MEF Programming Guide IV: Using MEF Declaration Export (exports) and imports (imports)

In MEF, you use [System.ComponentModel.Composition.ExportAttribute] to support multiple levels of export part configurations, including classes, fields, properties, and Method-level export parts. By looking at Exportattribute's source code, you know that Exportattribute is defined as Attribute and that it is set up for use.

[System.Diagnostics.CodeAnalysis.SuppressMessage("Microsoft.Performance",　"CA1813:AvoidUnsealedAttributes")]
[AttributeUsage(AttributeTargets.Class　|　AttributeTargets.Field　|　AttributeTargets.Property　|　 AttributeTargets.Method,
　　　　　　　　　　　　　　　　 AllowMultiple　=　true,　Inherited　=　false)]
public　class　ExportAttribute　:　Attribute
{
　　 //......
}

You can use [Exportattribute] to annotate any class object or its internal fields, properties, and methods as a component that can be exported as an exportable part. For example, you need to export an object as a component (class-level export), just add [Exportattribute] to the class, and refer to the MEF components (composable Parts) and the contract (contracts) The basic application, the following is the demo code:

[System.ComponentModel.Composition.Export]
public　class　DBLogger
{
}

For fields, attribute-level exports of the same kind, the sample is annotated with [Exportattribute], and the following code block shows an example of a complete property import and export.

namespace　MEFTraining.ExmprtImport
{
　　　　 public　partial　class　MainPage　:　UserControl
　　　　 {
　　　　　　　　 [Import("Name")]
　　　　　　　　 public　string　BookName　{　get;　set;　}
　　　　　　　　 public　MainPage()
　　　　　　　　 {
　　　　　　　　　　　　 InitializeComponent();
　　　　　　　　　　　　 CompositionInitializer.SatisfyImports(this);
　　　　　　　　　　　　 MessageBox.Show(BookName);
　　　　　　　　 }
　　　　 }
　　　　 public　class　BookService
　　　　 {
　　　　　　　　 [Export("Name")]
　　　　　　　　 public　string　BookName
　　　　　　　　 {
　　　　　　　　　　　　 get　{　return　"《MEF程序设计指南》";　}
　　　　　　　　 }
　　　　 }
}