A switch expression or case label must be bool (or ...)

Question

Why this swich statement do not work, gives error:

A switch expression or case label must be a bool, char, string, integral, enum, or corresponding nullable type

Code:

 switch (btn.BackColor)
 {
     case Color.Green:
         break;
     case Color.Red:
         break;
     case Color.Gray:
         break;
 }

Answer 1

The error in in itself is self explanatory. it it telling you that switch expression must be ofone of these types: sbyte, byte, short, ushort, int, uint, long, ulong, char, string. or as the C# language specification suggests

exactly one user-defined implicit conversion (§6.4) must exist from the type of the switch expression to one of the following possible governing types: sbyte, byte, short, ushort, int, uint, long, ulong, char, string, or, a nullable type corresponding to one of those types.

And you can see that BackColor is returning your a type here and it is not satisfying any of the above rules, hence the error.

you can do it like this

switch (btn.BackColor.Name)
{
   case "Green":
      break;
   case "Red":
      break;
   case "Gray":
      break;
}

Answer 2

The problem is you can't use a Color in a switch statement. It must be one of the following types, a nullable version of one of the types, or or convertible to one of these types: sbyte, byte, short, ushort, int, uint, long, ulong, char, string

From the C# language spec, 8.7.2:

• Otherwise, exactly one user-defined implicit conversion (§6.4) must exist from the type of the switch expression to one of the following possible governing types: sbyte, byte, short, ushort, int, uint, long, ulong, char, string, or, a nullable type corresponding to one of those types.

In your case, you could work around this by using strings, or just using a set of if/else statements.