not allow punctuation like comma or periods

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Hi ALL
How could i validate a textbox in vb.net WINDOWS FORM, so that it disallow only two punctuation character that is "," and "."

Posted 27-Feb-11 19:07pm

IndrajitDasgupat

Updated 27-Feb-11 20:10pm

v3

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coolestCoder 28-Feb-11 1:12am

What environment you are talking about ? ASP.Net or Windows Forms ?

IndrajitDasgupat 28-Feb-11 1:29am

Windows Forms

2 solutions

Solution 2

If the only constraint is to disallow punctuation character, validation is not needed. It's better to filter out key presses to ignore unwanted characters in first place, from input. For this purpose:

1) Handle TextBox.KeyPress event;

2) In event handler, get KeyChar from event argument and figure out if this character should be filtered out, in this case, assign event argument's Handled to true.

3) The method char.IsPunctuation(char) helps to classify punctuation characters.

I tested it in code before posting this Answer.

—SA

Posted 27-Feb-11 20:02pm

Sergey Alexandrovich Kryukov

Updated 27-Feb-11 20:03pm

v2

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IndrajitDasgupat 28-Feb-11 2:08am

No it disallow only two punctuation character that is "," and "."

Sergey Alexandrovich Kryukov 28-Feb-11 11:29am

What do you mean "no"? This is the same thing. You just compare KeyChar (which is char) with '.' and ',', instead of using item (3). That's why I explained more general case in (2); because I knew there can be variants of the check. Just do it, I tested and make sure it works correctly.
--SA

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Not Active · Accepted Answer · 2011-02-27T19:16:00

Solution 1

Use a regular expression validator

Posted 27-Feb-11 19:16pm

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Comments

Sergey Alexandrovich Kryukov 28-Feb-11 2:04am

Mark, this is correct answer, my 5, but in this simple case filtering out unwanted characters is much better; please see my answer.
--SA

[no name] 28-Feb-11 7:30am

One or two characters maybe but soon you end up with a long list (hopefully not if statements) to check where a RegEx will check all at once.

Sergey Alexandrovich Kryukov 28-Feb-11 11:32am

Absolutely agree. But if characters can be filtered, they should be filtered, even if validation is ultimately used. Why creating an extra source of user's mistake?

At the same time, if filtering is a bit more complex (such as position or context depended as some tried to do in effort to enforce valid floating-point with exponent and two signs (bad idea!)), then filtering would be too confusing the the user and should not be used.

--SA