Introduction

In past developing multithreaded applications in VB was tedious task. Many times spawning new threads actually spawn errors :-) The picture has changed in VB.NET. VB.NET now has simplicity of Java while dealing with threads. We will see a simple example of running your code in a separate thread in following section

Example of Creating Multithreaded Application

Following is a code from threadtest.vb :

imports System
imports System.Threading


public class AClass

	public sub Method1()
	    Dim i as integer
	    For i = 1 to 100
		Console.Writeline
		("inside method1 of AClass object i={0}",i)
	    next
	end sub

	public sub Method2()
	    Dim i as integer
	    For i = 1 to 100
		Console.Writeline
		("inside method2 of AClass object i={0}",i)
	    next
	end sub

end class

public class ThreadTest

	public shared sub Main()
		dim obj as new aclass
		dim th1,th2 as thread

		th1=new Thread
		(new ThreadStart(addressof obj.method1))
		th1.start

		th2=new Thread
		(new ThreadStart(addressof obj.method2))
		th2.start

		dim i as integer
		For i= 1 to 100
		    Console.WriteLine
		    ("Inside the Sub Main i={0} ",i)
		Next
	end sub

end class

Let is dissect the example above :

• We have created our own class called AClass which has two methods Method1 and Method2
• These methods simple have a for loop which prints some message on the console
• We have another class which actually uses our AClass class
• In the Main() method we have created instances of Thread class
• Thread class is available in System.Threading namespace and contains properties and methods to deal with threads
• In the constructor of Thread class we have used the ThreadStart class which is a delegate that points to the method that should be executed when a thread is started.
• To actually run the Methods Start() method of the thread is called
• Compile the application using VBC command line compiler as follows

vbc threadtest.vb /t:exe 

• When you run the exe you will see the output of two methods and main method mixed up   indicating that each method is running concurrently on different threads
• In addition to above methods there are many more methods of thread like

1. Stop() : which stops execution of the thread
2. Suspend() : which suspends execution of thread
3. Resume() : which resumes suspended thread
4. Sleep() : which halts the execution for certain milliseconds