Attribute.TypeId Proprietà

public:
 virtual property System::Object ^ TypeId { System::Object ^ get(); };

public virtual object TypeId { get; }

member this.TypeId : obj

Public Overridable ReadOnly Property TypeId As Object

Valore della proprietà

Oggetto Object che rappresenta un identificatore univoco per l'attributo .

Esempio

L'esempio di codice seguente implementa la TypeId proprietà in una classe di parametri Attribute personalizzata e ne mostra l'uso.

// 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 output similar to the following:

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
*/

module NDP_UE_FS

open System

// Define a custom parameter attribute that takes a single message argument.
[<AttributeUsage(AttributeTargets.Parameter)>]
type ArgumentUsageAttribute(usageMsg) =
    inherit Attribute()
    
    let instanceGUID = Guid.NewGuid()
    
    // This is the Message property for the attribute.
    member val Message = usageMsg with get, set

    // Override TypeId to provide a unique identifier for the instance.
    override _.TypeId with get() =
        box instanceGUID

    // Override ToString() to append the message to what the base generates.
    override _.ToString() =
        base.ToString() + ":" + usageMsg

type TestClass() =
    // Assign an ArgumentUsage attribute to each parameter.
    // Assign a ParamArray attribute to strList using the params keyword.
    member _.TestMethod(
        [<ArgumentUsage "Must pass an array here.">]
        strArray: string [],
        [<ArgumentUsage "Can pass a param list or array here."; ParamArray>]
        strList: string []) = ()

let showAttributeTypeIds () =
    // Get the class type, and then get the MethodInfo object
    // for TestMethod to access its metadata.
    let clsType = typeof<TestClass>
    let mInfo = clsType.GetMethod "TestMethod"

    // There will be two elements in pInfoArray, one for each parameter.
    let pInfoArray = mInfo.GetParameters()
    if pInfoArray <> null then
        // Create an instance of the param array attribute on strList.
        let listArrayAttr =
            Attribute.GetCustomAttribute(pInfoArray[1], typeof<ParamArrayAttribute>)
            :?> ParamArrayAttribute

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

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

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

        // Display the attributes and corresponding TypeId values.
        printfn $"\n\"{listArrayAttr}\" \nTypeId: {listArrayAttr.TypeId}"

        printfn $"\n\"{arrayUsageAttr1}\" \nTypeId: {arrayUsageAttr1.TypeId}"
        printfn $"\n\"{arrayUsageAttr2}\" \nTypeId: {arrayUsageAttr2.TypeId}"
        printfn $"\n\"{listUsageAttr}\" \nTypeId: {listUsageAttr.TypeId}"
    else
        printfn $"The parameters information could not be retrieved for method {mInfo.Name}."

printfn "This example of the Attribute.TypeId property\ngenerates the following output."
printfn "\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 output similar to the following:
//
// 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_FS+ArgumentUsageAttribute:Must pass an array here."
// TypeId: d03a23f4-2536-4478-920f-8b0426dec7f1
//
// "NDP_UE_FS+ArgumentUsageAttribute:Must pass an array here."
// TypeId: a1b412e8-3047-49fa-8d03-7660d37ef718
//
// "NDP_UE_FS+ArgumentUsageAttribute:Can pass a param list or array here."
// TypeId: 7ac2bf61-0327-48d6-a07e-eb9aaf3dd45e

' Example for the Attribute.TypeId property.
Imports System.Reflection

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

        ' 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

    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
    End Class

    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

        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

    End Module ' AttributeTypeIdDemo
End Namespace ' NDP_UE_VB

' This example of the Attribute.TypeId property
' generates output similar to the following:
' 
' 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

Commenti

Come implementato, questo identificatore è semplicemente l'attributo Type . Tuttavia, è previsto che l'identificatore univoco venga usato per identificare due attributi dello stesso tipo.