Visual Basic Tutorial - 140 - Keeping Letters Out Of TextBoxes Video Lecture | Mastering Visual Basic - Web Development

hello YouTube say I'm here from
youtube.com slash on live gamer for the
new Boston and in this tutorial I'm just
going to be teaching you guys a little
trick that I used to keep letters
outside of my text boxes so let's say
you only want them to put numbers in
there well here's a simple trick that
you can use for this now if you don't
remember what this is and you haven't
seen the recursion tutorial that doesn't
matter because we're not going to be
working with anything that we've already
made so we'll just go ahead and get some
of this stuff out of the way so now
let's come back to our four Mondavi B
design well select our text box form
let's go over here to the lightning bolt
and we'll double click on the text
changed event so every time they change
the text of this text box what we want
to do is see if they put any letters or
numbers in it so we can just do try and
so what we're going to do is going to
try to convert whatever they have in
there to a double
so we'll do convert dot to double and
then we'll do text box 1 dot text now if
they put an integer in there that does
not have a decimal value this will still
work because doubles are not required to
have decimals in them it just
automatically adds the decimal once you
access them again so let's say we type
in the number 11 and then we print out
the output of this it's going to give us
11 point 0 and it'll still work if you
if that is pretty much an integer so now
if we get an error for this what we want
to do is we just want to tell them
message box not show please only type
numbers
and then after that let's go ahead and
clear that textbox so textbox 1 dot
clear okay so let's go ahead and run
this and you can see that we can type 1
2 we can just keep adding numbers in
here and then if we overflow it should
give us an error but let's say and then
you can see here that if there's nothing
in there that says please only type
numbers so what we can do to this is
enclose this entire try-catch statement
in an if statement so if text box 1 dot
text dot length is greater than 0 so if
there's actually something inside of it
then we'll go ahead and use this and if
not then it's not going to go ahead and
try that try to convert that to a double
because there's nothing there so let's
go ahead and run this again and you can
see that if we type in let's say a it
says please only type numbers and it
clears everything out there and it says
please only type numbers when you type
22:34 and then if we put a character
right there it says please only type
numbers now we also it'll also clear the
text box if we do let's say an @ sign or
something like the tilde key or whatever
that's called under the escape so this
is just an easy way to keep numbers
outside of your text boxes and you can
modify this any way you want to where
you can only allow them to use integers
or shorts or whatever you want and so go
ahead if you have any programs that
you've been wondering how to do that
go ahead and add this in there for the
text change events and you don't really
need much practice with this but once
you understand this right here go ahead
and move on to the next tutorial