How to Catch Exceptions Thrown in Different Threads in C#?

Catching Exceptions Thrown in Different Threads

In multi-threaded programming, it can be challenging to handle exceptions that occur in threads other than the main thread. This issue arises when one method (Method1) spawns a new thread, and that thread executes another method (Method2) that throws an exception. The question is how to capture this exception within Method1.

Solution for .NET 4 and Above

For .NET 4 and later versions, Task class offers a convenient solution. It allows you to get exceptions using the .Exceptions property on the task object. Here are two approaches:

• Handling Exceptions in Task Thread:

  class Program
  {
      static void Main(string[] args)
      {
          Task<int> task = new Task<int>(Test);
          task.ContinueWith(ExceptionHandler, TaskContinuationOptions.OnlyOnFaulted);
          task.Start();
          Console.ReadLine();
      }
  
      static int Test()
      {
          throw new Exception();
      }
  
      static void ExceptionHandler(Task<int> task)
      {
          var exception = task.Exception;
          Console.WriteLine(exception);
      }
  }

• Handling Exceptions in Caller Thread:

  class Program
  {
      static void Main(string[] args)
      {
          Task<int> task = new Task<int>(Test);
          task.Start();
  
          try
          {
              task.Wait();
          }
          catch (AggregateException ex)
          {
              Console.WriteLine(ex);
          }
  
          Console.ReadLine();
      }
  
      static int Test()
      {
          throw new Exception();
      }
  }

In both cases, you get an AggregateException, and the actual exceptions are accessible through ex.InnerExceptions.

Solution for .NET 3.5

For .NET 3.5, you can use the following approaches:

• Handling Exceptions in Child Thread:

  class Program
  {
      static void Main(string[] args)
      {
          Exception exception = null;
          Thread thread = new Thread(() => SafeExecute(() => Test(0, 0), Handler));
          thread.Start();
  
          Console.ReadLine();
      }
  
      private static void Handler(Exception exception)
      {
          Console.WriteLine(exception);
      }
  
      private static void SafeExecute(Action test, Action<Exception> handler)
      {
          try
          {
              test.Invoke();
          }
          catch (Exception ex)
          {
              Handler(ex);
          }
      }
  
      static void Test(int a, int b)
      {
          throw new Exception();
      }
  }

• Handling Exceptions in Caller Thread:

  class Program
  {
      static void Main(string[] args)
      {
          Exception exception = null;
          Thread thread = new Thread(() => SafeExecute(() => Test(0, 0), out exception));
  
          thread.Start();
  
          thread.Join();
  
          Console.WriteLine(exception);
  
          Console.ReadLine();
      }
  
      private static void SafeExecute(Action test, out Exception exception)
      {
          exception = null;
  
          try
          {
              test.Invoke();
          }
          catch (Exception ex)
          {
              exception = ex;
          }
      }
  
      static void Test(int a, int b)
      {
          throw new Exception();
      }
  }

These options provide flexibility in handling exceptions in multi-threaded scenarios, ensuring robust error management in your applications.

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