Predefined type 'System.ValueTuple´2´ is not defined or imported

Question

I've installed Visual Studio 15 Preview 3 and tried to use the new tuple feature

static void Main(string[] args)
{
    var x = DoSomething();
    Console.WriteLine(x.x);
}

static (int x, int y) DoSomething()
{
    return (1, 2);
}

When I compile I get the error:

Predefined type 'System.ValueTuple´2´ is not defined or imported

According to the blog post, this features should be "on" by default.

What did I do wrong?

Answer 1

For .NET 4.6.2 or lower, .NET Core 1.x, and .NET Standard 1.x you need to install the NuGet package System.ValueTuple:

Install-Package "System.ValueTuple"

Or using a package reference in VS 2017:

<PackageReference Include="System.ValueTuple" Version="4.4.0" />

.NET Framework 4.7, .NET Core 2.0, and .NET Standard 2.0 include these types.