MEF Programming Guide VIII: Part lifecycle (Parts lifetimeime) Hosting

Each of the exported parts that can be dynamically assembled in the MEF is lifecycle-the lifecycle is generally not managed without special requirements, and in fact MEF has the default lifecycle management for each component, and the MEF's lifecycle is divided into three categories: any, Shared and nonshared are defined in the System.ComponentModel.Composition.CreationPolicy enumeration object.

namespace　System.ComponentModel.Composition
{
　　　　 public　enum　CreationPolicy
　　　　 {
　　　　　　　　　 Any　=　0,
　　　　　　　　　 Shared　=　1,
　　　　　　　　　 NonShared　=　2,
　　　　 }
}

Any representation that can be shared or unshared, where instances of a part are automatically controlled according to different request requirements using the MEF container; shared represents a shared part, and a plug-in part that is of the same type can be used in multiple MEF combination containers, followed by the nonshared type, which indicates that the part instance is not shared. A new object instance is created whenever a new request is made. In MEF, the life cycle configuration of a part is implemented through the Partcreationpolicyattribute attribute.

public　interface　IBookService
{
　　　　 string　GetBookName();
}
[PartCreationPolicy(CreationPolicy.Any)]
[Export(typeof(IBookService))]
public　class　MEFBookService　:　IBookService
{
　　　　 public　string　GetBookName()
　　　　 {
　　　　　　　　 return　"《MEF程序设计指南》";
　　　　 }
}
[PartCreationPolicy(CreationPolicy.NonShared)]
[Export(typeof(IBookService))]
public　class　ASPNETBookService　:　IBookService
{
　　　　 public　string　GetBookName()
　　　　 {
　　　　　　　　 return　"《ASP.NET项目案例》";
　　　　 }
}
[PartCreationPolicy(CreationPolicy.Shared)]
[Export(typeof(IBookService))]
public　class　SLBookService　:　IBookService
{
　　　　 public　string　GetBookName()
　　　　 {
　　　　　　　　 return　"《Silverlight高级编程》";
　　　　 }
}