c# - 未找到扩展方法(不是程序集引用问题)

Question

我有以下扩展方法:

public static EntitySet<T> ToEntitySetFromInterface<T, U>(this IList<U> source)
    where T : class, U
{
    var es = new EntitySet<T>();
    IEnumerator<U> ie = source.GetEnumerator();
    while (ie.MoveNext())
    {
        es.Add((T)ie.Current);
    }
    return es;
}

我正在尝试按如下方式使用它:

   List<IItemMovement> p = new List<IItemMovement>();
    EntitySet<ItemMovement> ims = p.ToEntitySetFromInterface<ItemMovement, IItemMovement>();

ItemMovement 实现了 IItemMovement。编译器提示:

'System.Collections.Generic.List' does not contain a definition for 'ToEntitySetFromInterface' and no extension method 'ToEntitySetFromInterface' accepting a first argument of type 'System.Collections.Generic.List' could be found (are you missing a using directive or an assembly reference?)

不，我没有遗漏引用资料。如果我只键入包含它弹出的方法的静态类的名称，扩展方法也是如此。谢谢

Answer 1

这段代码对我有用，它是您代码的直接副本，减去了 ItemMovement 及其接口(interface)，所以这部分可能有问题吗？

public class TestClient
{
    public static void Main(string[] args)
    {
        var p = new List<IItem>();
        p.Add(new Item { Name = "Aaron" });
        p.Add(new Item { Name = "Jeremy" });

        var ims = p.ToEntitySetFromInterface<Item, IItem>();

        foreach (var itm in ims)
        {
            Console.WriteLine(itm);
        }

        Console.ReadKey(true);
    }
}

public class Item : IItem
{
    public string Name { get; set; }
    public override string ToString()
    {
        return Name;
    }
}

public interface IItem
{
}

public static class ExtMethod
{
    public static EntitySet<T> ToEntitySetFromInterface<T, U>(this IList<U> source) where T : class, U
    {
        var es = new EntitySet<T>();
        IEnumerator<U> ie = source.GetEnumerator();
        while (ie.MoveNext())
        {
            es.Add((T)ie.Current);
        }
        return es;
    }
}