VB Validation

[Dorza]

Ive been trying for hours but can't get what im about to explain to work so ive resorted to asking on here.

My problem is that I want a text box to only accept any one of the following values A, B, C, D. Any other key that is pressed simply isnt entered into the textbox. Since im not all that clued up with VB im not too sure how its done. Any help would be appreciated.

[mike_w]

I did something like this before... I can't be specific about the exact code, since I haven't touched VB in ages, but I can (try and) give you the general gist.

I created a function for when the text box changes. It took the value of the text, and checked it against the values it should be, using an if statement (or a switch/select, whatever it is called). If it wasn't the correct value, you can set textBox.text to a blank value. This probably won't work, but it would be something like this:

function textBox changes                 (Should be pretty obvious what this is suppsed to be)
     if textBox.text = "A" then
          do whatever
     else
          textBox.text = ""
     endif

If it already has a value in, you let the user add a character, and save the current string. You look at the right most character, and if it is a valid character, it replaces the current value, otherwise, it uses the existing value. e.g.

function textBox changes                 (Should be pretty obvious what this is suppsed to be)

     Dim rightChar as string                     (Can't remember the data types)

     rightChar = right(textBox.text,1)

     if rightChar = "A" then
          textBox.text = rightChar
     else
          textBox.text = left(textBox.text,1)
     endif

Hope that helps! If that isn't what you wanted, feel free to shout at me. No doubt there's a far better way of doing it as well.

[TheAnimus]

you using VB6, or VB.net?

in vb.net its much nicer way of doing this.

[RedPutty]

I haven't done vb in years so this might not be exactly right but it works I used it a few times.

you want to use the onkeydown (or could it be onkeypress) event and set the keycode to '' (or is it zero, cant remember) if its not one of your desired ones.

If you only want a single character then make the maxlength 1.


Actually if thats what you want then just use a dropdown, not a textbox!

[Dorza]

Thanks for your input guys. I decided to go back to a dropdown box as i had before. Only reason i changed to a text box was because you could still type things into the text area part of the dropbox before you drop the menu down. How can that be prevented? Locking or disableing the dropbox makes it useless for the user.