Working with Byval and ByRef keywords

http://msdn.microsoft.com/msdnmag/issues/02/06/Instincts/

It's actually a long story and it's described well in the article above.

First of all Byval mens that your method receives a private copy of the object it's receiving. If you modify it, you are modifying the private copy, not the actual object. ByRef passes an address and not a copy. It's slightly slower since it is an indirection.

If you want to modify a value and pass it back, use ByRef. If you just want to read something and use it as a scratch pad use ByVal. BYVALs are associated with TYPES classes and other reference object are associated byval.

ReneeC at 2007-8-31 >

byval:

private sub DoDisplayMessage(ByVal theMessage as String)

MessageBox.Show(theMessage)

end sub

'Some button1 click event

Me.DoDisplayMessage("Hello! I pressed the button and now I am being called/shown from the DoDisplayMessage, giving this long message to the sub!")

ByRef:

private sub DoChangeMessage(ByRef theMessage as String)

theMessage = "Message modified at: " & DateTime.Now.ToString()

end sub

'some button click event

Dim myMessage as string = "hello"

MessageBox.Show("Before: " & myMessage)

Me.DoChangeMessage(myMessage)

MessageBox.Show("After: " & myMessage)

this article has a sample also

http://msdn2.microsoft.com/en-us/library/chy4288y.aspx

http://msdn2.microsoft.com/en-us/library/dz1z94ha.aspx

ahmedilyas at 2007-8-31 >