Well, smack me with a wet kipper, I have never really considered the difference between do and do while, since I have always just used a while loop.

Anyway, the difference is, that a do-while will always execute before checking the condtion, whereas a while loop, checks the condition before executing the code block.

Quite a fundamental difference that could prove to be useful, I definetly see a 'gotcha!' interview question from this one if it was ever asked.

class Program
 {
     static void Main()
     {
         int x = 0; 

         // Will always output "Hello World"
         do
         {
             Console.WriteLine("Hello World");
             x++;
         } while (x <= 0); 

         // Will not output anything
         while (x <= 0)
         {
             Console.WriteLine("Hello World");
             x++;
         }
     }
 }