ComImportAttribute Class (System.Runtime.InteropServices)

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.NET Framework Class Library
ComImportAttribute Class

Indicates that the attributed type was previously defined in COM.

Inheritance Hierarchy

System.Object
  System.Attribute
    System.Runtime.InteropServices.ComImportAttribute

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

Visual Basic
<AttributeUsageAttribute(AttributeTargets.Class Or AttributeTargets.Interface, Inherited := False)> _
<ComVisibleAttribute(True)> _
Public NotInheritable Class ComImportAttribute _
	Inherits Attribute
C#
[AttributeUsageAttribute(AttributeTargets.Class|AttributeTargets.Interface, Inherited = false)]
[ComVisibleAttribute(true)]
public sealed class ComImportAttribute : Attribute
Visual C++
[AttributeUsageAttribute(AttributeTargets::Class|AttributeTargets::Interface, Inherited = false)]
[ComVisibleAttribute(true)]
public ref class ComImportAttribute sealed : public Attribute
F#
[<Sealed>]
[<AttributeUsageAttribute(AttributeTargets.Class|AttributeTargets.Interface, Inherited = false)>]
[<ComVisibleAttribute(true)>]
type ComImportAttribute =  
    class
        inherit Attribute
    end

The ComImportAttribute type exposes the following members.

Constructors

  Name Description
Public method ComImportAttribute Initializes a new instance of the ComImportAttribute.
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Properties

  Name Description
Public property TypeId When implemented in a derived class, gets a unique identifier for this Attribute. (Inherited from Attribute.)
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Methods

  Name Description
Public method Equals Infrastructure. Returns a value that indicates whether this instance is equal to a specified object. (Inherited from Attribute.)
Protected method Finalize Allows an object to try to free resources and perform other cleanup operations before it is reclaimed by garbage collection. (Inherited from Object.)
Public method GetHashCode Returns the hash code for this instance. (Inherited from Attribute.)
Public method GetType Gets the Type of the current instance. (Inherited from Object.)
Public method IsDefaultAttribute When overridden in a derived class, indicates whether the value of this instance is the default value for the derived class. (Inherited from Attribute.)
Public method Match When overridden in a derived class, returns a value that indicates whether this instance equals a specified object. (Inherited from Attribute.)
Protected method MemberwiseClone Creates a shallow copy of the current Object. (Inherited from Object.)
Public method ToString Returns a string that represents the current object. (Inherited from Object.)
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Explicit Interface Implementations

  Name Description
Explicit interface implemetation Private method _Attribute.GetIDsOfNames Maps a set of names to a corresponding set of dispatch identifiers. (Inherited from Attribute.)
Explicit interface implemetation Private method _Attribute.GetTypeInfo Retrieves the type information for an object, which can be used to get the type information for an interface. (Inherited from Attribute.)
Explicit interface implemetation Private method _Attribute.GetTypeInfoCount Retrieves the number of type information interfaces that an object provides (either 0 or 1). (Inherited from Attribute.)
Explicit interface implemetation Private method _Attribute.Invoke Provides access to properties and methods exposed by an object. (Inherited from Attribute.)
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Remarks

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

ComImportAttribute is a pseudo-custom attribute that indicates that a type has been defined in a previously published type library. The common language runtime treats these types differently when activating, exporting, coercing, and so on.

Note Note

All base COM types that are inherited by a managed object must aggregate the Free Threaded Marshaller (FTM). COM types that do not aggregate the FTM can't be inherited by managed objects.

Examples

The following example demonstrates how to apply the ComImportAttribute to a managed interface declaration. You apply this attribute only when generating an interop assembly manually in source code, and want to simulate the metadata produced by Tlbimp.exe.

Visual Basic

Imports System
Imports System.Runtime.InteropServices

Module MyModule
	' If you do not have a type library for an interface
	' you can redeclare it using ComImportAttribute.

	' This is how the interface would look in an idl file.

	'[
	'object,
	'uuid("73EB4AF8-BE9C-4b49-B3A4-24F4FF657B26"),
	'dual,	helpstring("IMyStorage Interface"),
	'pointer_default(unique)
	']
	'interface IMyStorage : IDispatch
	'{
	'	[id(1)]
	'	HRESULT GetItem([in] BSTR bstrName, [out, retval] IDispatch ** ppItem);
	'	[id(2)]
	'	HRESULT GetItems([in] BSTR bstrLocation, [out] SAFEARRAY(VARIANT)* pItems);
	'	[id(3)]
	'	HRESULT GetItemDescriptions([in] BSTR bstrLocation, [out] SAFEARRAY(VARIANT) ** ppItems);
	'	[id(4), propget]
	'	HRESULT get_IsEmpty([out, retval] BOOL * pfEmpty);
	'};

	' This is the managed declaration.

