MemberInfo.IsDefined(Type, Boolean) MemberInfo.IsDefined(Type, Boolean) MemberInfo.IsDefined(Type, Boolean) MemberInfo.IsDefined(Type, Boolean) Method

定義

在衍生類別中覆寫時,表示是否已有一個或多個具有指定型別或其衍生型別的屬性套用至這個成員。When overridden in a derived class, indicates whether one or more attributes of the specified type or of its derived types is applied to this member.

public:
 abstract bool IsDefined(Type ^ attributeType, bool inherit);
public abstract bool IsDefined (Type attributeType, bool inherit);
abstract member IsDefined : Type * bool -> bool
Public MustOverride Function IsDefined (attributeType As Type, inherit As Boolean) As Boolean

參數

attributeType
Type Type Type Type

要搜尋的自訂屬性型別。The type of custom attribute to search for. 此搜尋包括衍生型別。The search includes derived types.

inherit
Boolean Boolean Boolean Boolean

true 表示要搜尋這個成員的繼承鏈結以尋找屬性;否則為 falsetrue to search this member's inheritance chain to find the attributes; otherwise, false. 這個參數會忽略屬性和事件。This parameter is ignored for properties and events.

傳回

如果已有 attributeType 或其任何衍生型別的一個或多個執行個體套用至這個成員,則為 true,否則為 falsetrue if one or more instances of attributeType or any of its derived types is applied to this member; otherwise, false.

實作

範例

下列範例會判斷指定的屬性是否套用至指定的成員。The following example determines whether the specified attribute is applied to the specified member.

using namespace System;
using namespace System::Reflection;

// Define a custom attribute with one named parameter.

[AttributeUsage(AttributeTargets::All)]
public ref class MyAttribute: public Attribute
{
private:
   String^ myName;

public:
   MyAttribute( String^ name )
   {
      myName = name;
   }

   property String^ Name 
   {
      String^ get()
      {
         return myName;
      }
   }
};

// Define a class that has the custom attribute associated with one of its members.
public ref class MyClass1
{
public:

   [MyAttribute("This is an example attribute.")]
   void MyMethod( int i ){}
};

int main()
{
   try
   {
      // Get the type of MyClass1.
      Type^ myType = MyClass1::typeid;

      // Get the members associated with MyClass1.
      array<MemberInfo^>^myMembers = myType->GetMembers();

      // Display the attributes for each of the members of MyClass1.
      for ( int i = 0; i < myMembers->Length; i++ )
      {
         // Display the attribute if it is of type MyAttribute.
         if ( myMembers[ i ]->IsDefined( MyAttribute::typeid, false ) )
         {
            array<Object^>^myAttributes = myMembers[ i ]->GetCustomAttributes( MyAttribute::typeid, false );
            Console::WriteLine( "\nThe attributes of type MyAttribute for the member {0} are: \n", myMembers[ i ] );
            for ( int j = 0; j < myAttributes->Length; j++ )

               // Display the value associated with the attribute.
               Console::WriteLine( "The value of the attribute is : \"{0}\"",
                        (safe_cast<MyAttribute^>(myAttributes[ j ]))->Name );
         }
      }
   }
   catch ( Exception^ e ) 
   {
      Console::WriteLine( "An exception occurred: {0}", e->Message );
   }
}

using System;
using System.Reflection;

// Define a custom attribute with one named parameter.
[AttributeUsage(AttributeTargets.All)]
public class MyAttribute : Attribute
{
    private string myName;
    public MyAttribute(string name)
    {
        myName = name;
    }
    public string Name
    {
        get
        {
            return myName;
        }
    }
}

// Define a class that has the custom attribute associated with one of its members.
public class MyClass1
{
    [MyAttribute("This is an example attribute.")]
    public void MyMethod(int i)
    {
        return;
    }
}

public class MemberInfo_GetCustomAttributes_IsDefined
{
    public static void Main()
    {
        try
        {
            // Get the type of MyClass1.
            Type myType = typeof(MyClass1);
            // Get the members associated with MyClass1.
            MemberInfo[] myMembers = myType.GetMembers();

