C# 7 ValueTuple compile error

Question

I\'m using VS2017 RC and my application targets net framework 4.6.1.

I have two assemblies referencing System.ValueTuple 4.3

MyProject.Services MyProject.Web

Answer 1

If anyone falls in the same trap, to fix this you need to update this package: Microsoft.Net.Compilers to 2.0 (you need to show pre-release)

Answer 2

I just want to add to the other answers.

Remove System.valuetuple from references. Otherwise, it doesn't work and I do not know why. Basically, value tuple is already in 4.7.2 and so if you use visual studio 2019 you're all set.

If you use visual studio 2019 and I did, that's what worked for me. I don't exactly know why. No need for nugget. No need to reference that directly.

Target your project to use .net framework 4.7.2 and remove references to valuetuple.

Answer 3

I think It is because you've not defined fCount, cCount and aCount. Try this

public async Task<(int fCount, int cCount, int aCount)> GetAllStatsAsync()
{
    // Some code...
    //fCount, cCount, aCount are not defined here, so you should define them

    var fCount = 0;
    var cCount= 0;
    var aCount = 0;
    return (fCount , cCount, aCount );

    //Other ways:
    //return (fCount : 0, cCount: 0, aCount : 0);
    //return new (int fCount , int cCount, int aCount ) { fCount = 0, cCount = 0, aCount = 0 };
}

public async Task<HttpResponseMessage> GetInfoAsync()
{
    // Some code...
    var stats = await _myClass.GetAllStatsAsync();

    var vm = new ViewModel
             {
                 FCount = stats.fCount,
                 CCount = stats.cCount,
                 ACount = stats.aCount
             };

     return Request.CreateResponse(HttpStatusCode.OK, vm);
}

Edited with @Swell suggestion

Take a look at this post