MEF懒惰导入很多具有Creationpolicy.NonShared [英] MEF Lazy ImportMany with Creationpolicy.NonShared

问题描述

我是MEF的初学者，所以我有一个问题:) 我有以下内容:

i'm a beginner in mef and so i have a question :) i have the following:

[PartCreationPolicy(CreationPolicy.Shared)]
[Export(typeof(SharedExport))]
public class SharedExport : INPCBase
{
    [ImportMany(typeof(INonShared),RequiredCreationPolicy = CreationPolicy.NonShared)]
    private IEnumerable<Lazy<INonShared,Dictionary<string,object>>> fac;

    ...

    public void Open()
    {
        foreach (var lazy in fac)
        {
            this.Muster.Add(lazy.Value);
        }

    }

所有导入的类都标记为非共享.

the imported classes all marked as nonshared.

[PartCreationPolicy(CreationPolicy.NonShared)]
[Export(typeof(INonShared))]
[ExportMetadata("Muster","030")]
public sealed class NonShared1 : INPCBase, INonShared
{
    public NonShared1()
    {
        Debug.WriteLine("ctor NonShared1" + this.GetHashCode().ToString());
    }

    #region Implementation of INonShared

    public string Displayname
    {
        get { return "Muster 030 "+ this.GetHashCode().ToString(); 
        }
    }

    #endregion
}

现在我的问题是:执行Open()时，不应该总是创建一个新的NonShared1实例吗?我总是一样.

now my question: when Open() execute, shouldn't there always a new NonShared1 instance be created? i got always the same.

推荐答案

Matthew关于Shared/NonShared方面是正确的，它仅影响每次导入时给定的实例，每次拉Lazy.Value都不会获得新实例. .如果您想每次获取一个新实例并进行处理，则可以使用ExportFactory.当前，ExportFactory仅存在于MEF的Silverlight版本中，但是如果确实需要此功能，则mef.codeplex.com上有一个示例项目，该功能将该功能添加到了MEF的桌面版本中.

Matthew is correct about the Shared/NonShared aspect only affecting the instance given at each import, you will not get a new instance every time you pull on Lazy.Value. If what you want is to get a new instance each time and dispose it you might look into using ExportFactory. Currently ExportFactory only exists in the Silverlight version of MEF but there is a sample project on mef.codeplex.com that adds the functionality to the desktop version of MEF if you really need this functionality.

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