Cannot access to property of anonymous type in debug mode (VS2013)

Question

In this sample console app:

class Program
{
    static void Main()
    {
        DoAsyncFoo();
        Console.ReadKey();
    }

    private static async void DoAsyncFoo()
    {
        var task = CollectStatsAsync();
        dynamic foo = await task;
        Console.WriteLine(foo.NumberOfCores);
    }

    private static async Task<dynamic> CollectStatsAsync()
    {
        return CollectStats();
    }

    private static dynamic CollectStats()
    {
        return new { NumberOfCores = 3 };
    }
}

When I put breakpoint to

Console.WriteLine(foo.NumberOfCores)

and evaluate foo.NumberOfCores in debug mode, the output of the error is:

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

Because collectedStats is "Anonymous Object", not "dynamic". However, the function returns dynamic, and I assigned it as dynamic.

Evaluation is successfull for:

((dynamic)foo).NumberOfCores;

By the way, I have realized that if I write the function synchronously, debugger can directly return the result. So it should be about async.

Note: And I have also tried returning Expando Object instead of Anonymous Type from function, the result is same.

Freer

@AlexeiLevenkov it is not in another assembly. – Freer

@CodeCaster no, I already tried returning the expando object and I will attach it to the question. – Freer

@Freer ok. Now it is clear that dynamic does not contain a definition for a property from a project reference is not duplicate due to code being in the same assembly. – Codify

Cannot reproduce. Please create a minimal reproducible example. Do you perform this call over WCF or anything (which does mean the CollectStats implementation is in another assembly)? – Stavanger

@Stavanger I have realized that it only happens in debug mode, then I've edited my question. Here is the sample code ideone.com/CLpHa9, If you put breakpoint to line 19, and evaluate foo.NumberOfCores in VS2013 QuickWatch screen, you will see that. – Freer

The debugger throws your exception, while the Console.WriteLine() does print 3... Weird behavior. Perhaps reduce your question to show the latest code that reproduces it, for brevity? :-) – Stavanger

@Stavanger I've just simplified it :) – Freer

Answer 1

FYI I just tested this in VS 2013 SP4 and it Worked without issue...

Do you have SP4 applied? probably not this, but worth ruling out. As I didn't have any issues.

Code i tired without issue.

public class Program
{
    static void Main()
    {
        DoAsyncFoo();
        Console.ReadKey();
    }

    private static async void DoAsyncFoo()
    {
        var task = CollectStatsAsync();
        dynamic foo = await task;
        Console.WriteLine(foo.NumberOfCores);
    }

    private static async Task<dynamic> CollectStatsAsync()
    {
        return CollectStats();
    }

    private static dynamic CollectStats()
    {
        return new { NumberOfCores = 3 };
    }
}

Filamentous