Question

我与MEF合作很长一段时间，偶尔它会让我发疯。不知道它需要什么。

我有两个我们感兴趣的文件：

我的EXE有两个班级：

JobFactory：IJobFactory和SaferWatchProcessor：IJob

具有这些接口定义的Quartz.net DLL

创建容器：

var aggregateCatalog = new AggregateCatalog(
                new DirectoryCatalog(".", "*.dll"),
                new DirectoryCatalog(".", "*.exe"));

            Bootstrapper.CompositionContainer = new CompositionContainer(aggregateCatalog, true);

目录现在有JobFactory但没有SaferWatchProcessor。为什么呢？

enter image description here

这是课程：

[Export(typeof(IJob))]
public class SaferWatchProcessor : IJob
{
    public void Execute(IJobExecutionContext context)
    {
        Debug.WriteLine("SaferWatchProcessor.Execute");
    }
}

SaferWatchProcessor没有任何东西，只有一种方法。有导出属性。

[Export(typeof(IJobFactory))]
    public class JobFactory : IJobFactory
    {
        [ImportMany(typeof(IJob))]
        public List<IJob> Jobs { get; private set; }

        public virtual IJob NewJob(TriggerFiredBundle bundle, IScheduler scheduler)
        {
            IJobDetail jobDetail = bundle.JobDetail;
            Type jobType = jobDetail.JobType;
            try
            {
                Debug.WriteLine("IDATT.WindowsService.JobFactory - creating job instance");
                return this.Jobs.First();
            }
            catch (Exception e)
            {
                var se = new SchedulerException(string.Format(CultureInfo.InvariantCulture, "Problem instantiating class '{0}'", jobDetail.JobType.FullName), e);
                throw se;
            }
        }

        public virtual void ReturnJob(IJob job)
        {
        }
    }

JobFactory有ImportMany（不会失败，但有0项）

我尝试将其设置为单个导入，并且出现以下错误：

System.ComponentModel.Composition Warning: 1 : The ComposablePartDefinition 'IDATT.WindowsService.JobFactory' has been rejected. The composition remains unchanged. The changes were rejected because of the following error(s): The composition produced a single composition error. The root cause is provided below. Review the CompositionException.Errors property for more detailed information.

    1) No exports were found that match the constraint: 
        ContractName    Quartz.IJob
        RequiredTypeIdentity    Quartz.IJob

    Resulting in: Cannot set import 'IDATT.WindowsService.JobFactory.Jobs (ContractName="Quartz.IJob")' on part 'IDATT.WindowsService.JobFactory'.
    Element: IDATT.WindowsService.JobFactory.Jobs (ContractName="Quartz.IJob") -->  IDATT.WindowsService.JobFactory -->  DirectoryCatalog (Path=".")

    A first chance exception of type 'System.InvalidOperationException' occurred in IDATT.WindowsService.exe

似乎没有错，但为什么它不想导入IJob？

编辑：

我删除了所有IJob定义并使用普通导出/导入并为MEF添加了调试。仍有问题，这里是错误：

[Part] IDATT.WindowsService.JobFactory from: DirectoryCatalog (Path="C:\CodeWorkspace\IdattLC\ClientServerCode\IDATT.WindowsService\bin\Debug\")
  [Primary Rejection]
  [Export] IDATT.WindowsService.JobFactory (ContractName="Quartz.Spi.IJobFactory")
  [Import] IDATT.WindowsService.JobFactory.SaferWatchProcessor (ContractName="IDATT.WindowsService.Jobs.SaferWatchProcessor")
    [Exception] System.ComponentModel.Composition.ImportCardinalityMismatchException: No exports were found that match the constraint: 
    ContractName    IDATT.WindowsService.Jobs.SaferWatchProcessor
    RequiredTypeIdentity    IDATT.WindowsService.Jobs.SaferWatchProcessor
   at System.ComponentModel.Composition.Hosting.ExportProvider.GetExports(ImportDefinition definition, AtomicComposition atomicComposition)
   at System.ComponentModel.Composition.Hosting.ExportProvider.GetExports(ImportDefinition definition)
   at Microsoft.ComponentModel.Composition.Diagnostics.CompositionInfo.AnalyzeImportDefinition(ExportProvider host, IEnumerable`1 availableParts, ImportDefinition id)

Answer 1

好的，我认真思考。我认为发布我的发现会很有用。

我发生了什么，我从NuGet安装了MEF 2，新的轻量级MEF for 4.5和Windows商店。

我现有的所有库都是使用常规的旧MEF构建的 using System.ComponentModel.Composition对于这个有问题的导入，ReSharper建议使用几个名称空间，并使用import using System.Composition作为导出属性

不确定MEF 2有什么用处，但它不适用于常规MEF的现有库/出口，所以要小心！

Answer 2

这是一个快速检查清单：

确保将SaferWatchProcessor类型的程序集物理复制到目录文件夹
确保相应的程序集是新的并且在目录文件夹中具有正确的时间戳
确保SaferWatchProcessor类型确实导出Quartz.IJob。当人们尝试导出由Visual Studio创建的空接口而不是引用真实的

使用特定接口时MEF组合导入问题

2 个答案: