Guid Structure
 

Represents a globally unique identifier (GUID).

To browse the .NET Framework source code for this type, see the Reference Source.

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

Syntax
[SerializableAttribute]
[ComVisibleAttribute(true)]
public struct Guid : IFormattable, IComparable, IComparable<Guid>, 
	IEquatable<Guid>
[SerializableAttribute]
[ComVisibleAttribute(true)]
public value struct Guid : IFormattable, IComparable, IComparable<Guid>, 
	IEquatable<Guid>
[<Sealed>]
[<SerializableAttribute>]
[<ComVisibleAttribute(true)>]
type Guid = 
    struct
        interface IFormattable
        interface IComparable
        interface IComparable<Guid>
        interface IEquatable<Guid>
    end
<SerializableAttribute>
<ComVisibleAttribute(True)>
Public Structure Guid
	Implements IFormattable, IComparable, IComparable(Of Guid), IEquatable(Of Guid)
Constructors
NameDescription
System_CAPS_pubmethod Guid

Initializes a new instance of the Guid structure by using the specified array of bytes.

System_CAPS_pubmethod Guid

Initializes a new instance of the Guid structure by using the specified integers and bytes.

System_CAPS_pubmethod Guid

Initializes a new instance of the Guid structure by using the specified integers and byte array.

System_CAPS_pubmethod Guid

Initializes a new instance of the Guid structure by using the value represented by the specified string.

System_CAPS_pubmethod Guid

Initializes a new instance of the Guid structure by using the specified unsigned integers and bytes.

Methods
NameDescription
System_CAPS_pubmethod CompareTo

Compares this instance to a specified Guid object and returns an indication of their relative values.

System_CAPS_pubmethod CompareTo

Compares this instance to a specified object and returns an indication of their relative values.

System_CAPS_pubmethod Equals

Returns a value indicating whether this instance and a specified Guid object represent the same value.

System_CAPS_pubmethod Equals

Returns a value that indicates whether this instance is equal to a specified object.(Overrides ValueTypeEquals.)

System_CAPS_pubmethod GetHashCode

Returns the hash code for this instance.(Overrides ValueTypeGetHashCode.)

System_CAPS_pubmethod GetType

Gets the Type of the current instance.(Inherited from Object.)

System_CAPS_pubmethod System_CAPS_static NewGuid

Initializes a new instance of the Guid structure.

System_CAPS_pubmethod System_CAPS_static Parse

Converts the string representation of a GUID to the equivalent Guid structure.

System_CAPS_pubmethod System_CAPS_static ParseExact

Converts the string representation of a GUID to the equivalent Guid structure, provided that the string is in the specified format.

System_CAPS_pubmethod ToByteArray

Returns a 16-element byte array that contains the value of this instance.

System_CAPS_pubmethod ToString

Returns a string representation of the value of this instance in registry format.(Overrides ValueTypeToString.)

System_CAPS_pubmethod ToString

Returns a string representation of the value of this Guid instance, according to the provided format specifier.

System_CAPS_pubmethod ToString

Returns a string representation of the value of this instance of the Guid class, according to the provided format specifier and culture-specific format information.

System_CAPS_pubmethod System_CAPS_static TryParse

Converts the string representation of a GUID to the equivalent Guid structure.

System_CAPS_pubmethod System_CAPS_static TryParseExact

Converts the string representation of a GUID to the equivalent Guid structure, provided that the string is in the specified format.

Fields
NameDescription
System_CAPS_pubfield System_CAPS_static Empty

A read-only instance of the Guid structure whose value is all zeros.

Operators
NameDescription
System_CAPS_puboperator System_CAPS_static Equality

Indicates whether the values of two specified Guid objects are equal.

System_CAPS_puboperator System_CAPS_static Inequality

Indicates whether the values of two specified Guid objects are not equal.

Remarks
System_CAPS_noteNote

To view the .NET Framework source code for this type, see the Reference Source. You can browse through the source code online, download the reference for offline viewing, and step through the sources (including patches and updates) during debugging; see instructions.

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.

Examples

The following example uses the System.Runtime.InteropServicesGuidAttribute class to assign a GUID to an interface and to a user-defined class. It retrieves the value of the GUID by calling the GetCustomAttribute method, and compares it with two other GUIDs to determine whether they are equal.