	<ComImport(), Guid("73EB4AF8-BE9C-4b49-B3A4-24F4FF657B26")> _
	Public Interface IMyStorage
		<DispId(1)> _
		Function GetItem(<InAttribute(), MarshalAs(UnmanagedType.BStr)> ByVal bstrName As String) _
		   As <MarshalAs(UnmanagedType.Interface)> Object

		<DispId(2)> _
		Function GetItems(<InAttribute(), MarshalAs(UnmanagedType.BStr)> ByVal bstrLocation As String, _
		   <OutAttribute(), MarshalAs(UnmanagedType.SafeArray)> ByVal Items() As Object)


		<DispId(3)> _
		Function GetItemDescriptions(<InAttribute()> ByVal bstrLocation As String, _
		  <InAttribute(), OutAttribute(), MarshalAs(UnmanagedType.SafeArray)> ByRef varDescriptions() As Object)

		<DispId(4)> _
		ReadOnly Property IsEmpty(<MarshalAs(UnmanagedType.VariantBool)> ByVal bEmpty As Boolean)

	End Interface
End Module


C#

using System;
using System.Runtime.InteropServices;

namespace MyModule
{
	// If you do not have a type library for an interface
	// you can redeclare it using ComImportAttribute.

	// This is how the interface would look in an idl file.

	//[
	//object,
	//uuid("73EB4AF8-BE9C-4b49-B3A4-24F4FF657B26"),
	//dual,	helpstring("IMyStorage Interface"),
	//pointer_default(unique)
	//]
	//interface IMyStorage : IDispatch
	//{
	//	[id(1)]
	//	HRESULT GetItem([in] BSTR bstrName, [out, retval] IDispatch ** ppItem);
	//	[id(2)]
	//	HRESULT GetItems([in] BSTR bstrLocation, [out] SAFEARRAY(VARIANT)* pItems);
	//	[id(3)]
	//	HRESULT GetItemDescriptions([in] BSTR bstrLocation, [out] SAFEARRAY(VARIANT) ** ppItems);
	//	[id(4), propget]
	//	HRESULT get_IsEmpty([out, retval] BOOL * pfEmpty);
	//};

	// This is the managed declaration.

	[ComImport]
	[Guid("73EB4AF8-BE9C-4b49-B3A4-24F4FF657B26")]
	public interface IMyStorage  
	{
		[DispId(1)]
		[return : MarshalAs( UnmanagedType.Interface )]
		Object GetItem( [In, MarshalAs( UnmanagedType.BStr )] String bstrName );

		[DispId(2)]
		void GetItems( [In, MarshalAs( UnmanagedType.BStr )] String bstrLocation, 
			[Out, MarshalAs( UnmanagedType.SafeArray, 
					  SafeArraySubType = VarEnum.VT_VARIANT )] out Object[] Items );


		[DispId(3)]
		void GetItemDescriptions( [In] String bstrLocation, 
			[In, Out, MarshalAs( UnmanagedType.SafeArray )] ref Object[] varDescriptions );

		bool IsEmpty 
		{
			[DispId(4)]
			[return : MarshalAs( UnmanagedType.VariantBool )]
			get;
		}
	}
}


Visual C++

using namespace System;
using namespace System::Runtime::InteropServices;

// If you do not have a type library for an interface
// you can redeclare it using ComImportAttribute.
// This is how the interface would look in an idl file.
//[
//object,
//uuid("73EB4AF8-BE9C-4b49-B3A4-24F4FF657B26"),
//dual, helpstring("IMyStorage Interface"),
//pointer_default(unique)
//]
//interface IMyStorage : IDispatch
//{
// [id(1)]
// HRESULT GetItem([in] BSTR bstrName, [out, retval] IDispatch ** ppItem);
// [id(2)]
// HRESULT GetItems([in] BSTR bstrLocation, [out] SAFEARRAY(VARIANT)* pItems);
// [id(3)]
// HRESULT GetItemDescriptions([in] BSTR bstrLocation, [out] SAFEARRAY(VARIANT) ** ppItems);
// [id(4), propget]
// HRESULT get_IsEmpty([out, retval] BOOL * pfEmpty);
//};
// This is the managed declaration.

[ComImport]
[Guid("73EB4AF8-BE9C-4b49-B3A4-24F4FF657B26")]
interface class IMyStorage
{
   [DispId(1)]
   Object^ GetItem( [In,MarshalAs(UnmanagedType::BStr)]String^ bstrName );

   //[return : MarshalAs(UnmanagedType::Interface)]

   [DispId(2)]
   void GetItems( [In,MarshalAs(UnmanagedType::BStr)]String^ bstrLocation, [Out,MarshalAs(UnmanagedType::SafeArray,
   SafeArraySubType=VarEnum::VT_VARIANT)]array<Object^>^Items );

   [DispId(3)]
   void GetItemDescriptions( [In]String^ bstrLocation, [In,Out,MarshalAs(UnmanagedType::SafeArray)]array<Object^>^varDescriptions );

   property bool IsEmpty 
   {
      [DispId(4)]
      [returnvalue:MarshalAs(UnmanagedType::VariantBool)]
      bool get();
   }
};


Version Information

.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
Platforms

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.
Thread Safety

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

Reference

Other Resources