Attribute.GetCustomAttribute Method (MemberInfo, Type, Boolean)

Retrieves a custom attribute applied to a member of a type. Parameters specify the member, the type of the custom attribute to search for, and whether to search ancestors of the member.

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

public static Attribute GetCustomAttribute (
	MemberInfo element,
	Type attributeType,
	bool inherit
)
public static Attribute GetCustomAttribute (
	MemberInfo element, 
	Type attributeType, 
	boolean inherit
)
public static function GetCustomAttribute (
	element : MemberInfo, 
	attributeType : Type, 
	inherit : boolean
) : Attribute
Not applicable.

Parameters

element

An object derived from the MemberInfo class that describes a constructor, event, field, method, or property member of a class.

attributeType

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

inherit

If true, specifies to also search the ancestors of element for custom attributes.

Return Value

A reference to the single custom attribute of type attributeType that is applied to element, or a null reference (Nothing in Visual Basic) if there is no such attribute.

Exception typeCondition

ArgumentNullException

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

ArgumentException

attributeType is not derived from Attribute.

NotSupportedException

element is not a constructor, method, property, event, type, or field.

AmbiguousMatchException

More than one of the requested attributes was found.

TypeLoadException

A custom attribute type cannot be loaded.

NoteNote:

Starting with the .NET Framework version 2.0, this method returns security attributes on types, methods, and constructors if the attributes are stored in the new metadata format. Assemblies compiled with version 2.0 or later use the new format. Dynamic assemblies and assemblies compiled with earlier versions of the .NET Framework use the old XML format. See Emitting Declarative Security Attributes.

The following code example illustrates the use of the GetCustomAttribute method taking a MemberInfo as a parameter.

using System;
using System.Reflection;

namespace IsDef4CS 
{
    public class TestClass 
    {
        // Assign the Obsolete attribute to a method.
        [Obsolete("This method is obsolete. Use Method2 instead.")]
        public void Method1()
        {}
        public void Method2()
        {}
    }

    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");
            // See if the Obsolete attribute is defined for this method.
            bool isDef = Attribute.IsDefined(mInfo, typeof(ObsoleteAttribute));
            // Display the result.
            Console.WriteLine("The Obsolete Attribute {0} defined for {1} of class {2}.",
                isDef ? "is" : "is not", mInfo.Name, clsType.Name);
            // If it's defined, display the attribute's message.
            if (isDef) 
            {
                ObsoleteAttribute obsAttr = 
                                 (ObsoleteAttribute)Attribute.GetCustomAttribute( 
                                                    mInfo, typeof(ObsoleteAttribute));
                if (obsAttr != null)
                    Console.WriteLine("The message is: \"{0}\".",
                        obsAttr.Message);
                else
                    Console.WriteLine("The message could not be retrieved.");
            }
        }
    }
}

/*
 * Output:
 * The Obsolete Attribute is defined for Method1 of class TestClass.
 * The message is: "This method is obsolete. Use Method2 instead.".
 */

package IsDef4CS;

import System.*;
import System.Reflection.*;
public class TestClass
{
    // Assign the Obsolete attribute to a method.
    /** @attribute Obsolete("This method is obsolete. Use Method2 instead.")
     */
    public void Method1()
    {
    } //Method1

    public void Method2()
    {
    } //Method2
} //TestClass

class DemoClass
{
    public static void main(String[] args)
    {
        // Get the class type to access its metadata.
        Type clsType = TestClass.class.ToType();
        // Get the MethodInfo object for Method1.
        MethodInfo mInfo = clsType.GetMethod("Method1");
        // See if the Obsolete attribute is defined for this method.
        boolean isDef = Attribute.IsDefined(mInfo, 
            ObsoleteAttribute.class.ToType());
        // Display the result.
        Console.WriteLine("The Obsolete Attribute {0} defined for {1} of class {2}.",
            (isDef) ? "is" : "is not", mInfo.get_Name(), clsType.get_Name());
        // If it's defined, display the attribute's message.
        if (isDef) {
            ObsoleteAttribute obsAttr = (ObsoleteAttribute)
                (Attribute.GetCustomAttribute(mInfo, 
                    ObsoleteAttribute.class.ToType()));
            if (obsAttr != null) {
                Console.WriteLine("The message is: \"{0}\".", 
                    obsAttr.get_Message());
            }
            else {
                Console.WriteLine("The message could not be retrieved.");
            }
        }
    } //main
} //DemoClass

/*
   Output:
   The Obsolete Attribute is defined for Method1 of class TestClass.
   The message is: "This method is obsolete. Use Method2 instead.".
*/

import System;
import System.Reflection;

package IsDef4JS {
    public class TestClass {
	    // Assign the Obsolete attribute to a method.
	    Obsolete("This method is obsolete. Use Method2 instead.") public function Method1() : void 
	    {}

	    public function Method2() : void
	    {}
    }

    class DemoClass {
	static function Main() : void {
	    // Get the class type to access its metadata.
	    var clsType : Type = TestClass;
	    // Get the MethodInfo object for Method1.
	    var mInfo : MethodInfo = clsType.GetMethod("Method1");
	    // See if the Obsolete attribute is defined for this method.
	    var isDef : boolean = Attribute.IsDefined(mInfo, ObsoleteAttribute);
	    // Display the result.
	    Console.WriteLine("The Obsolete Attribute {0} defined for {1} of class {2}.",
		    isDef ? "is" : "is not", mInfo.Name, clsType.Name);
	    // If it's defined, display the attribute's message.
	    if (isDef) {
		var obsAttr : ObsoleteAttribute = ObsoleteAttribute(Attribute.GetCustomAttribute(mInfo, ObsoleteAttribute));
		if (obsAttr != null)
    		    Console.WriteLine("The message is: \"{0}\".",
				obsAttr.Message);
		else
		    Console.WriteLine("The message could not be retrieved.");
	    }
	}
    }
}
IsDef4JS.DemoClass.Main();

/*
 * Output:
 * The Obsolete Attribute is defined for Method1 of class TestClass.
 * The message is: "This method is obsolete. Use Method2 instead.".
 */

Windows 98, Windows Server 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 Microsoft .NET Framework 3.0 is supported on Windows Vista, Microsoft Windows XP SP2, and Windows Server 2003 SP1.

.NET Framework

Supported in: 3.0, 2.0, 1.1, 1.0

.NET Compact Framework

Supported in: 2.0, 1.0

XNA Framework

Supported in: 1.0

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