Guid Structure

July 28, 2014

Represents a globally unique identifier (GUID).

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

'Declaration
Public Structure Guid _
	Implements IComparable, IComparable(Of Guid),  _
	IEquatable(Of Guid), IFormattable

The Guid type exposes the following members.

  NameDescription
Public methodGuid(Byte())Initializes a new instance of the Guid class using the specified array of bytes.
Public methodGuid(String)Initializes a new instance of the Guid class using the value represented by the specified string.
Public methodGuid(Int32, Int16, Int16, Byte())Initializes a new instance of the Guid class using the specified integers and byte array.
Public methodGuid(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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  NameDescription
Public methodCompareTo(Guid)Compares this instance to a specified Guid object and returns an indication of their relative values.
Public methodCompareTo(Object)Compares this instance to a specified object and returns an indication of their relative values.
Public methodEquals(Guid)Returns a value indicating whether this instance and a specified Guid object represent the same value.
Public methodEquals(Object)Returns a value indicating whether this instance is equal to a specified object. (Overrides ValueType.Equals(Object).)
Protected methodFinalizeAllows an object to try to free resources and perform other cleanup operations before the Object is reclaimed by garbage collection. (Inherited from Object.)
Public methodGetHashCodeReturns the hash code for this instance. (Overrides ValueType.GetHashCode.)
Public methodGetTypeGets the Type of the current instance. (Inherited from Object.)
Protected methodMemberwiseCloneCreates a shallow copy of the current Object. (Inherited from Object.)
Public methodStatic memberNewGuidInitializes a new instance of the Guid class.
Public methodStatic memberParseConverts the string representation of a GUID to the equivalent Guid value.
Public methodStatic memberParseExactConverts the string representation of a GUID to the equivalent Guid value, provided that the string is in the specified format.
Public methodToByteArrayReturns a 16-element byte array that contains the value of this instance.
Public methodToStringReturns a String representation of the value of this instance in registry format. (Overrides ValueType.ToString.)
Public methodToString(String)Returns a String representation of the value of this Guid instance, according to the provided format specifier.
Public methodToString(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.
Public methodStatic memberTryParseConverts the string representation of a GUID to the equivalent Guid value.
Public methodStatic memberTryParseExactConverts the string representation of a GUID to the equivalent Guid value, provided that the string is in the specified format.
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  NameDescription
Public operatorStatic memberEqualityIndicates whether the values of two specified Guid objects are equal.
Public operatorStatic memberInequalityReturns an indication whether the values of two specified Guid objects are not equal.
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  NameDescription
Public fieldStatic memberEmptyA read-only instance of the Guid class whose value is guaranteed to be all zeroes.
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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 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


Windows Phone OS

Supported in: 8.1, 8.0, 7.1, 7.0

Windows Phone

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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