CompositionContainer Class

A CompositionContainer object serves two major purposes in an application. First, it keeps track of which parts are available for composition and what their dependencies are, and performs composition whenever the set of available parts changes. Second, it provides the methods by which the application gets instances of composed parts or fills the dependencies of a composable part.

Parts can be made available to the container either directly or through the Catalog property. All the parts discoverable in this ComposablePartCatalog are available to the container to fulfill imports, along with any parts added directly.

The Compose method allows instantiated parts to be added to an existing container. Assuming composition is successful, these parts will have their imports filled with parts retrieved from the container, and their exports will be available to other parts. Imports marked as recomposable will be registered for recomposition.

The SatisfyImportsOnce method allows a part to have its imports filled without being added to the container. If the composition is successful, the part's imports will be filled, but the part's exports will not be available to other parts and no imports will be registered for recomposition.

CompositionContainer objects should always be disposed. When the Dispose method is called, the CompositionContainer object also disposes all the parts that it has created.

A CompositionContainer object that can be accessed from multiple threads must be constructed with the isThreadSafe parameter set to true, using the CompositionContainer constructor. Performance will be slightly slower when isThreadSafe is true, so we recommend that you set this parameter to false in single-threaded scenarios. The default is false.

Caution
A CompositionContainer should never import itself, or a part that has a reference to it. Such a reference could allow an untrusted part to gain access all the parts in the container.

In the following example, a CompositionContainer object is initialized with a catalog and is used to fill the imports of a part. This example uses the Attributed Programming Model.

[Export]
class MyAddin
{
    public String myData { get { return "The data!"; } }
}

class MyProgram
{
    [Import]
    public MyAddin myAddin { get; set; }
}


class Program
{
    static void Main(string[] args)
    {
        AggregateCatalog catalog = new AggregateCatalog();
        catalog.Catalogs.Add(new AssemblyCatalog(typeof(MyAddin).Assembly));
        CompositionContainer _container = new CompositionContainer(catalog);
        MyProgram myProgram = new MyProgram();
        _container.SatisfyImportsOnce(myProgram);
        Console.WriteLine(myProgram.myAddin.myData);
        Console.ReadLine();

        _container.Dispose();
    }
}

.NET Framework

.NET Framework Client Profile

Portable Class Library

Windows 7, Windows Vista SP1 or later, Windows XP SP3, Windows Server 2008 (Server Core not supported), Windows Server 2008 R2 (Server Core supported with SP1 or later), Windows Server 2003 SP2

Reference

Other Resources