System_CAPS_noteNote

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When implemented in a derived class, gets a unique identifier for this Attribute.

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

public virtual object TypeId { get; }
public:
property Object^ TypeId {
	virtual Object^ get();
}
abstract TypeId : Object with get
override TypeId : Object with get
Public Overridable ReadOnly Property TypeId As Object

Property Value

Type:

An Object that is a unique identifier for the attribute.

As implemented, this identifier is merely the Type of the attribute. However, it is intended that the unique identifier be used to identify two attributes of the same type.

The following code example implements the property in a custom parameter Attribute class and shows its use.

// Example for the Attribute.TypeId property.
using System;
using System.Reflection;

namespace NDP_UE_CS 
{
    // Define a custom parameter attribute that takes a single message argument.
    [AttributeUsage( AttributeTargets.Parameter )]
    public class ArgumentUsageAttribute : Attribute
    {
        // The constructor saves the message and creates a unique identifier.
        public ArgumentUsageAttribute( string UsageMsg )
        {
            this.usageMsg = UsageMsg;
            this.instanceGUID = Guid.NewGuid( );
        }

        // This is storage for the attribute message and unique ID.
        protected string usageMsg;
        protected Guid instanceGUID;

        // This is the Message property for the attribute.
        public string Message
        {
            get { return usageMsg; }
            set { usageMsg = value; }
        }

        // Override TypeId to provide a unique identifier for the instance.
        public override object TypeId
        {
            get { return (object)instanceGUID; }
        }

        // Override ToString() to append the message to what the base generates.
        public override string ToString( )
        {
            return base.ToString( ) + ":" + usageMsg;
        }
    }

    public class TestClass 
    {
        // Assign an ArgumentUsage attribute to each parameter.
        // Assign a ParamArray attribute to strList using the params keyword.
        public void TestMethod(
            [ArgumentUsage("Must pass an array here.")]
            String[] strArray,
            [ArgumentUsage("Can pass a param list or array here.")]
            params String[] strList)
        { }
    }

    class AttributeTypeIdDemo 
    {
        static void ShowAttributeTypeIds( ) 
        {
            // Get the class type, and then get the MethodInfo object 
            // for TestMethod to access its metadata.
            Type clsType = typeof( TestClass );
            MethodInfo mInfo = clsType.GetMethod("TestMethod");

            // There will be two elements in pInfoArray, one for each parameter.
            ParameterInfo[] pInfoArray = mInfo.GetParameters();
            if (pInfoArray != null) 
            {
                // Create an instance of the param array attribute on strList.
                ParamArrayAttribute listArrayAttr = (ParamArrayAttribute)
                    Attribute.GetCustomAttribute( pInfoArray[1], 
                        typeof(ParamArrayAttribute) );

                // Create an instance of the argument usage attribute on strArray.
                ArgumentUsageAttribute arrayUsageAttr1 = (ArgumentUsageAttribute)
                    Attribute.GetCustomAttribute( pInfoArray[0], 
                        typeof(ArgumentUsageAttribute) );

                // Create another instance of the argument usage attribute 
                // on strArray.
                ArgumentUsageAttribute arrayUsageAttr2 = (ArgumentUsageAttribute)
                    Attribute.GetCustomAttribute( pInfoArray[0], 
                        typeof(ArgumentUsageAttribute) );

                // Create an instance of the argument usage attribute on strList.
                ArgumentUsageAttribute listUsageAttr = (ArgumentUsageAttribute)
                    Attribute.GetCustomAttribute( pInfoArray[1], 
                        typeof(ArgumentUsageAttribute) );

