Error handling for every iteration with Parallel class

Question

User1904516115 posted

How to handle exception with Parallel class for every iteration? I am using following code but "Handled" message is printing only 5 times

using System;
using System.Threading.Tasks;

namespace ThreadPooling
{
    class Program
    {
        static void Main(string[] args)
        {
            try
            {
                Parallel.For(1, 10, i =>
                {
                    int dividend = 0;
                    int result = i / dividend;
                });
            }
            catch (AggregateException ex)
            {
                ex.Flatten().Handle(p =>
                {
                    Console.WriteLine("Handled");
                    return true;
                });

            }
            Console.ReadLine();
        }
    }
}

Answer 1

User475983607 posted

See the docs

https://docs.microsoft.com/en-us/dotnet/standard/parallel-programming/how-to-handle-exceptions-in-parallel-loops

    class Program
    {
        static void Main(string[] args)
        {
            try
            {
                ProcessDataInParallel();
            }
            catch (AggregateException ae)
            {
                // This is where you can choose which exceptions to handle.
                foreach (var ex in ae.InnerExceptions)
                {
                    if (ex is DivideByZeroException)
                        Console.WriteLine(ex.Message);
                    else
                        throw ex;
                }

            }

            Console.ReadLine();
        }

        private static void ProcessDataInParallel()
        {
            // Use ConcurrentQueue to enable safe enqueueing from multiple threads.
            var exceptions = new ConcurrentQueue<Exception>();

            // Execute the complete loop and capture all exceptions.
            Parallel.For(1, 10, i =>
            {
                try
                {
                    int dividend = 0;
                    int result = i / dividend;
                }
                // Store the exception and continue with the loop.                    
                catch (Exception e) { exceptions.Enqueue(e); }
            });

            // Throw the exceptions here after the loop completes.
            if (exceptions.Count > 0) throw new AggregateException("DivideByZero", exceptions);

        }
    }