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I have a regular expression to validate email address. Here it is....

string pattern = "^[^@]+@([-\\w]+\\.)+[A-Za-z]{2,4}$";

System.Text.RegularExpressions.Match match = Regex.Match(txtEmailChecking.Text.Trim(), pattern, RegexOptions.None);
            if (match.Success)
                MessageBox.Show("Success", "Checking");
                MessageBox.Show("Fail", "Checking");

But this expression will allow capital letters in email address. How can I restrict that?

Besides that , this expression allows more than one @. How can I fix this?

Thanks for your support

Updated 16-Apr-21 11:48am

if it is Windows Application
set property of Textbox
CharacterCasing = Lower

it will automatically convert uppercase letters to lowercase.

string pattern="^([0-9a-zA-Z]([-.\w]*[0-9a-zA-Z])*@([0-9a-zA-Z][-\w]*[0-9a-zA-Z]\.)+[a-zA-Z]{2,3})$";

and verify it when textbox's Leave event fire. at a time when you are writing it will allow mistakes like '@' is two time but when you will leave textbox it will give error.

if you do not want '@' at time of keypress event then on key press event you should handle '@' keychar if it's used second time. you can check if '@' is already exist in string using below function

Happy Coding!
Sebastian T Xavier 19-Sep-12 7:51am
This is really informative; thanks... My +5 for it. I have another problem. My expression allows more than one @.
Aarti Meswania 19-Sep-12 8:05am
please check updated solution may it be useful for second problem[^]

check this website for regular expressions

vote if it helps you
Hi everyone,

I see your regular expression knowledge is really low. Am sure that you copied it from someone else :) Not to worry, you can learn regular expressions really fast.

First things first, you don't normally validate for capitals in e-mail. Instead, what you do is, when you save it into your database, you case it to lowercase using string.ToLower()[^] method.

But in case, you really want to validate that with that expression of yours, all you have to do is remove A-Z from your expression. It would look like;
string pattern = "^[^@]+@([-\\w]+\\.)+[a-z]{2,4}$"

If you like to read about regular expressions more, I found these links to be really helpful. They explain things very clearly, makes it easy to understand.
Regular Expressions - User Guide[^]
jQuery RegEx Examples to use with .match()[^]
Regular Expression Basic Syntax Reference[^]

Hope this helps, regards :)
Sebastian T Xavier 19-Sep-12 8:19am
This is definitely NOT going to work , as I have already tried this.
CodeHawkz 19-Sep-12 11:10am
:D I'd bet on it that your regular expression is not validating capital letters. If you want some other error to be fixed let me know. Good luck
Regex : <pre>"^[a-z0-9._%+-]+@[a-z0-9.-]+\\.[a-z]{2,4}$"

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