C# - LINQ 帮助

Question

我需要检查类中是否存在某个属性。 请参阅有问题的 LINQ 查询。 我这辈子都无法让编译器开心。

class Program
{
    static void Main(string[] args)
    {
        ModuleManager m = new ModuleManager();
        IModule module = m.FindModuleForView(typeof(HomeView));
        Console.WriteLine(module.GetType().ToString());
        Console.ReadLine();
    }
}

public class ModuleManager
{
    [ImportMany]
    public IEnumerable<Lazy<IModule>> Modules { get; set; }

    [ImportMany]
    public IEnumerable<Lazy<View>> Views { get; set; }

    public ModuleManager()
    {
        //An aggregate catalog that combines multiple catalogs
        var catalog = new AggregateCatalog();
        //Adds all the parts found in the same assembly as the Program class
        catalog.Catalogs.Add(new AssemblyCatalog(typeof(Program).Assembly));
        //Create the CompositionContainer with the parts in the catalog
        _container = new CompositionContainer(catalog);
        //Fill the imports of this object
        try
        {
            this._container.ComposeParts(this);
        }
        catch (CompositionException compositionException)
        {
            Console.WriteLine(compositionException.ToString());
        }
    }

    public IModule FindModuleForView(Type view)
    {
        //THIS IS THE PROBLEM
        var module = from m in Modules
                     where (
                        from p in m.Value.GetType().GetProperties()
                        where p.GetType().Equals(view)
                        select p
                     )
                     select m;

    }
    public CompositionContainer _container { get; set; }
}

public interface IModule
{
}

[Export]
public class HomeModule : IModule
{
    public HomeModule()
    {
    }

    [Export]
    public HomeView MyHomeView
    {
        get
        {
            return new HomeView();
        }
        set
        {
        }
    }
}


public class HomeView : View
{
}

public class View
{
}

Answer 1

GetProperties()返回 PropertyInfo 的数组对象。您对 p.GetType() 的调用总是会返回 typeof(PropertyInfo) - 而不是您传入的“ View ”类型。

你可能想要这个:

from p in m.Value.GetType().GetProperties() 
where p.PropertyType.Equals(view) 
select p 

编辑

正如 Robert 所指出的，您确定上述查询是否返回任何属性的逻辑也是错误的。一个简单的解决方法是查看子查询是否返回任何内容:

var module = from m in Modules 
             where ( 
                 from p in m.Value.GetType().GetProperties() 
                 where p.PropertyType.Equals(view) 
                 select p 
             ).Any()
             select m

请记住，该查询可能会返回多个模块。您可能希望从结果中返回 .First()。