ImportedFromTypeLibAttribute Class
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ImportedFromTypeLibAttribute Class


Indicates that the types defined within an assembly were originally defined in a type library.

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


[AttributeUsageAttribute(AttributeTargets.Assembly, Inherited = false)]
public sealed class ImportedFromTypeLibAttribute : Attribute


Initializes a new instance of the ImportedFromTypeLibAttribute class with the name of the original type library file.


When implemented in a derived class, gets a unique identifier for this Attribute.(Inherited from Attribute.)


Gets the name of the original type library file.


This API supports the product infrastructure and is not intended to be used directly from your code. Returns a value that indicates whether this instance is equal to a specified object.(Inherited from Attribute.)


Returns the hash code for this instance.(Inherited from Attribute.)


Gets the Type of the current instance.(Inherited from Object.)


When overridden in a derived class, indicates whether the value of this instance is the default value for the derived class.(Inherited from Attribute.)


When overridden in a derived class, returns a value that indicates whether this instance equals a specified object.(Inherited from Attribute.)


Returns a string that represents the current object.(Inherited from Object.)

System_CAPS_pubinterfaceSystem_CAPS_privmethod_Attribute.GetIDsOfNames(Guid, IntPtr, UInt32, UInt32, IntPtr)

Maps a set of names to a corresponding set of dispatch identifiers.(Inherited from Attribute.)

System_CAPS_pubinterfaceSystem_CAPS_privmethod_Attribute.GetTypeInfo(UInt32, UInt32, IntPtr)

Retrieves the type information for an object, which can be used to get the type information for an interface.(Inherited from Attribute.)


Retrieves the number of type information interfaces that an object provides (either 0 or 1).(Inherited from Attribute.)

System_CAPS_pubinterfaceSystem_CAPS_privmethod_Attribute.Invoke(UInt32, Guid, UInt32, Int16, IntPtr, IntPtr, IntPtr, IntPtr)

Provides access to properties and methods exposed by an object.(Inherited from Attribute.)

You can apply this attribute to assemblies, although the Tlbimp.exe (Type Library Importer) typically applies it for you when it a type library.

The primary use of the attribute is to capture the original source of the type information. For example, you can import A.tlb as an interop assembly called A.dll and have assembly B.dll reference A.dll. When you export B.dll to B.tlb, this attribute causes the references in B.tlb that point to A.dll to point instead to A.tlb. This should not be confused with the ComImportAttribute, which specifies that an individual type is implemented in COM.

Legacy Code Example

using System;
using System.Reflection;
using System.Runtime.InteropServices;

namespace A
	class ClassA
		public static bool IsCOMAssembly( Assembly a )
			object[] AsmAttributes = a.GetCustomAttributes( typeof( ImportedFromTypeLibAttribute ), true );
			if( AsmAttributes.Length > 0 )
				ImportedFromTypeLibAttribute imptlb = ( ImportedFromTypeLibAttribute )AsmAttributes[0];
				string strImportedFrom  = imptlb.Value;

				// Print out the the name of the DLL from which the assembly is imported.
				Console.WriteLine( "Assembly " + a.FullName + " is imported from " + strImportedFrom );

				return true;
			// This is not a COM assembly.
			Console.WriteLine( "Assembly " + a.FullName + " is not imported from COM" );
			return false;

.NET Framework
Available since 1.1

Any public static (Shared in Visual Basic) members of this type are thread safe. Any instance members are not guaranteed to be thread safe.

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