A sample of Multi Thread programming in Asp.net

Download The Source Code

Please See the clip

Understanding the issue

I was assigned to implement a part of web application that was responsible for calling a java based application. There were some concerns about this part of application as follows:

1. The java based application was supposed to create a file that I had to process that file and show to user

2. A user could run the process from a page but after running he was not able to run it again (since the process took 3 min)

3. When application was running no one else could run application but they were supposed to see that application was run by someone else.

4. Page should be updated every 10 seconds to check whether the process is finished or not

5. When process is finished a file was generated I saved the file output in a temporary table (for simplicity I will save this data in a static variable)

To simulate this let's say we have an application called ExternalApp (a console application) to create a file but creating that file may take 3 min.

class Program { static void Main(string[] args) { if (args.Length == 1) { System.Threading.Thread.Sleep(180000); StreamWriter w = new StreamWriter(args[0],false); for(int i=0;i<10;i++) w.WriteLine(" A Sample Data :"+ i); w.Close(); } } }

Now we should create a web application to call this application by using Multi thread programming.

First I create a library to run the external application in a separate method. We need to check whether the process of running is finished or not. I created two classes one was Director another one was Builder.

Take a look at Director Class:

public class Director { Builder builder; string userName; public static List<string> Result = new List<string>(); public AlgorithemStatus Constract(Builder builder,string user) { this.userName = user; if (HttpContext.Current.Application["athread"] == null) { this.builder = builder; ThreadStart ts = new ThreadStart(RunThread); Thread t = new Thread(ts); t.Start(); HttpContext.Current.Application["athread"] = t; return AlgorithemStatus.AlgorithemRunSuccessful; } else return AlgorithemStatus.AlgorithemWasRunning; } public static bool IsAlgorithemRunning { get { if (HttpContext.Current.Application["athread"] == null) return false; else { Thread t = HttpContext.Current.Application["athread"] as Thread; if (!t.IsAlive) { HttpContext.Current.Application.Remove("athread"); return false; } else return true; } } } private void RunThread() { try { builder.PrepareHistoryFolder(userName); builder.RunExternalAll(); Result = builder.LoadResult(); } catch (Exception ex) { System.IO.StreamWriter w = new System.IO.StreamWriter(System.Configuration.ConfigurationManager.AppSettings["HistoryPath"] + "\\err.log", true); w.WriteLine("Date Time : " + DateTime.Now); w.WriteLine(ex.ToString()); w.Close(); } } }

In This class construct create a new thread and run RunThread method in it. IsAlgorithemRunning Property Check whether the running process has been started. Finally RunThread method calls different method in builder class and retrieve the result.

Check the Builder Class:

using System; using System.Collections.Generic; using System.Text; using System.IO; namespace AlgorithemManagment { public class Builder { private string pathResultExteranlApp; private string pathExternalApp; private StreamWriter statswriter; internal void PrepareHistoryFolder(string userName) { //Check for History folder first string path = System.Configuration.ConfigurationManager.AppSettings["HistoryPath"]; if (!Directory.Exists(path)) Directory.CreateDirectory(path); string foldername = string.Format("{0:d4}_{1:d2}_{2:d2}_{3:d2}_{4:d2}_{5:d2}", DateTime.Now.Year, DateTime.Now.Month, DateTime.Now.Day, DateTime.Now.Hour, DateTime.Now.Minute, DateTime.Now.Second); string HistoryPaht = path + "\\" + foldername; Directory.CreateDirectory(HistoryPaht); pathResultExteranlApp = HistoryPaht + "\\Result.CSV"; pathExternalApp = System.Configuration.ConfigurationManager.AppSettings["ExteranlAppPath"]; string pathstats = HistoryPaht + "\\stats.log"; statswriter = new StreamWriter(pathstats, true); statswriter.WriteLine("User who runned the Algorithem: " + userName); statswriter.WriteLine("Starting DateTime: " + DateTime.Now.ToString()); } internal void RunExternalAll() { System.Diagnostics.Process prc = new System.Diagnostics.Process(); prc.StartInfo.FileName = pathExternalApp; prc.StartInfo.Arguments = pathResultExteranlApp; if (prc.Start()) statswriter.WriteLine("Allocatoin application has just started at " + DateTime.Now.ToString()); prc.WaitForExit(); } internal List<string> LoadResult() { List<string> strs = new List<string>(); StreamReader r = File.OpenText(pathResultExteranlApp); string data = r.ReadLine(); while (data != null) { strs.Add(data); data = r.ReadLine(); } statswriter.WriteLine("Temptable was filled successfully DateTime:" + DateTime.Now.ToString()); statswriter.Close(); return strs; } } }

