ParameterInfo.IsDefined Method

Parameters

• attributeType
  Type: System.Type
  The type to search for.

• inherit
  Type: System.Boolean
  This parameter is ignored for objects of this type. See Remarks.

Return Value

Type: System.Boolean
true if one or more instances of attributeType or its derived types are applied to this parameter; otherwise, false.

Imports System.Reflection

' Define a custom attribute with one named parameter.
<AttributeUsage(AttributeTargets.Parameter)> _
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

' Derive another custom attribute from MyAttribute
<AttributeUsage(AttributeTargets.Parameter)> _
Public Class MyDerivedAttribute
   Inherits MyAttribute

   Public Sub New(ByVal name As String)
      MyBase.New(name)
   End Sub
End Class

' Define a class with a method that has three parameters. Apply
' MyAttribute to one parameter, MyDerivedAttribute to another, and
' no attributes to the third. 
Public Class MyClass1

   Public Sub MyMethod(<MyAttribute("This is an example parameter attribute")> _
                       ByVal i As Integer, _
                       <MyDerivedAttribute("This is another parameter attribute")> _
                       ByVal j As Integer, _
                       ByVal k As Integer)
      Return
   End Sub
End Class

Public Class Example

   Public Shared Sub Demo(ByVal outputBlock As System.Windows.Controls.TextBlock)
      ' Get the type of the class 'MyClass1'.
      Dim myType As Type = GetType(MyClass1)
      ' Get the members associated with the class 'MyClass1'.
      Dim myMethods As MethodInfo() = myType.GetMethods()

      ' For each method of the class 'MyClass1', display all the parameters
      ' to which MyAttribute or its derived types have been applied.
      For Each mi As MethodInfo In myMethods
         ' Get the parameters for the method.
         Dim myParameters As ParameterInfo() = mi.GetParameters()
         If myParameters.Length > 0 Then
            outputBlock.Text &= String.Format(vbCrLf & "The following parameters of {0} have MyAttribute or a derived type: ", mi) & vbCrLf
            For Each pi As ParameterInfo In myParameters
               If pi.IsDefined(GetType(MyAttribute), False) Then
                  outputBlock.Text &= String.Format("Parameter {0}, name = {1}, type = {2}", _
                      pi.Position, pi.Name, pi.ParameterType) & vbCrLf
               End If
            Next
         End If
      Next
   End Sub
End Class

' This code example produces the following output:
'
'The following parameters of Void MyMethod(Int32, Int32, Int32) have MyAttribute or a derived type:
'Parameter 0, name = i, type = System.Int32
'Parameter 1, name = j, type = System.Int32
'
'The following parameters of Boolean Equals(System.Object) have MyAttribute or a derived type:

using System;
using System.Reflection;

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

// Derive another custom attribute from MyAttribute
[AttributeUsage(AttributeTargets.Parameter)]
public class MyDerivedAttribute : MyAttribute
{
   public MyDerivedAttribute(string name) : base(name) { }
}

// Define a class with a method that has three parameters. Apply
// MyAttribute to one parameter, MyDerivedAttribute to another, and
// no attributes to the third. 
public class MyClass1
{
   public void MyMethod(
       [MyAttribute("This is an example parameter attribute")]
        int i,
       [MyDerivedAttribute("This is another parameter attribute")]
        int j,
       int k)
   {
      return;
   }
}

public class Example
{
   public static void Demo(System.Windows.Controls.TextBlock outputBlock)
   {
      // Get the type of the class 'MyClass1'.
      Type myType = typeof(MyClass1);
      // Get the members associated with the class 'MyClass1'.
      MethodInfo[] myMethods = myType.GetMethods();

      // For each method of the class 'MyClass1', display all the parameters
      // to which MyAttribute or its derived types have been applied.
      foreach (MethodInfo mi in myMethods)
      {
         // Get the parameters for the method.
         ParameterInfo[] myParameters = mi.GetParameters();
         if (myParameters.Length > 0)
         {
            outputBlock.Text += String.Format("\nThe following parameters of {0} have MyAttribute or a derived type: ", mi) + "\n";
            foreach (ParameterInfo pi in myParameters)
            {
               if (pi.IsDefined(typeof(MyAttribute), false))
               {
                  outputBlock.Text += String.Format("Parameter {0}, name = {1}, type = {2}",
                      pi.Position, pi.Name, pi.ParameterType) + "\n";
               }
            }
         }
      }
   }
}

/* This code example produces the following output:

The following parameters of Void MyMethod(Int32, Int32, Int32) have MyAttribute or a derived type:
Parameter 0, name = i, type = System.Int32
Parameter 1, name = j, type = System.Int32

The following parameters of Boolean Equals(System.Object) have MyAttribute or a derived type:
 */