Regex Expressions

jayaram

^[0-9]*$ -I used this is for accept digits and

^[A-Za-z]*$ this is for alphabets

^[A-Za-z0-9]*$ I used this expression for accept digits and alphabets and
these are work correctly
and
If I entered special characters(!@$@#%$^&%&) I am getting an error message
but I can enter these characters

But my requirement is I dont want to accept special characters from my keyboard to my textbox

EX:numeric textbox can accept only digits other characters can not be accept

Thanks

15 Replies

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Vulpes15y ago
The maximum length of the string that can be matched is implicit in the regular expression.

For example, if we take this:

string regExp = @"^\d+$";

then it will match a string which contains any number of consecutive digits, as long as there's at least one and no other character appears.

To match a minimum of 3 and a maximum of 12 digits, you'd need to change it to:

string regExp = @"^\d{3,12}$";
jayaram15y ago
Thanks for you vulpes
In my regeex expression I set maxlength(ex:\d{4}) but
maxlength is not working based on expression.

In this case maskedEditbox control length is taken by Maxlength property of RadmaskedEditbox.

how can i set maxlength for maskedEditbox by using regex expression
Vulpes15y ago
As I said earlier, I'm not familiar with the Telerik RadMaskedEditBoxElement control and so I don't know whether it has the same properties and events as the .NET MaskedTextBox or not.

However, if you've added a ContextMenu to it - which comes up when the mouse is right clicked - and you've added a 'Paste' MenuItem to the ContextMenu, then I'd have thought that you'd need to handle the latter's Click event on something like the following lines:

private void menuItemPaste_Click(object sender, EventArgs e)
{
MenuItem mi = (MenuItem)sender;
ContextMenu cm = mi.GetContextMenu();
RadMaskedEditBoxElement rmebe = (RadMaskedEditBoxElement)cm.SourceControl;
Regex regex = new Regex(rmebe.Mask);
if (regex.IsMatch(Clipboard.GetText())) rmebe.Paste();
}
jayaram15y ago
Thank you vulpes for all your responses,
Once you sent code for handle unwanted data to paste in textbox this validate after leave from textbox but I want to ignore data from my textbox , I modify for this requirement e.SuppressKeyPress = !(regex.IsMatch(Clipboard.GetText()));

private void RadMaskedEditBox_KeyDown(object sender, KeyEventArgs e)
{
if ((e.KeyCode == Keys.Insert && e.Modifiers == Keys.Shift)
|| (e.KeyCode == Keys.V && e.Modifiers == Keys.Control))
{
Regex regex = new Regex((sender as RadMaskedEditBoxElement).Mask);
//e.Handled = !(regex.IsMatch(Clipboard.GetText()));
e.SuppressKeyPress = !(regex.IsMatch(Clipboard.GetText()));

}
}

But it is fail for to paste data by using mouse, can you tel me answer for this,
Thanks for You
Vulpes15y ago
Well, any regular expression can only validate the characters that have been entered so far. Clearly, it can have no idea what else the user is going to enter or paste into the textbox.

For example, if the user has entered 'aa' into the box then the regex will give a match.

However, if a third 'a' is then entered it will no longer match.
jayaram15y ago
Thanks for reply
Your answer working for only after entering the data in my textbox but its not working for while I entering the data in my textbox
Vulpes15y ago
The following will match strings containing only lower case letters or commas, as long as there isn't a sequence of at least 3 consecutive lower case letters in the string:

string s1 = "aa,bb,cc,abccd,ttamell,";
string s2 = "aaaaaa,bbbbb,dddd,jkljlkkkkkk";
string s3 = "ddd,asaaaaaaad,rammmmmm,ssssiva";
string r = @"^(?!.*(?'letter'[a-z])\k'letter'{2,})[a-z,]+$";
Console.WriteLine(Regex.IsMatch(s1, r)); // true
Console.WriteLine(Regex.IsMatch(s2, r)); // false
Console.WriteLine(Regex.IsMatch(s3, r)); // false

Negative lookahead is first used to make sure there aren't any sequences of 3 or more letters. The regular expression engine then returns to the beginning of the string and matches it as long as it only contains letters or commas.
jayaram15y ago
Thanks for reply
Its not suitable for my requirement

EX: Valid data is : aa,bb,cc,abccd,ttamell,
I dont want to allow to my textboxes like following type data

Invalid data is: aaaaaa,bbbbb,dddd,jkljlkkkkkk....

