Exception Handling in C# to Python

Question

I've a python script that I'm invoking from C#. Code Provided below. Issue with this process is that if Python script fails I'm not able to understand in C# and display that exception. I'm using C#, MVC, Python. Can you please modify below code and show me how can I catch the exception thrown at the time of Python Script exception?

Process process = new Process();
Stopwatch stopWatch = new Stopwatch();
ProcessStartInfo processStartInfo = new ProcessStartInfo(python);
processStartInfo.UseShellExecute = false;
processStartInfo.RedirectStandardOutput = true;

try
{
      process.StartInfo = processStartInfo;
      stopWatch.Start();
      //Start the process
      process.Start();

      // Read the standard output of the app we called.  
      // in order to avoid deadlock we will read output first 
      // and then wait for process terminate: 
      StreamReader myStreamReader = process.StandardOutput;
      string myString = myStreamReader.ReadLine();

      // wait exit signal from the app we called and then close it. 
      process.WaitForExit();
      process.Close();

      stopWatch.Stop();
      TimeSpan ts = stopWatch.Elapsed;

      Session["Message"] = "Success";
     }
     catch (InvalidOperationException ex)
     {
      throw new System.InvalidOperationException("Bulk Upload Failed. Please contact administrator for further details." + ex.StackTrace);
      Session["Message"] = "Failed";
     }

Add this line processStartInfo.RedirectStandardError = true; and change tis line : StreamReader myStreamReader = process.StandardOutput + process.StandardError; to read the error. — t.m.adam
– t.m.adam, Commented Apr 4, 2017 at 17:44
StreamReader myStreamReader = process.StandardOutput + process.StandardError; like is throwing a compilation Error. Thanks. — Partha Mitra
– Partha Mitra, Commented Apr 4, 2017 at 18:17
Hey Adam - Your answer was pretty close. I modified the code and got the entire exception stack from StandardError. I've provided the working version of the code below as answer. Thanks for the hints. - Thanks. — Partha Mitra
– Partha Mitra, Commented Apr 5, 2017 at 14:57

Partha Mitra · Accepted Answer · 2017-04-05 14:55:04Z

1

Here is the working code.. To get the error or any exception in Python to C# RedirectStandardError property true and next get the Standard Error. Working version of the code is provided below -

process.StartInfo = processStartInfo;
                        processStartInfo.RedirectStandardError = true;

                        stopWatch.Start();
                        //Start the process
                        process.Start();

                        string standardError = process.StandardError.ReadToEnd();

                        // wait exit signal from the app we called and then close it. 
                        process.WaitForExit();
                        process.Close();

                        stopWatch.Stop();
                        TimeSpan ts = stopWatch.Elapsed;

answered Apr 5, 2017 at 14:55

Partha Mitra

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Comments

Sudhakar Tillapudi · Accepted Answer · 2017-04-04 17:49:07Z

0

You can subscribe for ErrorDataReceived event and read the error message.

process.ErrorDataReceived+=process_ErrorDataReceived;

and here is your event handler

void process_ErrorDataReceived(object sender, DataReceivedEventArgs e)
{
    Console.WriteLine(e.Data);
}

edited Apr 4, 2017 at 17:49

answered Apr 4, 2017 at 17:41

Sudhakar Tillapudi

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1 Comment

Partha Mitra Over a year ago

Thank you. ErrorDataReceived comes as null. Unfortunately code is not working as expected. Please let me know if you find any other option.

den.run.ai · Accepted Answer · 2017-04-05 19:57:51Z

0

You can get exceptions passed from Python to C# when embedding CPython in C# with pythonnet:

https://github.com/pythonnet/pythonnet/blob/master/README.md

answered Apr 5, 2017 at 19:57

den.run.ai

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1 Comment

Partha Mitra Over a year ago

Thanks. I've found already found a solution. I posted working code below. Thank you again for your help.

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