In VFP we could do this:

do case
 case i < 20
   * Do this
 case i < 40
   * Do that
 otherwise
   * Do that other thing
endcase

In C# it seems you cannot do a logical comparison:

for ( int i = 0; i < 50 ; i++ )
{
switch ( i )
{
  case i < 20:
    do this;
    break;
  default:
    break;
}
}

etc...

What is the easiest way to get the same logic as the former example using VFP in C#?