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Attribute.GetCustomAttributes Method (ParameterInfo, Type)

Retrieves an array of the custom attributes 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 Attribute[] GetCustomAttributes (
	ParameterInfo element,
	Type attributeType
)
public static Attribute[] GetCustomAttributes (
	ParameterInfo element, 
	Type attributeType
)
public static function GetCustomAttributes (
	element : ParameterInfo, 
	attributeType : Type
) : Attribute[]

Parameters

element

An object derived from the ParameterInfo class that describes a parameter of a member of a class.

attributeType

The type, or a base type, of the custom attribute to search for.

Return Value

An Attribute array that contains the custom attributes of type attributeType applied to element, or an empty array if no such custom attributes exist.

Exception typeCondition

ArgumentNullException

element or attributeType is a null reference (Nothing in Visual Basic).

ArgumentException

attributeType is not derived from Attribute.

If element represents a parameter in a method of a derived type, the return value includes the inheritable custom attributes applied to the same parameter in the overridden base methods.

The following code example demonstrates the use of GetCustomAttributes, taking a ParameterInfo as a parameter.

using System;
using System.Reflection;
using System.ComponentModel;

namespace CustAttrs5CS {
    public class AClass {
        public void ParamArrayAndDesc(
            // Add ParamArray (with the keyword) and Description attributes.
            [Description("This argument is a ParamArray")]
            params int[] args)
        {}
    }

    class DemoClass {
        static void Main(string[] args) {
            // Get the Class type to access its metadata.
            Type clsType = typeof(AClass);
            // Get the type information for the method.
            MethodInfo mInfo = clsType.GetMethod("ParamArrayAndDesc");
            if (mInfo != null) {
                // Get the parameter information.
                ParameterInfo[] pInfo = mInfo.GetParameters();
                if (pInfo != null) {
                    // Iterate through all the attributes for the parameter.
                    foreach(Attribute attr in 
                        Attribute.GetCustomAttributes(pInfo[0])) {
                        // Check for the ParamArray attribute.
                        if (attr.GetType() == typeof(ParamArrayAttribute))
                            Console.WriteLine("Parameter {0} for method {1} " +
                                "has the ParamArray attribute.",
                                pInfo[0].Name, mInfo.Name);
                        // Check for the Description attribute.
                        else if (attr.GetType() == 
                            typeof(DescriptionAttribute)) {
                            Console.WriteLine("Parameter {0} for method {1} " +
                                "has a description attribute.",
                                pInfo[0].Name, mInfo.Name);
                            Console.WriteLine("The description is: \"{0}\"",
                                ((DescriptionAttribute)attr).Description);
                        }
                    }
                }
            }
        }
    }
}

/*
 * Output:
 * Parameter args for method ParamArrayAndDesc has a description attribute.
 * The description is: "This argument is a ParamArray"
 * Parameter args for method ParamArrayAndDesc has the ParamArray attribute.
 */

package CustAttrs5JSL; 
import System.*;
import System.Reflection.*;
import System.ComponentModel.*;

public class AClass
{
    public void ParamArrayAndDesc(
        // Add ParamArray (with the keyword) and Description attributes.
        /** @attribute Description("This argument is a ParamArray")
         */
        /** @attribute System.ParamArray() 
         */
        int args[])
    {
    } //ParamArrayAndDesc
} //AClass

class DemoClass
{
    public static void main(String[] args)
    {
        // Get the Class type to access its metadata.
        Type clsType = AClass.class.ToType();

        // Get the type information for the method.
        MethodInfo mInfo = clsType.GetMethod("ParamArrayAndDesc");
        if (mInfo != null) {
            // Get the parameter information.
            ParameterInfo pInfo[] = mInfo.GetParameters();
            if (pInfo != null) {
                // Iterate through all the attributes for the parameter.
                for (int iCtr = 0; iCtr < Attribute.GetCustomAttributes(
                    pInfo[0]).get_Length(); iCtr++) {
                    Attribute attr = (Attribute)Attribute.
                        GetCustomAttributes(pInfo[0]).get_Item(iCtr);
                    // Check for the ParamArray attribute.
                    if (attr.GetType().Equals(ParamArrayAttribute.class.
                        ToType())) {
                        Console.WriteLine("Parameter {0} for method {1} " 
                            + "has the ParamArray attribute.",
                            pInfo[0].get_Name(), mInfo.get_Name());
                    }
                    // Check for the Description attribute.
                    else {
                        if (attr.GetType().Equals(DescriptionAttribute.class.
                            ToType())) {
                            Console.WriteLine("Parameter {0} for method {1} " 
                                + "has a description attribute.", 
                                pInfo[0].get_Name(),mInfo.get_Name());
                            Console.WriteLine("The description is: \"{0}\"",
                                ((DescriptionAttribute)(attr)).
                                get_Description());
                        }
                    }
                }
            }
        }
    } //main
} //DemoClass   

/*
    Output:
    Parameter args for method ParamArrayAndDesc has a description attribute.
    The description is: "This argument is a ParamArray"
    Parameter args for method ParamArrayAndDesc has the ParamArray attribute.
*/

Windows 98, Windows 2000 SP4, Windows CE, Windows Millennium Edition, Windows Mobile for Pocket PC, Windows Mobile for Smartphone, Windows Server 2003, Windows XP Media Center Edition, Windows XP Professional x64 Edition, Windows XP SP2, Windows XP Starter Edition

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

.NET Framework

Supported in: 2.0, 1.1, 1.0

.NET Compact Framework

Supported in: 2.0, 1.0

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