            // Display the attributes for each of the members of MyClass1.
            for(int i = 0; i < myMembers.Length; i++)
            {
                // Display the attribute if it is of type MyAttribute.
                if(myMembers[i].IsDefined(typeof(MyAttribute), false))
                {
                    Object[] myAttributes = myMembers[i].GetCustomAttributes(typeof(MyAttribute), false);
                    Console.WriteLine("\nThe attributes of type MyAttribute for the member {0} are: \n",
                        myMembers[i]);
                    for(int j = 0; j < myAttributes.Length; j++)
                        // Display the value associated with the attribute.
                        Console.WriteLine("The value of the attribute is : \"{0}\"",
                            ((MyAttribute)myAttributes[j]).Name);
                }
            }
        }
        catch(Exception e)
        {
            Console.WriteLine("An exception occurred: {0}", e.Message);
        }
    }
}
Imports System.Reflection

' Define a custom attribute with one named parameter.
<AttributeUsage(AttributeTargets.All)> Public Class MyAttribute
    Inherits Attribute
    Private myName As String

    Public Sub New(ByVal name As String)
        myName = name
    End Sub

    Public ReadOnly Property Name() As String
        Get
            Return myName
        End Get
    End Property
End Class 'MyAttribute

' Define a class that has the custom attribute associated with one of its members.
Public Class MyClass1

    <MyAttribute("This is an example attribute.")> Public Sub MyMethod(ByVal i As Integer)
        Return
    End Sub
End Class 'MyClass1

Public Class MemberInfo_GetCustomAttributes_IsDefined

    Public Shared Sub Main()
        Try
            ' Get the type of MyClass1.
            Dim myType As Type = GetType(MyClass1)
            ' Get the members associated with MyClass1.
            Dim myMembers As MemberInfo() = myType.GetMembers()

            ' Display the attributes for each of the members of MyClass1.
            Dim i As Integer
            For i = 0 To myMembers.Length - 1
                ' Display the attribute if it is of type MyAttribute.
                If myMembers(i).IsDefined(GetType(MyAttribute), False) Then
                    Dim myAttributes As [Object]() = myMembers(i).GetCustomAttributes(GetType(MyAttribute), False)
                    Console.WriteLine(ControlChars.Cr + "The attributes of type MyAttribute for the member {0} are: " + ControlChars.Cr, myMembers(i))
                    Dim j As Integer
                    For j = 0 To myAttributes.Length - 1
                        ' Display the value associated with the attribute.
                        Console.WriteLine("The value of the attribute is : ""{0}""", CType(myAttributes(j), MyAttribute).Name)
                    Next j
                End If
            Next i
        Catch e As Exception
            Console.WriteLine("An exception occurred: {0}", e.Message)
        End Try
    End Sub
End Class 'MemberInfo_GetCustomAttributes_IsDefined

備註

這個方法會忽略inherit屬性和事件的參數。This method ignores the inherit parameter for properties and events. 若要在繼承鏈中搜尋屬性和事件的屬性,請使用Attribute.IsDefined方法的適當多載。To search the inheritance chain for attributes on properties and events, use the appropriate overloads of the Attribute.IsDefined method.

注意

在 .NET Framework 版本2.0 中, true如果類型、方法或函式具有以新的元資料格式儲存的安全性屬性,則這個方法會傳回。In the .NET Framework version 2.0, this method returns true if a type, method, or constructor has security attributes stored in the new metadata format. 以2.0 版編譯的元件會使用此格式。Assemblies compiled with version 2.0 use this format. 使用舊版 .NET Framework 編譯的動態元件和元件會使用舊的 XML 格式。Dynamic assemblies and assemblies compiled with earlier versions of the .NET Framework use the old XML format. 請參閱發出宣告式安全性屬性See Emitting Declarative Security Attributes.

適用於