Question

Switch statement fallthrough is one of my personal major reasons for loving switch vs. if/else if constructs. An example is in order here:

static string NumberToWords(int number) {     string[] numbers = new string[]          { '', 'one', 'two', 'three', 'four', 'five',            'six', 'seven', 'eight', 'nine' };     string[] tens = new string[]          { '', '', 'twenty', 'thirty', 'forty', 'fifty',            'sixty', 'seventy', 'eighty', 'ninety' };     string[] teens = new string[]         { 'ten', 'eleven', 'twelve', 'thirteen', 'fourteen', 'fifteen',           'sixteen', 'seventeen', 'eighteen', 'nineteen' };      string ans = '';     switch (number.ToString().Length)     {         case 3:             ans += string.Format('{0} hundred and ', numbers[number / 100]);         case 2:             int t = (number / 10) % 10;             if (t == 1)             {                 ans += teens[number % 10];                 break;             }             else if (t > 1)                 ans += string.Format('{0}-', tens[t]);         case 1:             int o = number % 10;             ans += numbers[o];              break;         default:             throw new ArgumentException('number');     }     return ans; } 

The smart people are cringing because the string[]s should be declared outside the function: well, they are, this is just an example.

The compiler fails with the following error:

 Control cannot fall through from one case label ('case 3:') to another Control cannot fall through from one case label ('case 2:') to another 

Why? And is there any way to get this sort of behaviour without having three ifs?

Answer 1

(Copy/paste of an answer I provided elsewhere)

Falling through switch–cases can be achieved by having no code in a case (see case 0), or using the special goto case (see case 1) or goto default (see case 2) forms:

switch (/*...*/) {     case 0: // shares the exact same code as case 1     case 1:         // do something         goto case 2;     case 2:         // do something else         goto default;     default:         // do something entirely different         break; }