Question

Is it possible to have a switch in a lambda expression? If not, why? Resharper displays it as an error.

Answer 1

You can in a statement block lambda:

Action<int> action = x =>
{
  switch(x)
  {
    case 0: Console.WriteLine("0"); break;
    default: Console.WriteLine("Not 0"); break;
  }
};

But you can’t do it in a “single expression lambda”, so this is invalid:

// This won't work
Expression<Func<int, int>> action = x =>
  switch(x)
  {
    case 0: return 0;
    default: return x + 1;
  };

This means you can’t use switch in an expression tree (at least as generated by the C# compiler; I believe .NET 4.0 at least has support for it in the libraries).