                // Display the attributes and corresponding TypeId values.
                Console.WriteLine( "\n\"{0}\" \nTypeId: {1}",
                    listArrayAttr.ToString(), listArrayAttr.TypeId );
                Console.WriteLine( "\n\"{0}\" \nTypeId: {1}",
                    arrayUsageAttr1.ToString(), arrayUsageAttr1.TypeId );
                Console.WriteLine( "\n\"{0}\" \nTypeId: {1}",
                    arrayUsageAttr2.ToString(), arrayUsageAttr2.TypeId );
                Console.WriteLine( "\n\"{0}\" \nTypeId: {1}",
                    listUsageAttr.ToString(), listUsageAttr.TypeId );
            }
            else
                Console.WriteLine( "The parameters information could " +
                    "not be retrieved for method {0}.", mInfo.Name );
        }

        static void Main( ) 
        {
            Console.WriteLine( 
                "This example of the Attribute.TypeId property\n" +
                "generates the following output." );
            Console.WriteLine( 
                "\nCreate instances from a derived Attribute " +
                "class that implements TypeId, \nand then " +
                "display the attributes and corresponding TypeId values:" );

            ShowAttributeTypeIds( );
        }
    }
}

/*
This example of the Attribute.TypeId property
generates the following output.

Create instances from a derived Attribute class that implements TypeId,
and then display the attributes and corresponding TypeId values:

"System.ParamArrayAttribute"
TypeId: System.ParamArrayAttribute

"NDP_UE_CS.ArgumentUsageAttribute:Must pass an array here."
TypeId: d03a23f4-2536-4478-920f-8b0426dec7f1

"NDP_UE_CS.ArgumentUsageAttribute:Must pass an array here."
TypeId: a1b412e8-3047-49fa-8d03-7660d37ef718

"NDP_UE_CS.ArgumentUsageAttribute:Can pass a param list or array here."
TypeId: 7ac2bf61-0327-48d6-a07e-eb9aaf3dd45e
*/
' Example for the Attribute.TypeId property.
Imports System
Imports System.Reflection
Imports Microsoft.VisualBasic

Namespace NDP_UE_VB

    ' Define a custom parameter attribute that takes a single message argument.
    <AttributeUsage(AttributeTargets.Parameter)>  _
    Public Class ArgumentUsageAttribute
        Inherits Attribute

        ' The constructor saves the message and creates a unique identifier.
        Public Sub New(UsageMsg As String)
            Me.usageMsg = UsageMsg
            Me.GUIDinstance = Guid.NewGuid()
        End Sub ' New

        ' This is storage for the attribute message and unique ID.
        Protected usageMsg As String
        Protected GUIDinstance As Guid

        ' This is the Message property for the attribute.
        Public Property Message() As String
            Get
                Return usageMsg
            End Get
            Set
                usageMsg = value
            End Set
        End Property 

        ' Override TypeId to provide a unique identifier for the instance.
        Public Overrides ReadOnly Property TypeId() As Object
            Get
                Return CType(GUIDinstance, Object)
            End Get
        End Property

        ' Override ToString() to append the message to what base the generates.
        Public Overrides Function ToString() As String
            Return MyBase.ToString() + ":" + usageMsg
        End Function ' ToString
    End Class ' ArgumentUsageAttribute

    Public Class TestClass

        ' Assign an ArgumentUsage attribute to each parameter.
        ' Assign a ParamArray attribute to strList.
        Public Sub TestMethod( _
            <ArgumentUsage("Must pass an array here.")> _
            strArray() As String, _
            <ArgumentUsage("Can pass a param list or array here.")> _
            ParamArray strList() As String)
        End Sub ' TestMethod
    End Class ' TestClass

    Module AttributeTypeIdDemo

        ' Create attributes from the derived class, 
        ' and then display the TypeId values.
        Sub ShowAttributeTypeIds()

            ' Get the class type, and then get the MethodInfo object 
            ' for TestMethod to access its metadata.
            Dim clsType As Type = GetType(TestClass)
            Dim mInfo As MethodInfo = clsType.GetMethod("TestMethod")

            ' There will be two elements in pInfoArray, one for each parameter.
            Dim pInfoArray As ParameterInfo() = mInfo.GetParameters()
            If Not (pInfoArray Is Nothing) Then

                ' Create an instance of the param array attribute on strList.
                Dim listArrayAttr As ParamArrayAttribute = _
                    Attribute.GetCustomAttribute(pInfoArray(1), _
                        GetType(ParamArrayAttribute))

