演员表错误<dynamic>到 IEnumerable <tuple<string,string> &gt; </tuple<string,string></dynamic>

Question

I am facing an issue while casting an API response type. The API returns List<object> in a particular format code given below

using System;
using System.Collections.Generic;       
        
public class Program
{
    public static void Main()
    {
        dynamic tupleStringList;
        tupleStringList = new List<dynamic>{Tuple.Create("a","b"),Tuple.Create("c","d")}; // this data will come API which I have no control
        IEnumerable<Tuple<string,string>> test = (IEnumerable<Tuple<string,string>>) tupleStringList;// here we need to cast as another internal function which use it as IEnumerable<Tuple<string,string>>
    }
}

The error I am getting is given below

Run-time exception (line 9): Unable to cast object of type 'System.Collections.Generic.List`1[System.Object]' to type 'System.Collections.Generic.IEnumerable`1[System.Tuple`2[System.String,System.String]]' .

Stack Trace:

 [System.InvalidCastException: Unable to cast object of type 'System.Collections.Generic.List`1[System.Object]'`` to type 'System.Collections.Generic.IEnumerable`1[System.Tuple`2[System.String,System.String]]'.] at CallSite.Target(Closure,CallSite,Object ) at System.Dynamic.UpdateDelegates.UpdateAndExecute1[T0,TRet](CallSite site, T0 arg0) at Program.Main():line 9

Answer 1

I suggest tupleStringList.Cast<Tuple<string, string>>() , maybe like:

(IEnumerable<Tuple<string, string>>)(tupleStringList.Cast<Tuple<string, string>>())

(This needs a using System.Linq; directive.)

Ralf has a point in the comments (see Extension method and dynamic object ): If extensions methods are not considered for the binding of a dynamic expression, cast to nongeneric IEnumerable first. For example:

var tupleStringListCast = (IEnumerable)tupleStringList;
var test = tupleStringListCast.Cast<Tuple<string, string>>();

Or call Cast<TResult>() with usual static call syntax:

var test = (IEnumerable<Tuple<string, string>>)(Enumerable.Cast<Tuple<string, string>>(tupleStringList));

---

However, it assumes the pairs are really of type Tuple<,> .