Evaluate Expressions in Switch Statements in C#

Question

I have to implement the following in a switch statement:

switch(num)
{
  case 4:
    // some code ;
    break;
  case 3:
    // some code ;
    break;
  case 0:
    // some code ;
    break;
  case < 0:
    // some code ;
    break;
}

Is it possible to have the switch statement evaluate case < 0? If not, how could I do that?

Answer 1

You can't - switch/case is only for individual values. If you want to specify conditions, you need an "if":

if (num < 0)
{
    ...
}
else
{
    switch(num)
    {
        case 0: // Code
        case 1: // Code
        case 2: // Code
        ...
    }
}

Answer 2

You will have to use if, wether you want or not. Switch is only capable of comparing your value to constant values.

Answer 3

If your num can't be less than zero:

public int GetSwitch(int num) { return num < 0 ? -1 : num; }
switch(GetSwitch(num))
{
case 4: // some code ; break;
case 3:// some code ; break;
case 0: // some code ; break;
case -1 :// some code ; break;
}

If it can, use some other "non-existent" number such as int.MinValue.

Answer 4

The only way I could think of (and I really don't recommand it), would be as follows:

int someValue;

switch (Math.Max(someValue, -1))
{
    case -1:
        // will be executed for everything lower than zero.
        break;

    case 0:
       // will be executed for value 0.
       break;

    case 1:
       // will be executed for value 1.
       break;

    default:
       // will be executed for anything else.
       break;
}

Answer 5

You could do something like this at the end of your switch statement:

default:
    if(num < 0)
    {
        ... // Code
    }
    break;

Answer 6

The other way around would be possible also (relating to Jon Skeet's answer):

switch(num)
{
  case a:
      break;
  default:
      if( num < 0 )
      {}
   break;
}

Answer 7

You cannot use comparisons in switches like you could in VB, you have 2 options here, replace the value you switch on with a known value and use that or - if you mean all other cases - you can use the default clause:

switch(num)
{
  case 4:
    // some code ;
    break;
  case 3:
    // some code ;
    break;
  case 0:
    // some code ;
    break;
  default:
    // some code ;
    break;
}

Note that this does not exactly like you asked for: any values other than 0,3,4 will end up in the deafult: clause.