Cleanest way to write retry logic?

Question

Occasionally I have a need to retry an operation several times before giving up. My code is like:

int retries = 3;
while(true) {
  try {
    DoSomething();
         


        

Answer 1

I'd implement this:

public static bool Retry(int maxRetries, Func method)
{
    while (maxRetries > 0)
    {
        if (method(maxRetries == 1))
        {
            return true;
        }
        maxRetries--;
    }
    return false;        
}

I wouldn't use exceptions the way they're used in the other examples. It seems to me that if we're expecting the possibility that a method won't succeed, its failure isn't an exception. So the method I'm calling should return true if it succeeded, and false if it failed.

Why is it a Func and not just a Func? So that if I want a method to be able to throw an exception on failure, I have a way of informing it that this is the last try.

So I might use it with code like:

Retry(5, delegate(bool lastIteration)
   {
       // do stuff
       if (!succeeded && lastIteration)
       {
          throw new InvalidOperationException(...)
       }
       return succeeded;
   });

or

if (!Retry(5, delegate(bool lastIteration)
   {
       // do stuff
       return succeeded;
   }))
{
   Console.WriteLine("Well, that didn't work.");
}

If passing a parameter that the method doesn't use proves to be awkward, it's trivial to implement an overload of Retry that just takes a Func as well.