ASP.Net RegularExpressionValidator Control

RegularExpressionValidator control: The RegularExpressionValidator control is used to ensure that an input value matches a specified pattern.

·         The validation will not fail if the input control is empty. Use the RequiredFieldValidator control to make the field required.

·         Both server- and client-side validation are performed unless the browser does not support client-side validation or the EnableClientScript property is set to false.

·         You can validate email, URL or can specify your own regular expression to validate against input value.

RegularExpressionValidator additional Properties (Check here for other default properties and sample):

Property	Description
ValidationExpression	Specifies the expression used to validate input control. The expression validation syntax is different on the client than on the server. JScript is used on the client. On the server, the language you have specified is used

  Control usage:

<asp:TextBox runat="server" ID="txtNumber"></asp:TextBox> <asp:RegularExpressionValidator ID="regNumeric" runat="server" ControlToValidate=" txtNumber" ValidationExpression="\d{10}" EnableClientScript="false" ErrorMessage="The entered value must be 10 numeric digits"> </asp:RegularExpressionValidator>

As I mentioned earlier you can also write your own regular expression and then use that with RegularExpressionValidator control. Let’s look at some of the character escapes, metacharacter and quantifiers used to write regular expression:

Character Escapes	Description
\b	Matches a backspace
\t	Matches a tab
\r	Matches a carriage return
\v	Matches a vertical tab
\f	Matches a form feed
\n	Matches a new line
\	Escape character
Metacharacters	Description
.	Matches any character except \n
[abcd]	Matches any character in the set
[^abcd]	Excludes any character in the set
\w	Matches any alphanumeric character and underscore
\W	Matches any non-word character
\s	Matches whitespace characters like, space, tab, new line etc.
\S	Matches any non-whitespace character
\d	Matches any decimal character
\D	Matches any non-decimal character
Quantifier	Description
*	Zero or more matches
+	One or more matches
?	Zero or one matches
{N}	N matches
{N,}	N or more matches
{N,M}	Between N and M matches