                ' Create an instance of the argument usage attribute on strArray.
                Dim arrayUsageAttr1 As ArgumentUsageAttribute = _
                    Attribute.GetCustomAttribute(pInfoArray(0), _
                        GetType(ArgumentUsageAttribute))

                ' Create another instance of the argument usage attribute 
                ' on strArray.
                Dim arrayUsageAttr2 As ArgumentUsageAttribute = _
                    Attribute.GetCustomAttribute(pInfoArray(0), _
                        GetType(ArgumentUsageAttribute))

                ' Create an instance of the argument usage attribute on strList.
                Dim listUsageAttr As ArgumentUsageAttribute = _
                    Attribute.GetCustomAttribute(pInfoArray(1), _
                        GetType(ArgumentUsageAttribute))

                ' Display the attributes and corresponding TypeId values.
                Console.WriteLine(vbCrLf & """{0}"" " & vbCrLf & "TypeId: {1}", _
                    listArrayAttr.ToString(), listArrayAttr.TypeId)
                Console.WriteLine(vbCrLf & """{0}"" " & vbCrLf & "TypeId: {1}", _
                    arrayUsageAttr1.ToString(), arrayUsageAttr1.TypeId)
                Console.WriteLine(vbCrLf & """{0}"" " & vbCrLf & "TypeId: {1}", _
                    arrayUsageAttr2.ToString(), arrayUsageAttr2.TypeId)
                Console.WriteLine(vbCrLf & """{0}"" " & vbCrLf & "TypeId: {1}", _
                    listUsageAttr.ToString(), listUsageAttr.TypeId)
            Else
                Console.WriteLine("The parameters information could not " & _
                    "be retrieved for method {0}.", mInfo.Name)
            End If
        End Sub ' ShowAttributeTypeIds

        Sub Main()
            Console.WriteLine( _
                "This example of the Attribute.TypeId property" & _
                vbCrLf & "generates the following output.")
            Console.WriteLine( _
                vbCrLf & "Create instances from a derived Attribute " & _
                "class that implements TypeId, " & vbCrLf & "and then " & _
                "display the attributes and corresponding TypeId values:" )

            ShowAttributeTypeIds( )
        End Sub ' Main

    End Module ' AttributeTypeIdDemo
End Namespace ' NDP_UE_VB

' This example of the Attribute.TypeId property
' generates the following output.
' 
' Create instances from a derived Attribute class that implements TypeId,
' and then display the attributes and corresponding TypeId values:
' 
' "System.ParamArrayAttribute"
' TypeId: System.ParamArrayAttribute
' 
' "NDP_UE_VB.ArgumentUsageAttribute:Must pass an array here."
' TypeId: f312e528-3ff9-4587-9e6d-8108b62f2980
' 
' "NDP_UE_VB.ArgumentUsageAttribute:Must pass an array here."
' TypeId: 7b2cf0ec-b166-4557-a7ab-137a57c87226
' 
' "NDP_UE_VB.ArgumentUsageAttribute:Can pass a param list or array here."
' TypeId: 0b05f2a7-4a15-4d24-99f0-8503b238a18c
// Example for the Attribute::TypeId property.
using namespace System;
using namespace System::Reflection;

namespace NDP_UE_CPP
{

   // Define a custom parameter attribute that takes a single message argument.

   [AttributeUsage(AttributeTargets::Parameter)]
   public ref class ArgumentUsageAttribute: public Attribute
   {
   protected:

      // This is storage for the attribute message and unique ID.
      String^ usageMsg;
      Guid instanceGUID;

   public:

      // The constructor saves the message and creates a unique identifier.
      ArgumentUsageAttribute( String^ UsageMsg )
      {
         this->usageMsg = UsageMsg;
         this->instanceGUID = Guid::NewGuid();
      }

      property String^ Message 
      {
         // This is the Message property for the attribute.
         String^ get()
         {
            return usageMsg;
         }

         void set( String^ value )
         {
            this->usageMsg = value;
         }
      }

      property Object^ TypeId 
      {
         // Override TypeId to provide a unique identifier for the instance.
         virtual Object^ get() override
         {
            return instanceGUID;
         }
      }

