RetryHelper

using System;
using System.Diagnostics;
using System.Threading;

namespace Core {

    public static class RetryHelper {

        /// <summary>
        /// Retries the specified function a certin amount of times before throwing the exception
        /// </summary>
        /// <typeparam name="T">Result of the sucessfull function</typeparam>
        /// <param name="function">Function to excecute</param>
        /// <param name="maxTries">The maximum amount of attempts to exceute the function</param>
        /// <param name="timeoutMilliseconds">Timeout to wait for a function to finish execution</param>
        /// <returns></returns>
        public static T RetryOnFault<T>(Func<T> function,int maxTries,int timeoutMilliseconds = -1) {

            if(function == null)
                throw new ArgumentNullException("function");

            if(Math.Max(maxTries,0) == 0)
                throw new ArgumentOutOfRangeException("maxTries");

            for(int i = 0;i < maxTries;i++) {
                bool timedout = false;
                Exception error = null;
                T result = default(T);

                AutoResetEvent waitEvent = new AutoResetEvent(false);

                //queue up a worker thread
                ThreadPool.QueueUserWorkItem((state) =>
                {
                    try {
                        result = ((Func<T>)state)();
                    }
                    catch(Exception ferror) {
                        error = ferror;
                    }
                    finally {
                        //resume back
                        if(!waitEvent.SafeWaitHandle.IsClosed)
                            waitEvent.Set();
                    }
                },function);

                //wait on the task for the specified time
                timedout = !waitEvent.WaitOne(timeoutMilliseconds);
                waitEvent.Close();
                Debug.Write("Result: " + result);

                //check if task faulted or timed out
                if(error != null || timedout) {
                    if(timedout)
                        error = new TimeoutException();

                    Debug.WriteLine("Attempt " + (i + 1) + " failed: " + error.Message);

                    //check how many errors
                    if(i == maxTries - 1)
                        throw error;
                }
                else
                    return result;
            }

            //should never get here
            return default(T);
        }
    }
}