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Assembly.IsDefined Method

Indicates whether or not a specified attribute has been applied to the assembly.

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

public virtual bool IsDefined(
	Type attributeType,
	bool inherit


Type: System.Type
The type of the attribute to be checked for this assembly.
Type: System.Boolean
This argument is ignored for objects of this type.

Return Value

Type: System.Boolean
true if the attribute has been applied to the assembly; otherwise, false.


_Assembly.IsDefined(Type, Boolean)
ICustomAttributeProvider.IsDefined(Type, Boolean)


attributeType is null.


attributeType uses an invalid type.


In the .NET Framework version 2.0, this method returns true if the assembly has security attributes stored in the new metadata format. Assemblies compiled with version 2.0 use this 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 applies the AssemblyTitleAttribute attribute to an assembly and then uses IsDefined to indicate whether it was applied. It also tests an attribute that was not applied.

using System;
using System.Reflection;

// Set an assembly attribute.
[assembly:AssemblyTitleAttribute("A title example")]

// Note that the suffix "Attribute" can be omitted:
// [assembly:AssemblyTitle("A title example")]

public class Test {

    public static void Main() {

        // Get the assembly that is executing this method.
        Assembly asm = Assembly.GetCallingAssembly();

        // Get the attribute type just defined.
        Type aType = typeof(AssemblyTitleAttribute);
        Console.WriteLine(asm.IsDefined(aType, false));

        // Try an attribute not defined.
        aType = typeof(AssemblyVersionAttribute);
        Console.WriteLine(asm.IsDefined(aType, false));
//  This code example produces the following output:
//  True
//  False

.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.