I too miss discriminated unions in C#.

But even more often, I find myself wishing C# blocks were expressions.

In F#, I could do this:

  let x =
      let z = whatever
      ...
      value

and z is inside a local scope.

So in C#, I want to do:

  var x =
  {
      var z = whatever;
      ...
      value
  };

Maybe it's just me.