I have written in the following way but its working only for when I entering last characters.
And its not working for entering data in middle or starting positions.

****I need to use regex expressions for this requirement*******

private void MaskedEditBox_KeyPress(object sender, KeyPressEventArgs e)
{
var previousCharacter =((RadMaskedEditBoxElement)sender).Text[(sender as RadMaskedEditBoxElement).Text.Length-2];
var nextPreviousCharacter = ((RadMaskedEditBoxElement)sender).Text[(sender as RadMaskedEditBoxElement).Text.Length-1];
if (e.KeyChar.ToString().ToLower() == previousCharacter.ToString().ToLower() && e.KeyChar.ToString().ToLower() == nextPreviousCharacter.ToString().ToLower())
{

}
}
Vulpes15y ago
The following will match any 3 or more consecutive occurrences of the same letter in a given string:

string s = "ddd,asaaaaaaad,rammmmmm,ssssiva";
string r = @"(?'letter'[a-zA-z])\k'letter'{2,}";
MatchCollection mc = Regex.Matches(s, r);
foreach(Match m in mc) Console.WriteLine(m.Value);

The output should be:

ddd
aaaaaaa
mmmmmm
ssss
jayaram15y ago
Thanks for reply
Can you give me RegexExpression for if any three alphabets are the same(more than 3) it shouldn't be allowed.
E.g. ddd,asaaaaaaad,rammmmmm,ssssiva
Vulpes15y ago
I'm not familiar with the Telerik RadMaskedEditBox control but, if it's anything like the one in the .NET framework, when it should have a PromptChar property (or similar) which will default to an underscore. If you set this to a space instead, then it should remove the underscores.

Pasting characters in is a problem with any input validation scheme.

One thing you could do is to disable the Telerik control's context menu by setting its ShortcutsEnabled property (if it has one) to 'false' and only allow pasting via either the standard Shift-Insert or Ctrl-V keyboard shortcuts.

You can then trap these keys and validate the characters in the clipboard before they're actually pasted in with code such as this (I'm assuming the Telerik control has a KeyDown event and KeyEventArgs parameter, or similar):

private void RadMaskedEditBox_KeyDown(object sender, KeyEventArgs e)
{
if ((e.KeyCode == Keys.Insert && e.Modifiers == Keys.Shift)
|| (e.KeyCode == Keys.V && e.Modifiers == Keys.Control))
{
Regex regex = new Regex((sender as RadMaskedEditBoxElement).Mask);
e.Handled = !(regex.IsMatch(Clipboard.GetText()));
}
}
jayaram15y ago
Thanks For reply
Requirement 1:

I used Telerik Controls in My application,

RadMaskedEditBox.Mask="LLLLL" for letters
RadMaskedEditBox.Mask="####" for digits
RadMaskedEditBox.MaskType=Standered

In this situation I am getting underscores in my textbox depending on how many L's or #'s in Mask property, so Can you tel me how to remove those '_' OR
Give me another best way to do my requirement.

Requirement 2:
And I done another process for my requirement, I have written this code in KeyPress event, this is working for all my requirements but while I am using copy or cut then this is useless
radmaskededitbox_keypress(........)
{
Regex regex = new Regex((sender as RadMaskedEditBoxElement).Mask);
e.Handled = !(regex.IsMatch(e.KeyChar.ToString()));
}

so tel me the best way to do this ,
***Actually I need to do all this things by using Regex expressions***
Vulpes15y ago
I imagine you must be used a custom or third party MaskedTextBox as the standard WF version doesn't have a MaskType property.

If it did and Regex were one of the options, then life would be a little easier :)
jayaram15y ago
My application is windows application but I dont want to write code like by using if conditions I can do this way but my requirement is with regex expressions, actually I used masked textboxes and I am writing these expressions in Mask property and MaskType is Regex.
ex:Masktexbox.Mask = "^[A-Za-z]"
Masktexbox.MaskType is Regex
Vulpes15y ago
If it's a Windows Forms application, then there's an example here on MSDN (http://msdn.microsoft.com/en-us/library/system.windows.forms.control.keydown.aspx) which prevents non-numeric characters from being entered at all.