Regex Expressions

Question

Hi,
I am working on windows applications
I am using Regex Expressions, I can write regex expression for only digits but my requirement is first to letters are "CH" after my textbox has to accept only digits

Ex: CH4324324
CH11111
CH789798......

In this scenario I dont want to change value CH as prefix of that box

user has to change only after this prefix so any one can tel me regex expression.
problem 2:
I have written to handle unwanted data in keypress events like following way

Regex regex = new Regex((sender as RadMaskedEditBoxElement).Mask);
if (!regex.IsMatch(e.KeyChar.ToString()))
e.Handled = true;
{
return;
}

But its working for only when I press key from keyboard but its not working for copy-paste and cut-paste and paste by using mouse but I want to handle unwanted data for paste
How to do this ?

Any one can tel me reply for above two questions....

Vulpes · Answer

With regard to the first problem, the regular expression you'll need is: string regExp = @"^CH\d+$";

raja ramesh · Answer

Thank you vulpes

Vulpes · Answer

A regular expression can only validate the string as it currently stands. So, if no vowels have been entered so far, it will fail. This is something that you can only really validate properly after the string has been fully entered by the user. However, one thing that might work is not to validate for the vowel until at least 4 characters have been entered. Off the top of my head, I can't think of any words in English which don't have a vowel in the first four characters though there are some which don't have any in the first three such as 'through' , 'street' and 'chronic'.

raja ramesh · Answer

Thank you vulpes Your expression are very useful to me but this is failed in keypress event . Regex regex = new Regex((sender as RadMaskedEditBoxElement).Mask); if (!regex.IsMatch(e.KeyChar.ToString())) { e.Handled = true; return; } if (TextLength> 0) { if (TextLength { newText = radMaskedEditBoxText + e.KeyChar.ToString(); } else if(...) ... if (!regex.IsMatch(newText )) { e.Handled = true; return; } } (This is failed because I think in that expression contains vowels condition). Is there any chance to handle unwated keys in keypress event by using this expression ?

Vulpes · Answer

If by non-mandatory, you mean it could be blank or, if it's not blank, it must contain a vowel, then you could use this: string regExp = @"^(|(?=.*(a|e|i|o|u))[a-z]+)$"; To combine the expression that disallows 3 or more consecutive identical letters with the above but allow commas as well would be: string regExp = @"^(|(?!.*(?'letter'[a-z])\k'letter'{2,})(?=.*(a|e|i|o|u))[a-z,]+)$"; The mandatory version of that would be: string regExp = @"^(?!.*(?'letter'[a-z])\k'letter'{2,})(?=.*(a|e|i|o|u))[a-z,]+$";

raja ramesh · Answer

Thanks for reply Vulpes, Your expression is useful to me but I have some mandatory fields and some non mandatory fields so your expression is suitable for only mandatory fields. how to do for non madatory filds ? 2)I have writen expression to handle for morethan 3 characters are same sequently as following @"^(?!.*(?'letter'[a-z])\k'letter'{2,})[a-z,]+$" Can you write expression for combination of this expression and my previous case(aeiou). Thanks for you advance...

Vulpes · Answer

If only letters are permitted in the name and at least one needs to be a vowel, then this should work: string regExp = @"^(?=.*(a|e|i|o|u))[a-z]+$";

raja ramesh · Answer

Thank you Can you tel me regex expression for name should contain vowels(aeiou). ex: ram---true gdfg----false jkdkj---false asoka----true

Dorababu Meka · Answer

You can just disable the context menu when u right click inside the text box by placing this textBox1.ContextMenu = new ContextMenu(); You can also block the user to copy cut and paste the text using the following code private const Keys CopyKeys = Keys.Control | Keys.C; private const Keys PasteKeys = Keys.Control | Keys.V; private const Keys CutKeys = Keys.Control | Keys.X; protected override bool ProcessCmdKey(ref Message msg, Keys keyData) { if ((keyData == CopyKeys) || (keyData == PasteKeys) || (keyData == CutKeys)) { return true; } else { return base.ProcessCmdKey(ref msg, keyData); } }