.NET Framework Class Library
AttributeIsDefined Method (Assembly, Type)

Determines whether any custom attributes are applied to an assembly. Parameters specify the assembly, and the type of the custom attribute to search for.

Namespace:   System
Assembly:  mscorlib (in mscorlib.dll)
Syntax
Public Shared Function IsDefined ( _
	element As [%$TOPIC/20b27820_en-us_VS_110_1_0_0_0_0%], _
	attributeType As [%$TOPIC/20b27820_en-us_VS_110_1_0_0_0_1%] _
) As [%$TOPIC/20b27820_en-us_VS_110_1_0_0_0_2%]
public static [%$TOPIC/20b27820_en-us_VS_110_1_0_1_0_0%] IsDefined(
	[%$TOPIC/20b27820_en-us_VS_110_1_0_1_0_1%] element,
	[%$TOPIC/20b27820_en-us_VS_110_1_0_1_0_2%] attributeType
)
public:
static [%$TOPIC/20b27820_en-us_VS_110_1_0_2_0_0%] IsDefined(
	[%$TOPIC/20b27820_en-us_VS_110_1_0_2_0_1%]^ element, 
	[%$TOPIC/20b27820_en-us_VS_110_1_0_2_0_2%]^ attributeType
)
static member IsDefined : 
        element:[%$TOPIC/20b27820_en-us_VS_110_1_0_3_0_0%] * 
        attributeType:[%$TOPIC/20b27820_en-us_VS_110_1_0_3_0_1%] -> [%$TOPIC/20b27820_en-us_VS_110_1_0_3_0_2%]

Parameters

element
Type: System.ReflectionAssembly

An object derived from the Assembly class that describes a reusable collection of modules.

attributeType
Type: SystemType

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

Return Value

Type: SystemBoolean
true if a custom attribute of type attributeType is applied to element; otherwise, false.
Exceptions
ExceptionCondition
ArgumentNullException

element or attributeType is .

ArgumentException

attributeType is not derived from Attribute.

Remarks
NoteNote

Starting with 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 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.

Examples

The following code example illustrates the use of IsDefined, taking an Assembly as a parameter.

Imports System
Imports System.Reflection
Imports Microsoft.VisualBasic

' Add an AssemblyDescription attribute.
<Assembly: AssemblyDescription("A sample description")> 

Module DemoModule
    Sub Main()
        ' Get the assembly for this module. 
        Dim assy As System.Reflection.Assembly = GetType(DemoModule).Assembly
        ' Store the assembly name. 
        Dim assyName As String = assy.GetName().Name
        ' See if the AssemblyDescription attribute is defined. 
        If Attribute.IsDefined(assy, GetType(AssemblyDescriptionAttribute)) _
            Then 
            ' Affirm that the attribute is defined. Assume the filename of 
            ' this code example is "IsDef1VB".
            Console.WriteLine("The AssemblyDescription attribute is " & _
                "defined for assembly {0}.", assyName)
            ' Get the description attribute itself. 
            Dim attr As Attribute = Attribute.GetCustomAttribute( _
                assy, GetType(AssemblyDescriptionAttribute))
            ' Display the description. 
            If Not attr Is Nothing And _
                TypeOf attr Is AssemblyDescriptionAttribute Then 
                Dim adAttr As AssemblyDescriptionAttribute = _
                    CType(attr, AssemblyDescriptionAttribute)
                Console.WriteLine("The description is " & _
                    Chr(34) & "{0}" & Chr(34) & ".", adAttr.Description)
            Else
                Console.WriteLine("The description could not be retrieved.")
            End If 
        Else
            Console.WriteLine("The AssemblyDescription attribute is not " & _
                              "defined for assembly {0}.", assyName)
        End If 
    End Sub 
End Module 

' Output: 
' The AssemblyDescription attribute is defined for assembly IsDef1VB. 
' The description is "A sample description".
using System;
using System.Reflection;

// Add an AssemblyDescription attribute
[assembly: AssemblyDescription("A sample description")]
namespace IsDef1CS
{
    public class DemoClass
    {
        static void Main(string[] args)
        {
            // Get the class type to access its metadata.
            Type clsType = typeof(DemoClass);
            // Get the assembly object.
            Assembly assy = clsType.Assembly;
            // Store the assembly's name.
            String assyName = assy.GetName().Name;
            // See if the Assembly Description is defined. 
            bool isdef = Attribute.IsDefined(assy, 
                typeof(AssemblyDescriptionAttribute));
            if (isdef)
            {
                // Affirm that the attribute is defined.
                Console.WriteLine("The AssemblyDescription attribute " +
                    "is defined for assembly {0}.", assyName);
                // Get the description attribute itself.
                AssemblyDescriptionAttribute adAttr = 
                    (AssemblyDescriptionAttribute)Attribute.GetCustomAttribute(
                    assy, typeof(AssemblyDescriptionAttribute));
                // Display the description. 
                if (adAttr != null)
                    Console.WriteLine("The description is \"{0}\".", 
                        adAttr.Description);
                else
                    Console.WriteLine("The description could not " +
                        "be retrieved.");            
            }
            else
                Console.WriteLine("The AssemblyDescription attribute is not " +
                    "defined for assembly {0}.", assyName);
        }
    }
}

/*
 * Output:
 * The AssemblyDescription attribute is defined for assembly IsDef1CS.
 * The description is "A sample description".
 */
using namespace System;
using namespace System::Reflection;

// Add an AssemblyDescription attribute
[assembly:AssemblyDescription("A sample description")];
namespace IsDef1CS
{
   ref class DemoClass
   {
   public:
      static void Main()
      {

         // Get the class type to access its metadata.
         Type^ clsType = DemoClass::typeid;

         // Get the assembly object.
         Assembly^ assy = clsType->Assembly;

         // Store the assembly's name.
         String^ assyName = assy->GetName()->Name;

         //Type assyType = assy.GetType(); 
         // See if the Assembly Description is defined. 
         bool isdef = Attribute::IsDefined( assy, AssemblyDescriptionAttribute::typeid );
         if ( isdef )
         {

            // Affirm that the attribute is defined.
            Console::WriteLine( "The AssemblyDescription attribute " 
            "is defined for assembly {0}.", assyName );

            // Get the description attribute itself.
            AssemblyDescriptionAttribute^ adAttr = dynamic_cast<AssemblyDescriptionAttribute^>(Attribute::GetCustomAttribute( assy, AssemblyDescriptionAttribute::typeid ));

            // Display the description. 
            if ( adAttr != nullptr )
                        Console::WriteLine( "The description is \"{0}\".", adAttr->Description );
            else
                        Console::WriteLine( "The description could not " 
            "be retrieved." );
         }
         else
                  Console::WriteLine( "The AssemblyDescription attribute is not " 
         "defined for assembly {0}.", assyName );
      }

   };

}


/*
 * Output:
 * The AssemblyDescription attributeis defined for assembly IsDef1CS.
 * The description is "A sample description".
 */
Version Information

.NET Framework

Supported in: 4.5.2, 4.5.1, 4.5, 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

.NET for Windows Phone apps

Supported in: Windows Phone 8.1, Windows Phone 8, Silverlight 8.1
Platforms

Windows Phone 8.1, Windows Phone 8, Windows 8.1, Windows Server 2012 R2, Windows 8, Windows Server 2012, Windows 7, Windows Vista SP2, Windows Server 2008 (Server Core Role not supported), Windows Server 2008 R2 (Server Core Role supported with SP1 or later; Itanium not supported)

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