Some important regular expression validators

1) for only characters
<asp:RegularExpressionValidator ID="RegularExpressionValidator6" runat="server" ErrorMessage="Only characters are allowed"  ControlToValidate="txt" ValidationExpression="[A-Za-z]*$"/>

2) for only numbers
<asp:RegularExpressionValidator ID="RegularExpressionValidator1" runat="server" ErrorMessage="Only numbers are allowed" ControlToValidate="txt" ValidationExpression="^\d{0,}$"/>

3) for email ID
<asp:RegularExpressionValidator ID="RegularExpressionValidator1" runat="server" ErrorMessage="Enter a valid EmailID" ControlToValidate="txtUserID"
ValidationExpression="^[A-Za-z0-9](([_\.\-]?[a-zA-Z0-9]+)*)@([A-Za-z0-9]+)(([\.\-]?[a-zA-Z0-9]+)*)\.([A-Za-z]{2,})$" />

4) for password
<asp:RegularExpressionValidator ID="RegularExpressionValidator2" runat="server" ControlToValidate="txtPassword" ValidationExpression="^([a-zA-Z0-9@*#]{6,15})$"
ErrorMessage="Your Password must be between 5 and 15 characters" />
 
5) for date
<asp:RegularExpressionValidator ID="RegularExpressionValidator18" runat="server" SetFocusOnError="true" Font-Size="XX-Small"
ErrorMessage="Enter a valid date" Display="Dynamic" ControlToValidate="txtDOB" ValidationExpression="([012][0-9]
3[01])/(0?[1-9]
1[012])/((19
20)\\d\\d)" />

6) for currency - it allows negative sign, and two digits past decimal
^[-]?([1-9]{1}[0-9]{0,}(\.[0-9]{0,2})?|0(\.[0-9]{0,2})?|\.[0-9]{1,2})$