Running an Executable and Collecting the Output

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Sometimes in the middle of a .NET application (either C# or VB) you want to run an executable and collect the output.  This post presents a simple function (RunExecutable) that makes it easy to do this.

I write a lot of documents that contain code.  Many of those documents also contain the expected output from the code.  When you have a very large document with many code snippets, it is useful to automate the testing of those snippets.  It gives me a warm and fuzzy feeling to verify that all of the code in my document(s) is validated just before I publish.  I’m going to use RunExecutable in an upcoming post that shows how to extract C# code from an Open XML document, compile it, run it, and validate that the output matches the output in the document.  This is particularly useful to, say, authors writing programming books.

But this code is useful in its own right.  Here is the code to run an executable, and collect the output:

using System;

using System.Text;

using System.IO;

using System.Diagnostics;

class RunResults

{

    public int ExitCode;

    public Exception RunException;

    public StringBuilder Output;

    public StringBuilder Error;

}

class Program

{

    public static RunResults RunExecutable(string executablePath, string arguments,

        string workingDirectory)

    {

        RunResults runResults = new RunResults

        {

            Output = new StringBuilder(),

            Error = new StringBuilder(),

            RunException = null

        };

        try

        {

            if (File.Exists(executablePath))

            {

                using (Process proc = new Process())

                {

                    proc.StartInfo.FileName = executablePath;

                    proc.StartInfo.Arguments = arguments;

                    proc.StartInfo.WorkingDirectory = workingDirectory;

                    proc.StartInfo.UseShellExecute = false;

                    proc.StartInfo.RedirectStandardOutput = true;

                    proc.StartInfo.RedirectStandardError = true;

                    proc.OutputDataReceived +=

                        (o, e) => runResults.Output.Append(e.Data).Append(Environment.NewLine);

                    proc.ErrorDataReceived +=

                        (o, e) => runResults.Error.Append(e.Data).Append(Environment.NewLine);

                    proc.Start();

                    proc.BeginOutputReadLine();

                    proc.BeginErrorReadLine();

                    proc.WaitForExit();

                    runResults.ExitCode = proc.ExitCode;

                }

            }

            else

            {

                throw new ArgumentException("Invalid executable path.", "executablePath");

            }

        }

        catch (Exception e)

        {

            runResults.RunException = e;

        }

        return runResults;

    }

    public static void Main()

    {

        RunResults runResults = RunExecutable("./ConsoleApplication2.exe", "aaa bbb ccc", ".");

        if (runResults.RunException != null)

            Console.WriteLine(runResults.RunException);

        else

        {

            Console.WriteLine("Output");

            Console.WriteLine("======");

            Console.WriteLine(runResults.Output);

            Console.WriteLine("Error");

            Console.WriteLine("=====");

            Console.WriteLine(runResults.Error);

        }

    }

}

After input from Jochan (see below), I've updated the code as shown.  Thanks, Jochan!

Code is attached.