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CustomAttributeData.GetCustomAttributes Method (Assembly)

Note: This method is new in the .NET Framework version 2.0.

Returns a list of CustomAttributeData objects representing data about the attributes that have been applied to the target assembly.

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

public static IList<CustomAttributeData> GetCustomAttributes (
	Assembly target
)
public static IList<CustomAttributeData> GetCustomAttributes (
	Assembly target
)
public static function GetCustomAttributes (
	target : Assembly
) : IList<CustomAttributeData>

Parameters

target

The assembly whose custom attribute data is to be retrieved.

Return Value

An IList of CustomAttributeData objects representing data about the attributes that have been applied to the target assembly.

Exception typeCondition

ArgumentNullException

target is a null reference (Nothing in Visual Basic).

This method provides an alternative to the GetCustomAttributes method that can always be used in the Reflection-only context.

The following code example defines a custom attribute with two constructors and one property. The attribute is applied to the assembly, to a type declared in the assembly, to a method of the type, and to a parameter of the method. When executed, the assembly loads itself into the reflection-only context and displays the custom attributes.

The GetCustomAttributes method is used in Main() to get the custom attributes applied to the assembly. The return value of the method is passed to the ShowAttributeData method.

using System;
using System.Reflection;
using System.Collections.Generic;

// The example attribute is applied to the assembly.
[assembly:Example(ExampleKind.ThirdKind, Note="This is a note on the assembly.")]

// An enumeration used by the ExampleAttribute class.
public enum ExampleKind
{
    FirstKind, 
    SecondKind, 
    ThirdKind, 
    FourthKind
};

// An example attribute. The attribute can be applied to all
// targets, from assemblies to parameters.
//
[AttributeUsage(AttributeTargets.All)]
public class ExampleAttribute : Attribute
{
    // Data for properties.
    private ExampleKind kindValue;
    private string noteValue;

    // Constructors. The parameterless constructor (.ctor) calls
    // the constructor that specifies ExampleKind, and supplies the
    // default value.
    //
    public ExampleAttribute(ExampleKind initKind)
    {
        kindValue = initKind;
    }
    public ExampleAttribute() : this(ExampleKind.FirstKind) {}

    // Properties. The Note property must be read/write, so that it
    // can be used as a named parameter.
    //
    public ExampleKind Kind { get { return kindValue; }}
    public string Note    
    {
        get { return noteValue; }
        set { noteValue = value; }
    }
}

// The example attribute is applied to the test class.
//
[Example(ExampleKind.SecondKind, Note="This is a note on the class.")]
public class Test
{
    // The example attribute is applied to a method, using the
    // parameterless constructor and supplying a named argument.
    // The attribute is also applied to the method parameter.
    //
    [Example(Note="This is a note on a method.")]
    public void TestMethod([Example] object arg) { }

    // Main() gets objects representing the assembly, the test
    // type, the test method, and the method parameter. Custom
    // attribute data is displayed for each of these.
    //
    public static void Main()
    {
        Assembly asm = Assembly.ReflectionOnlyLoad("Source");
        Type t = asm.GetType("Test");
        MethodInfo m = t.GetMethod("TestMethod");
        ParameterInfo[] p = m.GetParameters();

        Console.WriteLine("\r\nAttributes for assembly: {0}", asm);
        ShowAttributeData(CustomAttributeData.GetCustomAttributes(asm));
        Console.WriteLine("\r\nAttributes for type: {0}", t);
        ShowAttributeData(CustomAttributeData.GetCustomAttributes(t));
        Console.WriteLine("\r\nAttributes for member: {0}", m);
        ShowAttributeData(CustomAttributeData.GetCustomAttributes(m));
        Console.WriteLine("\r\nAttributes for parameter: {0}", p);
        ShowAttributeData(CustomAttributeData.GetCustomAttributes(p[0]));
    }

    private static void ShowAttributeData(
        IList<CustomAttributeData> attributes)
    {
        foreach( CustomAttributeData cad in attributes )
        {
            Console.WriteLine("   {0}", cad);
            Console.WriteLine("      Constructor: {0}", cad.Constructor);

            Console.WriteLine("      Constructor arguments:");
            foreach( CustomAttributeTypedArgument cata 
                in cad.ConstructorArguments )
            {
                Console.WriteLine("         Type: {0} Value: {1}", 
                    cata.ArgumentType, cata.Value);
            }

            Console.WriteLine("      Named arguments:");
            foreach( CustomAttributeNamedArgument cana 
                in cad.NamedArguments )
            {
                CustomAttributeTypedArgument cata = cana.TypedValue;
                Console.WriteLine("         MemberInfo: {0}", 
                    cana.MemberInfo);
                Console.WriteLine("         Type: {0} Value: {1}", 
                    cata.ArgumentType, cata.Value);
            }
        }
    }
}

/* This code example produces output similar to the following:

Attributes for assembly: source, Version=0.0.0.0, Culture=neutral, PublicKeyToken=null
   [ExampleAttribute((ExampleKind)2, Note = "This is a note on the assembly.")]
      Constructor: Void .ctor(ExampleKind)
      Constructor arguments:
         Type: ExampleKind Value: 2
      Named arguments:
         MemberInfo: System.String Note
         Type: System.String Value: This is a note on the assembly.
   [System.Runtime.CompilerServices.CompilationRelaxationsAttribute((Int32)8)]
      Constructor: Void .ctor(Int32)
      Constructor arguments:
         Type: System.Int32 Value: 8
      Named arguments:

Attributes for type: Test
   [ExampleAttribute((ExampleKind)1, Note = "This is a note on the class.")]
      Constructor: Void .ctor(ExampleKind)
      Constructor arguments:
         Type: ExampleKind Value: 1
      Named arguments:
         MemberInfo: System.String Note
         Type: System.String Value: This is a note on the class.

Attributes for member: Void TestMethod(System.Object)
   [ExampleAttribute(Note = "This is a note on a method.")]
      Constructor: Void .ctor()
      Constructor arguments:
      Named arguments:
         MemberInfo: System.String Note
         Type: System.String Value: This is a note on a method.

Attributes for parameter: System.Object arg
   [ExampleAttribute()]
      Constructor: Void .ctor()
      Constructor arguments:
      Named arguments:
*/

Windows 98, Windows 2000 SP4, Windows Millennium Edition, 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

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