IsDefined Method (ParameterInfo, Type)

Attribute.IsDefined Method (ParameterInfo, Type)

Determines whether any custom attributes are applied to a method parameter. Parameters specify the method parameter, and the type of the custom attribute to search for.

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

public static bool IsDefined(
	ParameterInfo element,
	Type attributeType


Type: System.Reflection.ParameterInfo
An object derived from the ParameterInfo class that describes a parameter of a member of a class.
Type: System.Type
The type, or a base type, of the custom attribute to search for.

Return Value

Type: System.Boolean
true if a custom attribute of type attributeType is applied to element; otherwise, false.


element or attributeType is null.


attributeType is not derived from Attribute.

The ancestors of element are searched for custom attributes.

The following code example illustrates the use of IsDefined, taking a ParameterInfo as a parameter.

using System;
using System.Reflection;

namespace IsDef5CS 
    public class TestClass 
        // Assign a ParamArray attribute to the parameter using the keyword.
        public void Method1(params String[] args)

    public class DemoClass 
        static void Main(string[] args) 
            // Get the class type to access its metadata.
            Type clsType = typeof(TestClass);
            // Get the MethodInfo object for Method1.
            MethodInfo mInfo = clsType.GetMethod("Method1");
            // Get the ParameterInfo array for the method parameters.
            ParameterInfo[] pInfo = mInfo.GetParameters();
            if (pInfo != null) 
                // See if the ParamArray attribute is defined.
                bool isDef = Attribute.IsDefined(pInfo[0], 
                // Display the result.
                Console.WriteLine("The ParamArray attribute {0} defined for " +
                                  "parameter {1} of method {2}.",
                                  isDef ? "is" : "is not",
                Console.WriteLine("The parameters information could " +
                            "not be retrieved for method {0}.", mInfo.Name);

 * Output:
 * The ParamArray attribute is defined for parameter args of method Method1.

.NET Framework

Supported in: 4, 3.5, 3.0, 2.0, 1.1, 1.0

.NET Framework Client Profile

Supported in: 4, 3.5 SP1

Portable Class Library

Supported in: Portable Class Library

Windows 7, Windows Vista SP1 or later, Windows XP SP3, Windows XP SP2 x64 Edition, Windows Server 2008 (Server Core not supported), Windows Server 2008 R2 (Server Core supported with SP1 or later), Windows Server 2003 SP2

The .NET Framework does not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.

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