为什么带有 ExpandoObject 参数的方法的推导 return 类型总是动态的？

Question

如下代码片段，为什么list的推导类型在VS2017中是动态的？因此，这段代码会产生编译错误。我注意到，如果我将 dynamic 关键字更改为 var，那么一切正常。

如果我想继续使用 dynamic 关键字，该如何解决？

class Program
{
    static void Main(string[] args)
    {
        dynamic d = new ExpandoObject();
        var list = GetList(d); // ===> vs deduced list as dynamic
        var r = list.Select(x => x.Replace("a", "_"));
        var slist = new List<string>();
        var sr = slist.Select(x => x.Replace("a", "_"));
        Console.WriteLine(r.Count());
    }

    static List<string> GetList(ExpandoObject obj)
    {
        List<string> list = new List<string>() { "abc", "def" };
        return list;
    }
}

Answer 1

涉及声明为 dynamic 的参数的操作被推断为 return 动态本身。来自 c# reference:

The result of most dynamic operations is itself dynamic. Operations in which the result is not dynamic include: (1) Conversions from dynamic to another type (2) Constructor calls that include arguments of type dynamic.

如果您想转换回非动态类型，只需按照您想要的方式声明变量即可。这有效：

List<string> list = GetList(d);

...并允许编译其余代码。

为什么带有 ExpandoObject 参数的方法的推导 return 类型总是动态的？

Why the deduced return type of a method with a ExpandoObject parameter is always dynamic?

c#

expandoobject