The IsBackground Property in C#

Encoder QR Code in C# The IsBackground Property

As mentioned earlier, the NET Framework defines two types of threads: foreground and background The only difference between the two is that a process won t end until all of its foreground threads have ended, but background threads are terminated automatically after all foreground threads have stopped By default, a thread is created as a foreground thread It can be changed to a background thread by using the IsBackground property defined by Thread, as shown here: public bool IsBackground { get; set; } To set a thread to background, simply assign IsBackground a true value A value of false indicates a foreground thread

Each thread has a priority setting associated with it A thread s priority determines, in part, how frequently a thread gains access to the CPU In general, low-priority threads gain access to the CPU less often than high-priority threads As a result, within a given period of time, a low-priority thread will often receive less CPU time than a high-priority thread As

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you might expect, how much CPU time a thread receives profoundly affects its execution characteristics and its interaction with other threads currently executing in the system It is important to understand that factors other than a thread s priority can also affect how frequently a thread gains access to the CPU For example, if a high-priority thread is waiting on some resource, perhaps for keyboard input, it will be blocked, and a lowerpriority thread will run Thus, in this situation, a low-priority thread may gain greater access to the CPU than the high-priority thread over a specific period Finally, precisely how task scheduling is implemented by the operating system affects how CPU time is allocated When a child thread is started, it receives a default priority setting You can change a thread s priority through the Priority property, which is a member of Thread This is its general form: public ThreadPriority Priority{ get; set; } ThreadPriority is an enumeration that defines the following five priority settings: ThreadPriorityHighest ThreadPriorityAboveNormal ThreadPriorityNormal ThreadPriorityBelowNormal ThreadPriorityLowest The default priority setting for a thread is ThreadPriorityNormal To understand how priorities affect thread execution, we will use an example that executes two threads, one having a higher priority than the other The threads are created as instances of the MyThread class The Run( ) method contains a loop that counts the number of iterations The loop stops when either the count reaches 1,000,000,000 or the static variable stop is true Initially, stop is set to false The first thread to count to 1,000,000,000 sets stop to true This causes the second thread to terminate with its next time slice Each time through the loop, the string in currentName is checked against the name of the executing thread If they don t match, it means that a task-switch occurred Each time a task-switch happens, the name of the new thread is displayed and currentName is given the name of the new thread This allows you to watch how often each thread has access to the CPU After both threads stop, the number of iterations for each loop is displayed

// Demonstrate thread priorities using System; using SystemThreading; class MyThread { public int Count; public Thread Thrd; static bool stop = false; static string currentName; /* Construct a new thread Notice that this constructor does not actually start the threads running */ public MyThread(string name) { Count = 0;

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Thrd = new Thread(thisRun); ThrdName = name; currentName = name; } // Begin execution of new thread void Run() { ConsoleWriteLine(ThrdName + " starting"); do { Count++; if(currentName != ThrdName) { currentName = ThrdName; ConsoleWriteLine("In " + currentName); } } while(stop == false && Count < 1000000000); stop = true; ConsoleWriteLine(ThrdName + " terminating"); } } class PriorityDemo { static void Main() { MyThread mt1 = new MyThread("High Priority"); MyThread mt2 = new MyThread("Low Priority"); // Set the priorities mt1ThrdPriority = ThreadPriorityAboveNormal; mt2ThrdPriority = ThreadPriorityBelowNormal; // Start the threads mt1ThrdStart(); mt2ThrdStart(); mt1ThrdJoin(); mt2ThrdJoin(); ConsoleWriteLine(); ConsoleWriteLine(mt1ThrdName + " thread counted to " + mt1Count); ConsoleWriteLine(mt2ThrdName + " thread counted to " + mt2Count); } }