PrepareHistoryFolder creates a history folder to log and also save the result. RunExternalApp runs the External application and wait until it result is generated. LoadResult read the file generated by external app and process it.

Check the Page code:

protected void Page_Load(object sender, EventArgs e) { if (Director.IsAlgorithemRunning) { PrepareDisableMode(); } else { PrepareEnableMode(); } } private void PrepareEnableMode() { ButtonRunAlgorithm.Enabled = true; imgwait.Visible = false; DataListResult.Visible = true; if (Director.Result.Count > 0) { DataListResult.DataSource = Director.Result; DataListResult.DataBind(); } } private void PrepareDisableMode() { ButtonRunAlgorithm.Enabled = false; imgwait.Visible = true; ClientScript.RegisterStartupScript(typeof(string), "mykey", "<script>RefreshPageinSecond();</script>"); DataListResult.Visible = false; } protected void ButtonRunAlgorithm_Click(object sender, EventArgs e) { PrepareDisableMode(); AlgorithemManagment.Director d = new AlgorithemManagment.Director(); AlgorithemManagment.Builder b = new AlgorithemManagment.Builder(); d.Constract(b,"The User Name"); }

When page is load if algorithm is running we are disabling the button and showing an image indicating we are middle of the process. If algorithm is not running we enable the button and also show the result. When button is clicked we disable button and show the image and also run the algorithm.

Please see the clip to understand the code better.
Please download the source code and also go to web.config file and update the ExteranlAppPath which is the address of ExternalApp exe file and update the HistoryPath which is the address of history folder to log information.

Multi Thread Programming in .NET

What is multi thread programming?

Multi thread programming allows you to do two or more tasks at the same time. As a windows user you have experienced doing two or more tasks together for example while you are listening to music you are using word at the same time you may printing a picture as well. It means that your computer has the ability of doing some tasks simultaneously. Multi thread programming gives you a chance to do this with different parts of the code.

What is process?

Process is a space assigned by CPU allows the code to be run in that space.

What is Thread?

Each process has at least one Thread which is a reference for CPU to run next line in that process

A better definition for Multi threads programming:

Create different thread in current process to run two different parts of the code simultaneously.

Why do we need Multi thread programming?

Each process has at least one thread that run the code called main thread. Sometimes we cannot hang main thread because it is reflecting the hang issue to user. Let me give you an example. Let's say we have a windows application and in part of our code we need to run an external application which may take 1 minute to run. But we cannot spend 1 minute to run this application because the main thread is responsible to render user interface as well so we may create a new thread to do this task for us and leave the main thread to take care of user interface. You see sometimes without multi thread programming our code is not efficient.

How multi thread programming works in .net?

Thanks to .net framework where you can find so many ways to implement multi thread programming. Even you can find this awesome technology in ado.net and UI and... I am going to start from very basic one which is the simple Thread class.

First rule in multi thread programming is that you can run part of your code in another thread as long as your code is defined in a method. It means that if you need to run part of your code in new thread you need to define that code in a method. So a new thread can be run over a method. In .Net there are two classes that help you to do this first is Thread class and second ThreadStart delegate. By ThreadStart you define the address of the method you need to run in a new Thread. By Thread class you start the Thread. Take a look at this code:

ThreadStart ts = new ThreadStart(myfunction); Thread t = new Thread(ts); t.Start();

In above code first myfunction address is assigned to ts delegate then a new object of Thread is created and in constructor the ts is passed to thread object so when Start is called it will start the new thread for ts which is actually myfunction.

I was always asked by students where do we use this how we can use this in a web based application it may not be useful for a web based application. But the reality is that you can use this even in a web based application in next post I show you how! I was assigned a small project that I had to use multi thread programming