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ComImportAttribute Class

Indicates that the attributed type was previously defined in COM.


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

<AttributeUsageAttribute(AttributeTargets.Class Or AttributeTargets.Interface, Inherited := False)> _
Public NotInheritable Class ComImportAttribute _
	Inherits Attribute

The ComImportAttribute type exposes the following members.

Public methodSupported by Portable Class LibraryComImportAttributeInitializes a new instance of the ComImportAttribute.

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

Public methodSupported by Portable Class LibraryEqualsInfrastructure. Returns a value that indicates whether this instance is equal to a specified object. (Inherited from Attribute.)
Public methodSupported by Portable Class LibraryGetHashCodeReturns the hash code for this instance. (Inherited from Attribute.)
Public methodSupported by Portable Class LibraryGetTypeGets the Type of the current instance. (Inherited from Object.)
Public methodIsDefaultAttributeWhen overridden in a derived class, indicates whether the value of this instance is the default value for the derived class. (Inherited from Attribute.)
Public methodMatchWhen overridden in a derived class, returns a value that indicates whether this instance equals a specified object. (Inherited from Attribute.)
Public methodSupported by Portable Class LibraryToStringReturns a string that represents the current object. (Inherited from Object.)

Explicit interface implemetationPrivate method_Attribute.GetIDsOfNamesMaps a set of names to a corresponding set of dispatch identifiers. (Inherited from Attribute.)
Explicit interface implemetationPrivate method_Attribute.GetTypeInfoRetrieves the type information for an object, which can be used to get the type information for an interface. (Inherited from Attribute.)
Explicit interface implemetationPrivate method_Attribute.GetTypeInfoCountRetrieves the number of type information interfaces that an object provides (either 0 or 1). (Inherited from Attribute.)
Explicit interface implemetationPrivate method_Attribute.InvokeProvides access to properties and methods exposed by an object. (Inherited from Attribute.)

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.


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.

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.

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. 

	'dual,	helpstring("IMyStorage Interface"), 
	'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, SafeArraySubType := VarEnum.VT_VARIANT)> _
                                      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

.NET Framework

Supported in: 4.6, 4.5, 4, 3.5, 3.0, 2.0, 1.1

.NET Framework Client Profile

Supported in: 4, 3.5 SP1

.NET for Windows Phone apps

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

Portable Class Library

Supported in: Portable Class Library

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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