ExportAttribute Class

ExportAttribute Class


Specifies that a type, property, field, or method provides a particular export.

Namespace:   System.ComponentModel.Composition
Assembly:  System.ComponentModel.Composition (in System.ComponentModel.Composition.dll)


[AttributeUsageAttribute(AttributeTargets.Class | AttributeTargets.Method | AttributeTargets.Property | AttributeTargets.Field, 
	AllowMultiple = true, Inherited = false)]
public class ExportAttribute : Attribute


Initializes a new instance of the ExportAttribute class, exporting the type or member marked with this attribute under the default contract name.


Initializes a new instance of the ExportAttribute class, exporting the type or member marked with this attribute under the specified contract name.

System_CAPS_pubmethodExportAttribute(String, Type)

Initializes a new instance of the ExportAttribute class, exporting the specified type under the specified contract name.


Initializes a new instance of the ExportAttribute class, exporting the type or member marked with this attribute under a contract name derived from the specified type.


Gets the contract name that is used to export the type or member marked with this attribute.


Gets the contract type that is exported by the member that this attribute is attached to.


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


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.)


Allows an object to try to free resources and perform other cleanup operations before it is reclaimed by garbage collection.(Inherited from Object.)


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.)


Creates a shallow copy of the current Object.(Inherited from Object.)


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.)

In the Attributed Programming Model, the ExportAttribute declares that a part exports, or provides to the composition container, an object that fulfills a particular contract. During composition, parts with imports that have matching contracts will have those dependencies filled by the exported object.

The ExportAttribute can decorate either an entire class, or a property, field, or method of a class. If the entire class is decorated, an instance of the class is the exported object. If a member of a class is decorated, the exported object will be the value of the decorated member.

Whether or not a contract matches is determined primarily by the contract name and the contract type. For more information, see ImportAttribute.

The following example shows three classes decorated with the ExportAttribute, and three imports that match them.

//Default export infers type and contract name from the
//exported type.  This is the preferred method.
public class MyExport1
    public String data = "Test Data 1.";

public class MyImporter1
    public MyExport1 importedMember { get; set; }

public interface MyInterface


//Specifying the contract type may be important if
//you want to export a type other then the base type,
//such as an interface.
public class MyExport2 : MyInterface
    public String data = "Test Data 2.";

public class MyImporter2
    //The import must match the contract type!
    public MyExport2 importedMember { get; set; }

//Specifying a contract name should only be 
//needed in rare caes. Usually, using metadata
//is a better approach.
[Export("MyContractName", typeof(MyInterface))]
public class MyExport3 : MyInterface
    public String data = "Test Data 3.";

public class MyImporter3
    //Both contract name and type must match!
    [Import("MyContractName", typeof(MyInterface))]
    public MyExport3 importedMember { get; set; }

class Program

    static void Main(string[] args)
        AggregateCatalog catalog = new AggregateCatalog();
        catalog.Catalogs.Add(new AssemblyCatalog(typeof(MyExport1).Assembly));
        CompositionContainer _container = new CompositionContainer(catalog);
        MyImporter1 test1 = new MyImporter1();
        MyImporter2 test2 = new MyImporter2();
        MyImporter3 test3 = new MyImporter3();


.NET Framework
Available since 4.0
Portable Class Library
Supported in: portable .NET platforms
Available since 4.0

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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