返回泛型参数T并返回收益率

我想从加载的dll文件生成一个类型列表(从T类继承)。但当我使用以下代码时,应用程序会冻结/卡住:

static IEnumerable<T> GetAllTypes<T>(string dllName)
{
    Assembly plugin = Assembly.LoadFrom(dllName);
    if (plugin != null)
    {
        Type[] types = plugin.GetTypes();
        foreach (var type in types)
        {
            if (type.IsClass && type.IsSubclassOf(typeof(T)))
            {
                Console.WriteLine(type.Name);
                yield return (T)(Object)type;
            }
        }
    }
    else
        throw new InvalidDataException();
}

然而,如果我不使用收益率回报,一切都会按预期进行,不会发生冻结。有人能解释这种行为吗?

static void GetAllTypes<T>(string dllName)
{
    Assembly plugin = Assembly.LoadFrom(dllName);
    if (plugin != null)
    {
        Type[] types = plugin.GetTypes();
        foreach (var type in types)
        {
            if (type.IsClass && type.IsSubclassOf(typeof(T)))
            {
                Console.WriteLine(type.Name);
                //yield return (T)(Object)type;
            }
        }
    }
    else
        throw new InvalidDataException();
}