Understanding Threading in .NET Framework using VB.NET

t1.Start()

Detailed example is as below

Imports System
Imports System.Threading
Namespace Programming_CSharp
Class Tester
Shared Sub Main()
' make an instance of this class
Dim t As New Tester
' run outside static Main
t.DoTest()
End Sub 'Main
Public Sub DoTest()
' create a thread for the Incrementer
' pass in a ThreadStart delegate
' with the address of Incrementer
Dim t1 As New Thread(AddressOf Incrementer)
' create a thread for the Decrementer
' pass in a ThreadStart delegate
' with the address of Decrementer
Dim t2 As New Thread(AddressOf Decrementer)
' start the threads
t1.Start()
t2.Start()
End Sub 'DoTest
' demo function, counts up to 1K
Public Sub Incrementer()
Dim i As Integer
For i = 0 To 999
Console.WriteLine("Incrementer: {0}", i)
Next i
End Sub 'Incrementer
' demo function, counts down from 1k
Public Sub Decrementer()
Dim i As Integer
For i = 1000 To 0 Step -1
Console.WriteLine("Decrementer: {0}", i)
Next i
End Sub 'Decrementer
End Class 'Tester
End Namespace 'Programming_CSharp

Output:

Incrementer: 102
Incrementer: 103
Incrementer: 104
Incrementer: 105
Incrementer: 106
Decrementer: 1000
Decrementer: 999
Decrementer: 998
Decrementer: 997

Joining Threads

Once thread starts running and in a situation when we need to tell thread to stop processing and wait until a second thread to complete the processing we need to join the 1st thread to the 2nd thread. Use following for the same. This will join the second thread to the 1st.

Example:

t2.Join( )

Suspending Thread

In a situation we some time needs to suspend running thread.

Example:

t2.Sleep(<No of Seconds>)

Killing Thread

Threads has to die after the execution of the process in normal situations, occasionally it is required for the programmer to kill a thread. Threads can be killed using the following.

Example:

t2.Abort()

Advanced Threading

Synchronization

Recollect the discussion we had before in some situations we need to synchronize the running threads, so we can modify the running thread and its resources.

Imports System
Imports System.Threading
Namespace Programming_CSharp
Class Tester1
Private counter As Integer = 0
Shared Sub Main()
' make an instance of this class
Dim t As New Tester
' run outside static Main
t.DoTest()
End Sub 'Main
Public Sub DoTest()
Dim t1 As New Thread(AddressOf Incrementer)
t1.IsBackground = True
t1.Name = "ThreadOne"
t1.Start()
Console.WriteLine("Started thread {0}", t1.Name)
Dim t2 As New Thread(AddressOf Incrementer)
t2.IsBackground = True
t2.Name = "ThreadTwo"
t2.Start()
Console.WriteLine("Started thread {0}", t2.Name)
t1.Join()
t2.Join()
' after all threads end, print a message
Console.WriteLine("All my threads are done.")
End Sub 'DoTest
' demo function, counts up to 1K
Public Sub Incrementer()
Try
While counter < 1000
Dim temp As Integer = counter
temp += 1 ' increment
' simulate some work in this method
Thread.Sleep(1)
' assign the decremented value
' and display the results
counter = temp
Console.WriteLine("Thread {0}. Incrementer: {1}", Thread.CurrentThread.Name, counter)
End While
Catch
Finally
Console.WriteLine("Thread {0} Exiting. ", Thread.CurrentThread.Name)
End Try
End Sub 'Incrementer
End Class 'Tester
End Namespace 'Programming_CSharp

Output:

Started thread ThreadOne
Started thread ThreadTwo
Thread ThreadOne. Incrementer: 1
Thread ThreadOne. Incrementer: 2
Thread ThreadOne. Incrementer: 3
Thread ThreadTwo. Incrementer: 3
Thread ThreadTwo. Incrementer: 4
Thread ThreadOne. Incrementer: 4
Thread ThreadTwo. Incrementer: 5
Thread ThreadOne. Incrementer: 5
Thread ThreadTwo. Incrementer: 6
Thread ThreadOne. Incrementer: 6

Using Interlock

MS CLR provides synchronization tools and mechanisms. This will allow programmers to place locking over running threads.

VB provides a special class called interlocked just for the reason of locking. This consists of two methods Increment and Decrement.

Example: