uuh I dunno how to do this but I sure do hope it's possible in C#

I have a switch and I want code execution to fall from one case to another if a certain condition isn't met

Code:
switch (something)
{
    case 1:
         if (val==true)
         {
             //do stuff;
             break;
         }
         else
          {
               // go on to other case statements.... but how? it won't compile without break;
          }
    case 2:
    case 3:

}