Programming .NET Components, 2nd Edition

Using .NET Multithreading Services

In addition to the basic multithreading features described at the beginning of this chapter, .NET offers a set of advanced services. Some of these features, such as thread local storage, timers, and the thread pool, are also available in a similar format to Windows developers. Some other features, such as thread-relative static variables, are .NET innovations or are specific aspects of .NET application frameworks. This section briefly describes these .NET multithreading services.

Thread-Relative Static Variables

By default, static variables are visible to all threads in an app domain. This is similar to classic C++ (or Windows), in which static variables are accessible to all threads in the same process. The problem with having all the threads in the app domain able to access the same static variables is the potential for corruption and the resulting need to synchronize access to those variables, which in turn increases the likelihood of deadlocks. Synchronizing access may be a necessary evil, if indeed the static variables need to be shared between multiple threads. However, for cases where such sharing isn’t necessary, .NET supports thread-relative static variables: each thread in the app domain gets its own copy of the static variable. You use the ThreadStatic attribute to mark a static variable as thread-relative:

    public class MyClass
    {
    
       [ThreadStatic]
               static string m_MyString; public static string MyString { set{m_MyString = value;} get{return ...