Starting a Process (application) sending arguments and reading the Output/Error

Any application like notepad or calculator or user applications (console or windows) can be invoked using “Process” class which falls in “System.Diagnostics” package or namespace.

Below code demonstrates, creating a console application “Divide2Numbers” which accepts 2 arguments and writes the division of the given numbers to console.

using System;

using System.Collections.Generic;

using System.Linq;

using System.Text;

namespace Divide2Numbers

{

    class Program

    {

        static void Main(string[] args)

        {

            //getting the input arguments and writing the result of the division

            double a = double.Parse(args[0]);

            double b = double.Parse(args[1]);

            Console.Write("Division of {0} and {1} is {2}", a, b, (a / b));

        }

    }

}

A windows application is created which has 2 textboxes to enter value for “a” and “b”.

User will enter the values and click on “Divide” button.

The .exe created from above console application is copied to the current windows application directory.

In the button “Divide” click event, application will create a process object which will invoke the above console application exe and sends the a, b arguments.

private void Divide_Click(object sender, EventArgs e)

        {

            try

            {

                //new process

                System.Diagnostics.Process p1 = new System.Diagnostics.Process();

                //sending the arguments (a,b) to divide application

                p1.StartInfo.Arguments = txtA.Text + " " + txtB.Text;

                //CreateNoWindow=false, to not open the process ui.

                p1.StartInfo.CreateNoWindow = false;

                //The application file path

                p1.StartInfo.FileName = Application.StartupPath + "/Divide2Numbers.exe";

                //UseShellExecute must be set to false, to redirect IO streams

                p1.StartInfo.UseShellExecute = false;

                //to redirect the error that occurs in the process

                p1.StartInfo.RedirectStandardError = true;

                //to redirect the output from the process

                p1.StartInfo.RedirectStandardOutput = true;

                //to start the process

                p1.Start();

                //reading the error and output from stream

                StreamReader oR = p1.StandardOutput;

                StreamReader eR = p1.StandardError;

                string strError = eR.ReadToEnd();

                string strOutput = oR.ReadToEnd();

                //displaying the error or result

                lblResult.Text = (strOutput.Trim().Length > 0) ? "Result : " + strOutput : "Error : " + strError;

            }

            catch (Exception exp)

            {

                MessageBox.Show("Error : " + exp.Message);

            }

        }

When user enters the value of a, b and click on “Divide” the application gets the result from console application through output stream.

Incase of Error, applications gets the error via Error Stream reader.