Guid Structure

[ This article is for Windows Phone 8 developers. If you’re developing for Windows 10, see the latest documentation. ]

Represents a globally unique identifier (GUID).

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

Syntax

Public Structure Guid _
    Implements IComparable, IComparable(Of Guid),  _
    IEquatable(Of Guid), IFormattable
public struct Guid : IComparable, IComparable<Guid>, 
    IEquatable<Guid>, IFormattable

The Guid type exposes the following members.

Constructors

Name Description
Guid(array<Byte>[]()[]) Initializes a new instance of the Guid class using the specified array of bytes.
Guid(String) Initializes a new instance of the Guid class using the value represented by the specified string.
Guid(Int32, Int16, Int16, array<Byte>[]()[]) Initializes a new instance of the Guid class using the specified integers and byte array.
Guid(Int32, Int16, Int16, Byte, Byte, Byte, Byte, Byte, Byte, Byte, Byte) Initializes a new instance of the Guid class using the specified integers and bytes.

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Methods

Name Description
CompareTo(Guid) Compares this instance to a specified Guid object and returns an indication of their relative values.
CompareTo(Object) Compares this instance to a specified object and returns an indication of their relative values.
Equals(Guid) Returns a value indicating whether this instance and a specified Guid object represent the same value.
Equals(Object) Returns a value indicating whether this instance is equal to a specified object. (Overrides ValueType..::.Equals(Object).)
Finalize Allows an object to try to free resources and perform other cleanup operations before the Object is reclaimed by garbage collection. (Inherited from Object.)
GetHashCode Returns the hash code for this instance. (Overrides ValueType..::.GetHashCode()()().)
GetType Gets the Type of the current instance. (Inherited from Object.)
MemberwiseClone Creates a shallow copy of the current Object. (Inherited from Object.)
NewGuid Initializes a new instance of the Guid class.
Parse Converts the string representation of a GUID to the equivalent Guid value.
ParseExact Converts the string representation of a GUID to the equivalent Guid value, provided that the string is in the specified format.
ToByteArray Returns a 16-element byte array that contains the value of this instance.
ToString()()() Returns a String representation of the value of this instance in registry format. (Overrides ValueType..::.ToString()()().)
ToString(String) Returns a String representation of the value of this Guid instance, according to the provided format specifier.
ToString(String, IFormatProvider) 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.
TryParse Converts the string representation of a GUID to the equivalent Guid value.
TryParseExact Converts the string representation of a GUID to the equivalent Guid value, provided that the string is in the specified format.

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Operators

Name Description
Equality Indicates whether the values of two specified Guid objects are equal.
Inequality Returns an indication whether the values of two specified Guid objects are not equal.

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Fields

Name Description
Empty A read-only instance of the Guid class whose value is guaranteed to be all zeroes.

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Remarks

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 GuidAttribute class to assign a GUID to a user-defined class and an interface. It retrieves the value of the GUID by calling the Attribute..::.GetCustomAttribute method and compares it with two other GUIDs to determine whether they are equal.

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 Example
   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 Sub MyMethod() Implements IMyInterface.MyMethod
   End Sub

   Public Shared Sub Demo(ByVal outputBlock As System.Windows.Controls.TextBlock)
      ' 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.
      Dim IMyInterfaceAttribute As Attribute = Attribute.GetCustomAttribute(GetType(IMyInterface), GetType(GuidAttribute))

      ' The Value property of GuidAttribute returns a string. 
      outputBlock.Text += String.Format("IMyInterface Attribute: " + CType(IMyInterfaceAttribute, GuidAttribute).Value) & vbCrLf

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

      ' Equals is overridden and so value comparison is done though references are different.
      If myGuid1.Equals(myGuid2) Then
         outputBlock.Text &= "myGuid1 equals myGuid2" & vbCrLf
      Else
         outputBlock.Text &= "myGuid1 not equals myGuid2" & vbCrLf
      End If
      ' Equality operator can also be used to determine if two guids have same value.
      If myGuid1.ToString() = myGuid2.ToString() Then
         outputBlock.Text &= "myGuid1 == myGuid2" & vbCrLf
      Else
         outputBlock.Text &= "myGuid1 != myGuid2" & vbCrLf
      End If
      ' CompareTo returns 0 if the guids have same value.
      If myGuid1.CompareTo(myGuid2) = 0 Then
         outputBlock.Text &= "myGuid1 compares to myGuid2" & vbCrLf
      Else
         outputBlock.Text &= "myGuid1 does not compare to myGuid2" & vbCrLf
      End If

      System.Console.ReadLine()

      'Output:
      'IMyInterface Attribute: F9168C5E-CEB2-4faa-B6BF-329BF39FA1E4
      'myGuid1 equals myGuid2
      'myGuid1 == myGuid2
      'myGuid1 compares to myGuid2
   End Sub
End Class
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 Example : 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 Demo(System.Windows.Controls.TextBlock outputBlock)
   {
      // 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. 
      outputBlock.Text += "IMyInterface Attribute: " + ((GuidAttribute)IMyInterfaceAttribute).Value + "\n";

      // 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))
         outputBlock.Text += "myGuid1 equals myGuid2" + "\n";
      else
         outputBlock.Text += "myGuid1 not equals myGuid2" + "\n";

      // Equality operator can also be used to determine if two guids have same value.
      if (myGuid1 == myGuid2)
         outputBlock.Text += "myGuid1 == myGuid2" + "\n";
      else
         outputBlock.Text += "myGuid1 != myGuid2" + "\n";

      // CompareTo returns 0 if the guids have same value.
      if (myGuid1.CompareTo(myGuid2) == 0)
         outputBlock.Text += "myGuid1 compares to myGuid2" + "\n";
      else
         outputBlock.Text += "myGuid1 does not compare to myGuid2" + "\n";

      System.Console.ReadLine();

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

Version Information

Windows Phone OS

Supported in: 8.1, 8.0, 7.1, 7.0

Platforms

Windows Phone

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.

See Also

Reference

System Namespace