Pitfall of assigning named field tuple to explicit Tuple

[aarondel4]

This was a headscratcher for me. I made the mistake of first declaring my tuple explicitely using types, and then providing field names in the projection, not realizing the field names need to be present in the declaration as well. But across method calls or in linq extensions I couldn't access the field names. I started wondering if tuple field names were something that were maybe lost when passed as parameters, and that it was just some syntax sugar that only worked in local contexts.

Consider an Options -> C# -> Code style configuration defaulted to Suggestion that will suggest changing the declaration to include the field name or to var, if it detects that a name field tuple is being assigned to a tuple without field names.

 IEnumerable<(Peep, Color)> peepsWithColor =
      peeps.Select(f => (
          Peep: f,
          Color: GetRandomColor()
      ));
  var bluePeeps = peepsWithColor.Where(j => j.Color == "blue").ToList(); // Error: ... does not contain a definition for "Color"

[huoyaoyuan]

The type of variable peepsWithColor is explicitly declared, without tuple element name. If you use var instead, the tuple element names will be preserved.

Discussion with C# tooling belongs to dotnet/roslyn repo.

[aarondel4]

The type of variable peepsWithColor is explicitly declared

Yep, I stated "declaring my tuple explicitly"

If you use var instead, the tuple element names will be preserved.

Yep, that's the essence of what I suggested: "suggest changing the declaration to include the field name or to var"