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ParameterInfo.IsDefined Method

Determines whether the custom attribute of the specified type or its derived types is applied to this parameter.

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

public virtual bool IsDefined(
	Type attributeType,
	bool inherit


Type: System.Type
The Type object to search for.
Type: System.Boolean
This argument 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.


ICustomAttributeProvider.IsDefined(Type, Boolean)


attributeType is null.


attributeType is not a Type object supplied by the common language runtime.

This method ignores the inherit parameter. To search the inheritance chain for attributes on parameters, use the appropriate overloads of the Attribute.IsDefined method.

The following example defines two custom attributes, MyAttribute and MyDerivedAttribute. MyDerivedAttribute is derived from MyAttribute. The example then applies these attributes to the parameters of a method of an example class.

When the example is run, it uses the IsDefined method to test all parameters of all methods in the example class. It then displays the parameters that have MyAttribute or MyDerivedAttribute.

using System;
using System.Reflection;

// Define a custom attribute with one named parameter.
public class MyAttribute : Attribute
    private string myName;
    public MyAttribute(string name)
        myName = name;
    public string Name 
            return myName;

// Derive another custom attribute from MyAttribute
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 )

public class MemberInfo_GetCustomAttributes 
    public static void Main()
        // 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)
                Console.WriteLine("\nThe following parameters of {0} have MyAttribute or a derived type: ", mi);
                foreach (ParameterInfo pi in myParameters)
                    if (pi.IsDefined(typeof(MyAttribute), false))
                        Console.WriteLine("Parameter {0}, name = {1}, type = {2}", 
                            pi.Position, pi.Name, pi.ParameterType);

/* 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:

.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.