Question

[Export]
[Export(typeof(IClass))
public Class : IClass

当我为Class和IClass使用构造函数注入时，我可以期待相同的单例吗？

Answer 1

是的，无论导出的数量如何，每个类型都指定CreationPolicy.Shared，这意味着Export和Export(typeof(IClass))的实际运行时类型结果。您可以通过示例看到这一点：

public interface IMyClass
{
  string Name { get; set; }
}

[Export]
[Export(typeof(IMyClass))]
public class MyClass : IMyClass
{
  private static int count;

  public MyClass()
  {
    count++;
    Name = "Instance " + count;
  }

  public string Name { get; set; }
}

var container = new CompositionContainer(
  new AssemblyCatalog(Assembly.GetExecutingAssembly()));

var instance1 = container.GetExportedValue<MyClass>();
var instance2 = container.GetExportedValue<IMyClass>();

// should be true.
bool referenceEquals = object.ReferenceEquals(instance1, instance2);

// should also be true.
bool nameEquals = instance1.Name == instance2.Name;

在mef中导出两次指向同一个对象

1 个答案: