System.Runtime.InteropServi ...


.NET Framework Class Library
ComImportAttribute Class

Indicates that the attributed type was previously defined in COM.

Namespace:  System.Runtime.InteropServices
Assembly:  mscorlib (in mscorlib.dll)
Syntax
Visual Basic (Declaration) 
<AttributeUsageAttribute(AttributeTargets.Class Or AttributeTargets.Interface, Inherited := False)> _
<ComVisibleAttribute(True)> _
Public NotInheritable Class ComImportAttribute _
    Inherits Attribute
Visual Basic (Usage) 
Dim instance As ComImportAttribute
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
JScript 
public final class ComImportAttribute extends Attribute
Remarks

You can apply this attribute to classes or interfaces, although the Type Library Importer (Tlbimp.exe) 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.

NoteNote:

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();
   }
};
Inheritance Hierarchy
System..::.Object
  System..::.Attribute
    System.Runtime.InteropServices..::.ComImportAttribute
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.
Platforms

Windows 7, Windows Vista, Windows XP SP2, Windows XP Media Center Edition, Windows XP Professional x64 Edition, Windows XP Starter Edition, Windows Server 2008 R2, Windows Server 2008, Windows Server 2003, Windows Server 2000 SP4, Windows Millennium Edition, Windows 98, Windows CE, Windows Mobile for Smartphone, Windows Mobile for Pocket PC

The .NET Framework and .NET Compact Framework do not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.
Version Information

.NET Framework

Supported in: 3.5, 3.0, 2.0, 1.1, 1.0

.NET Compact Framework

Supported in: 3.5, 2.0
See Also

Reference

ComImportAttribute Members
System.Runtime.InteropServices Namespace

Other Resources

Type Library Importer (Tlbimp.exe)
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