Question

One of my method (Method1) spawns a new thread.
That thread execute a method (Method2) and during exectution an exception is thrown.
I need to get that exception information on the calling method (Method1)

Is there someway I can catch this exception in Method1 that is thrown in Method2?

Answer 1

In .NET 4 and above, you can use Task<T> class instead of creating new thread. Then you can get exceptions using .Exceptions property on your task object.
There are 2 ways to do it:

1. In a separate method: // You process exception in some task’s 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);
       }
   }
   

2. In the same method: // You process exception in the caller’s 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();
       }
   }
   

Note that the exception which you get is AggregateException. All real exceptions are availible through ex.InnerExceptions property.

In .NET 3.5 you can use the following code:

1. // You process exception in the child’s 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();
       }
   }
   

2. Or // You process exception in the caller’s 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();
       }
   }