asp.net validation basics
satya - Wednesday, May 23, 2007 1:55:17 PM
requiredfieldvalidator sample
<asp:RequiredFieldValidator 
   id=thisValidatorControlId
   ControlToValidate=controlToValidateId
   ErrorMessage="UserName is a required field." 
   EnableClientScript=true 
   Display=None Runat=server/>
satya - Wednesday, May 23, 2007 1:56:40 PM
Validation summary
<asp:ValidationSummary 
   id=ValSummary 
   HeaderText="The following errors were found:" 
   ShowSummary=True 
   DisplayMode=List 
Runat=server/>
satya - Wednesday, May 23, 2007 1:58:42 PM
validation controls
RequiredFieldValidator
RangeValidator
CustomValidator
ValidationSummary
RegularExpressionValidator
satya - Wednesday, May 23, 2007 2:00:57 PM
See here for a summary of the validation controls