.
        // Operator ==.
        // CompareTo.

        var IMyInterfaceAttribute : Attribute = Attribute.GetCustomAttribute(Type.GetType("IMyInterface"), GuidAttribute);
        
        // The Value property of GuidAttribute returns a string. 
        System.Console.WriteLine( "IMyInterface Attribute: " + (GuidAttribute(IMyInterfaceAttribute)).Value );    

        // Using the string to create a guid.
        var myGuid1 : Guid = new Guid( (GuidAttribute(IMyInterfaceAttribute)).Value );
        // Using a byte array to create a guid.
        var myGuid2 : Guid = new Guid ( myGuid1.ToByteArray() );

        // Equals is overridden and so value comparison is done though references are different.
        if ( myGuid1.Equals( myGuid2 ) )
            System.Console.WriteLine( "myGuid1 equals myGuid2" );
        else
            System.Console.WriteLine( "myGuid1 not equals myGuid2" );

        // Equality operator can also be used to determine if two guids have same value.
        if ( myGuid1 == myGuid2 )
            System.Console.WriteLine( "myGuid1 == myGuid2" );
        else
            System.Console.WriteLine( "myGuid1 != myGuid2" );
    
        // CompareTo returns 0 if the guids have same value.
        if ( myGuid1.CompareTo( myGuid2 ) == 0 )
            System.Console.WriteLine( "myGuid1 compares to myGuid2" );
        else
            System.Console.WriteLine( "myGuid1 does not compare to myGuid2" );

        System.Console.ReadLine();

        //Output.
        //IMyInterface Attribute: F9168C5E-CEB2-4faa-B6BF-329BF39FA1E4
        //myGuid1 equals myGuid2
        //myGuid1 == myGuid2
        //myGuid1 compares to myGuid2
    }
}

MyTestClass.Main();


Any public static (Shared in Visual Basic) members of this type are thread safe. Any instance members are not guaranteed to be thread safe.

Windows 98, Windows Server 2000 SP4, Windows CE, Windows Millennium Edition, Windows Mobile for Pocket PC, Windows Mobile for Smartphone, Windows Server 2003, Windows XP Media Center Edition, Windows XP Professional x64 Edition, Windows XP SP2, Windows XP Starter Edition

The Microsoft .NET Framework 3.0 is supported on Windows Vista, Microsoft Windows XP SP2, and Windows Server 2003 SP1.

.NET Framework

Supported in: 3.0, 2.0, 1.1, 1.0

.NET Compact Framework

Supported in: 2.0, 1.0

XNA Framework

Supported in: 1.0

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