      // Override ToString() to append the message to 
      // what the base generates.
      virtual String^ ToString() override
      {
         return String::Concat( Attribute::ToString(), ":", usageMsg );
      }
   };

   public ref class TestClass
   {
   public:

      // Assign an ArgumentUsage attribute to each parameter.
      // Assign a ParamArray attribute to strList.
      void TestMethod( [ArgumentUsage("Must pass an array here.")]array<String^>^strArray,
                       [ArgumentUsage("Can pass a param list or array here.")]array<String^>^strList ){}
   };

   static void ShowAttributeTypeIds()
   {
      // Get the class type, and then get the MethodInfo object 
      // for TestMethod to access its metadata.
      Type^ clsType = TestClass::typeid;
      MethodInfo^ mInfo = clsType->GetMethod( "TestMethod" );

      // There will be two elements in pInfoArray, one for each parameter.
      array<ParameterInfo^>^pInfoArray = mInfo->GetParameters();
      if ( pInfoArray != nullptr )
      {
         // Create an instance of the param array attribute on strList.
         ParamArrayAttribute^ listArrayAttr = static_cast<ParamArrayAttribute^>(Attribute::GetCustomAttribute( pInfoArray[ 1 ], ParamArrayAttribute::typeid ));

         // Create an instance of the argument usage attribute on strArray.
         ArgumentUsageAttribute^ arrayUsageAttr1 = static_cast<ArgumentUsageAttribute^>(Attribute::GetCustomAttribute( pInfoArray[ 0 ], ArgumentUsageAttribute::typeid ));

         // Create another instance of the argument usage attribute 
         // on strArray.
         ArgumentUsageAttribute^ arrayUsageAttr2 = static_cast<ArgumentUsageAttribute^>(Attribute::GetCustomAttribute( pInfoArray[ 0 ], ArgumentUsageAttribute::typeid ));

         // Create an instance of the argument usage attribute on strList.
         ArgumentUsageAttribute^ listUsageAttr = static_cast<ArgumentUsageAttribute^>(Attribute::GetCustomAttribute( pInfoArray[ 1 ], ArgumentUsageAttribute::typeid ));

         // Display the attributes and corresponding TypeId values.
         Console::WriteLine( "\n\"{0}\" \nTypeId: {1}", listArrayAttr->ToString(), listArrayAttr->TypeId );
         Console::WriteLine( "\n\"{0}\" \nTypeId: {1}", arrayUsageAttr1->ToString(), arrayUsageAttr1->TypeId );
         Console::WriteLine( "\n\"{0}\" \nTypeId: {1}", arrayUsageAttr2->ToString(), arrayUsageAttr2->TypeId );
         Console::WriteLine( "\n\"{0}\" \nTypeId: {1}", listUsageAttr->ToString(), listUsageAttr->TypeId );
      }
      else
            Console::WriteLine( "The parameters information could "
      "not be retrieved for method {0}.", mInfo->Name );
   }
}

int main()
{
   Console::WriteLine( "This example of the Attribute::TypeId property\n"
   "generates the following output." );
   Console::WriteLine( "\nCreate instances from a derived Attribute "
   "class that implements TypeId, \nand then "
   "display the attributes and corresponding TypeId values:" );
   NDP_UE_CPP::ShowAttributeTypeIds();
}

/*
This example of the Attribute::TypeId property
generates the following output.

Create instances from a derived Attribute class that implements TypeId,
and then display the attributes and corresponding TypeId values:

"System.ParamArrayAttribute"
TypeId: System.ParamArrayAttribute

"NDP_UE_CPP.ArgumentUsageAttribute:Must pass an array here."
TypeId: 9316015d-1219-4ce1-b317-e71efb23d42e

"NDP_UE_CPP.ArgumentUsageAttribute:Must pass an array here."
TypeId: ebc1ba23-2573-4c1f-aea6-90515e733796

"NDP_UE_CPP.ArgumentUsageAttribute:Can pass a param list or array here."
TypeId: 624af10b-9bba-4403-a97e-46927e7385fb
*/
.NET Framework
Available since 1.1
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