Catch custom exceptions from an async method

Question

I'm trying to catch a custom exception thrown inside an async method but for some reason it always ends up being caught by the generic exception catch block. See sample code below

class Program
{
    static void Main(string[] args)
    {
        try
        {
            var t = Task.Run(TestAsync);
            t.Wait();
        }
        catch(CustomException)
        {
            throw;
        }
        catch (Exception)
        {
            //handle exception here
        }
    }

    static async Task TestAsync()
    {
        throw new CustomException("custom error message");
    }
}

class CustomException : Exception
{
    public CustomException()
    {
    }

    public CustomException(string message) : base(message)
    {
    }

    public CustomException(string message, Exception innerException) : base(message, innerException)
    {
    }

    protected CustomException(SerializationInfo info, StreamingContext context) : base(info, context)
    {
    }
}

Answer 1

The problem is that Wait throws an AggregateException, not the exception you are trying to catch.

You can use this:

try
{
    var t = Task.Run(TestAsync);
    t.Wait();
}
catch (AggregateException ex) when (ex.InnerException is CustomException)
{
    throw;
}
catch (Exception)
{
    //handle exception here
}