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
{
    public void MyMethod() {}

    public static void Main( string []args )
    {
        GuidAttribute IMyInterfaceAttribute = (GuidAttribute) Attribute.GetCustomAttribute(typeof(IMyInterface), typeof(GuidAttribute));

        System.Console.WriteLine("IMyInterface Attribute: " + IMyInterfaceAttribute.Value );    

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

        if (myGuid1.Equals(myGuid2))
            System.Console.WriteLine("myGuid1 equals myGuid2");
        else
            System.Console.WriteLine("myGuid1 does not equal 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" );
    }
}
// The example displays the following output:
//       IMyInterface Attribute: F9168C5E-CEB2-4faa-B6BF-329BF39FA1E4
//       myGuid1 equals myGuid2
//       myGuid1 == myGuid2
Imports System.Runtime.InteropServices

' Guid for the interface IMyInterface.
<Guid("F9168C5E-CEB2-4faa-B6BF-329BF39FA1E4")> _
Interface IMyInterface
    Sub MyMethod()
End Interface

' Guid for the coclass MyTestClass.
<Guid("936DA01F-9ABD-4d9d-80C7-02AF85C822A8")> _
Public Class MyTestClass
    Implements IMyInterface

    Public Sub MyMethod() Implements IMyInterface.MyMethod
    End Sub

    Public Shared Sub Main()
        Dim IMyInterfaceAttribute As GuidAttribute = CType(Attribute.GetCustomAttribute(GetType(IMyInterface), GetType(GuidAttribute)),
                                                           GuidAttribute)

        Console.WriteLine("IMyInterface Attribute: " + IMyInterfaceAttribute.Value)

        ' Use the string to create a guid.
        Dim myGuid1 As New Guid(IMyInterfaceAttribute.Value)
        ' Use a byte array to create a guid.
        Dim myGuid2 As New Guid(myGuid1.ToByteArray())

        If myGuid1.Equals(myGuid2) Then
            Console.WriteLine("myGuid1 equals myGuid2")
        Else
            Console.WriteLine("myGuid1 does not equal myGuid2")
        End If 

        ' The equality operator can also be used to determine if two guids have same value.
        If myGuid1.ToString() = myGuid2.ToString() Then
            Console.WriteLine("myGuid1 == myGuid2")
        Else
            Console.WriteLine("myGuid1 != myGuid2")
        End If
    End Sub
End Class
' The example displays the following output:
'       IMyInterface Attribute: F9168C5E-CEB2-4faa-B6BF-329BF39FA1E4
'       myGuid1 equals myGuid2
'       myGuid1 == myGuid2
using namespace System;
using namespace System::Runtime::InteropServices;

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


// Guid for the coclass MyTestClass.
[Guid("936DA01F-9ABD-4d9d-80C7-02AF85C822A8")]
public ref class MyTestClass: public IMyInterface
{
public:
   virtual void MyMethod(){}
};

int main()
{
   Attribute^ IMyInterfaceAttribute = Attribute::GetCustomAttribute( IMyInterface::typeid, GuidAttribute::typeid );

   // The Value property of GuidAttribute returns a string. 
   System::Console::WriteLine( String::Concat(  "IMyInterface Attribute: ", (dynamic_cast<GuidAttribute^>(IMyInterfaceAttribute))->Value ) );

   // Using the string to create a guid.
   Guid myGuid1 = Guid(dynamic_cast<GuidAttribute^>(IMyInterfaceAttribute)->Value);

   // Using a byte array to create a guid.
   Guid myGuid2 = Guid(myGuid1.ToByteArray());

   // Equals is overridden to perform a value comparison.
   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" );
}
// The example displays the following output:
//       IMyInterface Attribute: F9168C5E-CEB2-4faa-B6BF-329BF39FA1E4
//       myGuid1 equals myGuid2
//       myGuid1 == myGuid2

Note that the GuidAttribute attribute is typically used in an application to expose a type to COM. If you compile this example, you can run the Assembly Registration tool (Regasm.exe) on the generated assembly to create registry (.reg) and type library (.tlb) files. The .reg file can be used to register the coclass in the registry, and the .tlb file can provide metadata for COM interop.

Version Information
Universal Windows Platform
Available since 4.5
.NET Framework
Available since 1.1
Portable Class Library
Supported in: portable .NET platforms
Silverlight
Available since 2.0
Windows Phone Silverlight
Available since 7.0
Windows Phone
Available since 8.1
Thread Safety

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

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