闲言不叙，上官方猛料如下述：
http://msdn.microsoft.com/zh-cn/library/system.guid%28v=VS.80%29.aspx

小结：
  guid全局唯一标识符,16个字节，128位之长.

using System;
using System.Runtime.InteropServices;

// Guid for the interface IMyInterface.
 //[Guid]("GUID值") 此为接口imyinterface的guid值
 [Guid("F9168C5E-CEB2-4faa-B6BF-329BF39FA1E4")]
interface IMyInterface
{
    void MyMethod();
}

// Guid for the coclass MyTestClass.
 //同上理
 [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.
        // perator ==.
        // CompareTo.
          //attribute类对象
         //attribute zxy=attribute,getcustomattribute(typeof(类型名称),typeof(guidatrribute))
        Attribute IMyInterfaceAttribute = Attribute.GetCustomAttribute( typeof( IMyInterface ), typeof( GuidAttribute ) );
        
        // The Value property of GuidAttribute returns a string. 
         //显示接口imyinterface的guid值
          //(guidattribute)(imyinterfaceattribute).value
        System.Console.WriteLine( "IMyInterface Attribute: " + ((GuidAttribute)IMyInterfaceAttribute).Value );    

        // Using the string to create a guid.
           //基于以上接口imyinterface的guid创建一个guid对象
            guid myguid=new guid((guidattribute)imyinterfaceattribute).value)
          Guid myGuid1 = new Guid( ((GuidAttribute)IMyInterfaceAttribute).Value );
        // Using a byte array to create a guid.
        Guid myGuid2 = new Guid ( myGuid1.ToByteArray() );

           //下述不再细述，主要使用equals及==和compare,compareto相关方法比较上面
           //新建的两个guid对象的值
       // 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
    }
}