Using instr when string is nothing

Question

Hi, I have the following condition

If InStr("a,b,c", stringA) > 0 OrElse (InStr("y,z", stringB) > 0 AndAlso value = 0) Then endif

COndition 1 is false so i check for condition 2 that is "(InStr("y,z", stringB) > 0 AndAlso value = 0) "

What puzzles me is that when stringB is nothing it still falls into the if condition and executes the code.

On first look it would seem that when stringB is nothing condition2 would fail and as a result would not fall into the if condition.

Any explanation why this would happen?

thanks

Answer 1

The InStr() function has an optional overload that starts with the position to start checking (the "start position".) If that is excluded (like as in your example), then it starts searching that the beginning of the string, as you would expect.

When Nothing is passed into the function for stringB, the "start position" is returned. So, one would think that "0" is returned, but in reality you are probably getting "1" back. That is because the InStr function treats the string as a 1-based array of characters instead of a 0-based array of characters. So the "start position" that is returned is 1, not 0; and as we all know 1 is > 0 :) (Source on MSDN)

Answer 2

thanks for the replies. i will start using starting position to get around this problem

contains is part of framework 3.5 only

thanks