Preserving a Variable's Values between Procedure Calls in VB.net
By: Steven Holzner
You've written a function named Counter to keep track of the number of times the user clicks a particular button. Each time through a loop, you call the Counter function to increment the count, but when the program ends, it just displays 0 counts. Why? Let's look at the code:
Module Module1 Sub Main() Dim intLoopIndex As Integer, intValue = 0 For intLoopIndex = 0 To 4 intValue = Counter() Next intLoopIndex System.Console.WriteLine(intValue) End Sub Function Counter() As Integer Dim intCountValue As Integer intCountValue += 1 Return intCountValue End Function End Module
The problem here is that the counter variable, intCountValue, in the Counter function is reinitialized each time the Counter function is called (because a new copy of all the variables local to procedures is allocated each time you call that procedure). The solution is to declare intCountValue as static. This means it will retain its value between calls to the Counter function. Here's the working code:
Module Module1 Sub Main() Dim intLoopIndex As Integer, intValue = 0 For intLoopIndex = 0 To 4 intValue = Counter() Next intLoopIndex System.Console.WriteLine(intValue) End Sub Function Counter() As Integer Static intCountValue As Integer intCountValue += 1 Return intCountValue End Function End Module
Running this code displays a value of 5, as it should.
You can also make intCountValue preserve its value between procedure calls by making it a module-level variable-just declare it outside any procedure. But note that you should restrict the scope of your variables as much as possible (to avoid inadvertent conflicts with variables of the same name), so making this variable a static variable in a procedure is probably a better choice.
You were able to declare a whole function static in VB6, which meant that all the variables in it would be static, but you can't do that in VB .NET.
View Tutorial By: Billyweimb at 2017-05-31 09:44:02
2. Wow cuz this is extremely excellent work! Congrats and keep it up.
View Tutorial By: http://www.votretherapie.us at 2017-05-25 17:49:30
3. thank so much for your site it assists a lot.
View Tutorial By: ________ _________ at 2017-05-25 09:51:13
Comment on this tutorial
- Data Science
- Cloud Computing
- Java Beans
- Mac OS X
- Office 365
- Tech Reviews
Using Resume Next and Resume Line in VB.net
Using On Error GoTo 0 in VB.net
Getting an Exception's Number and Description in VB.net
Raising an Exception Intentionally in VB.net
Exception Filtering in the Catch Block in VB.net
Using Multiple Catch Statements in VB.net
Throwing an Exception in VB.net
Throwing a Custom Exception in VB.net
Changes in Controls from VB6 to VB.net
Unstructured Exception Handling in VB.net
Structured Exception Handling in VB.net