PART II in Visual C#.NET

Painting Quick Response Code in Visual C#.NET PART II

Main thread starting Child #1 starting In Child #1, Count In Child #1, Count In Child #1, Count In Child #1, Count In Child #1, Count In Child #1, Count In Child #1, Count In Child #1, Count In Child #1, Count In Child #1, Count Child #1 terminating Main thread ending

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Often in a multithreaded program, you will want the main thread to be the last thread to finish running Technically, a program continues to run until all of its foreground threads have finished Thus, having the main thread finish last is not a requirement It is, however, good practice to follow because it clearly defines your program s endpoint The preceding program tries to ensure that the main thread will finish last by checking the value of Count within Main( ) s do loop, stopping when Count equals 10, and through the use of calls to Sleep( ) However, this is an imperfect approach Later in this chapter, you will see better ways for one thread to wait until another finishes

While the preceding program is perfectly valid, some easy improvements will make it more efficient First, it is possible to have a thread begin execution as soon as it is created In the case of MyThread, this is done by instantiating a Thread object inside MyThread s constructor Second, there is no need for MyThread to store the name of the thread since Thread defines a property called Name that can be used for this purpose Name is defined like this: public string Name { get; set; } Since Name is a read-write property, you can use it to set the name of a thread or to retrieve the thread s name Here is a version of the preceding program that makes these three improvements:

// An alternate way to start a thread using System;

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using SystemThreading; class MyThread { public int Count; public Thread Thrd; public MyThread(string name) { Count = 0; Thrd = new Thread(thisRun); ThrdName = name; // set the name of the thread ThrdStart(); // start the thread } // Entry point of thread void Run() { ConsoleWriteLine(ThrdName + " starting"); do { ThreadSleep(500); ConsoleWriteLine("In " + ThrdName + ", Count is " + Count); Count++; } while(Count < 10); ConsoleWriteLine(ThrdName + " terminating"); } } class MultiThreadImproved { static void Main() { ConsoleWriteLine("Main thread starting"); // First, construct a MyThread object MyThread mt = new MyThread("Child #1"); do { ConsoleWrite(""); ThreadSleep(100); } while (mtCount != 10); ConsoleWriteLine("Main thread ending"); } }

This version produces the same output as before Notice that the thread object is stored in Thrd inside MyThread

The preceding examples have created only one child thread However, your program can spawn as many threads as it needs For example, the following program creates three child threads:

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// Create multiple threads of execution using System; using SystemThreading; class MyThread { public int Count; public Thread Thrd; public MyThread(string name) { Count = 0; Thrd = new Thread(thisRun); ThrdName = name; ThrdStart(); } // Entry point of thread void Run() { ConsoleWriteLine(ThrdName + " starting"); do { ThreadSleep(500); ConsoleWriteLine("In " + ThrdName + ", Count is " + Count); Count++; } while(Count < 10); ConsoleWriteLine(ThrdName + " terminating"); } } class MoreThreads { static void Main() { ConsoleWriteLine("Main thread starting"); // Construct MyThread mt1 MyThread mt2 MyThread mt3 three = new = new = new threads MyThread("Child #1"); MyThread("Child #2"); MyThread("Child #3");

do { ConsoleWrite(""); ThreadSleep(100); } while (mt1Count < 10 || mt2Count < 10 || mt3Count < 10); ConsoleWriteLine("Main thread ending"); } }

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