Timer in Visual Basic

[sHAHIR]

Introduction:
This tutorial is on how to create a timer in Visual Basic.

Threads:
Te first thing you must know about this tutorial is how to use threads. Threads are essentially processes which run certain parts of your programs code, the main thread handles the design of your form as well as the code of your form, therefore, when you have a lot of long-running code, your UI will freeze. We can get around this by using additional threads.

Design:
For this we simply need one label on a new Windows Form and a numericupdown number box.

We also want a button to begin the timer.

Imports:
For threading, we need to import the threading namespace...

1. Imports System.Threading
   

Button Click:
Once the button is clicked, we first want to create a new thread to run the timer....

1. Private
   
   Sub
   
   Button1_Click(sender As
   
   Object
   
   , e As
   
   EventArgs) Handles Button1.Click
   
2. Dim
   
   trd As
   
   New
   
   thread(AddressOf timing)
   
3. trd.isbackground = True
   
4. trd.start()
   
5. End
   
   Sub
   

we then want to create a variable to hold the current timer time and set the value to the numericupdown value (seconds)...

1. Private
   
   Function
   
   timing()
   
2. Dim
   
   timeing As
   
   Integer
   
   = NumericUpDown1.Value
   
3. End
   
   Function
   

Next we want to loop around through each unit of the numericupdown value, each loop we want to reduce the variable value by one, and re-set the label to the value of the timer, as a string...

1. Private
   
   Function
   
   timing()
   
2. Dim
   
   timeing As
   
   Integer
   
   = NumericUpDown1.Value
   
3. For
   
   i As
   
   Integer
   
   = 0 To
   
   timeing
   
4. Label1.Text = (timeing - i).ToString() + "Seconds..."
   
5. Thread.Sleep(1000)
   
6. Next
   
7. MsgBox("Timer Done"
   
   )
   
8. End
   
   Function
   

Cross Threading:
The final thing we need to do is disable checking for illegal cross thread calls otherwise we will get an error when trying to access the label control from a newly created thread (trd)...

1. Private
   
   Sub
   
   Form1_Load(sender As
   
   Object
   
   , e As
   
   EventArgs) Handles MyBase.Load
   
2. CheckForIllegalCrossThreadCalls = False
   
3. End
   
   Sub