Asp.net Validation Control Examples

In this Asp.net validation control tutorial, you learn how to use different validation controls in asp.net application development.

Different type of Form validation controls to validate user input data

• RequiredFieldValidator
• RangeValidator
• CompareValidator
• RegularExpressionValidator
• CustomValidator
• ValidationSummary

Properties of BaseValidator Class

Namespace : System.Web.UI.WebControls
All validation controls are inherited from abstract class BaseValidator : Label, IValidator

• ControlToValidate

  Indicate the ID of the control to be validated.

• Display

  Tells how the error message to be shown

• EnableClientScript

  Indicates if client side validation will occur

• ErrorMessage

  error message string

• IsValid

  Indicates if the value of the control is valid

• ValidationGroup

  logical group of multiple validators

• Text

  if validation fails then the error string to be displayed

• SetFocusOnError

  If validation fails, then the focus should go to the related input control

The RequiredFieldValidator control mak sure that the required field is not empty, normally tied to a textbox control to force input into textbox.

<asp:TextBox ID="txtName" runat="server"> </asp:TextBox>
<asp:RequiredFieldValidator ID="rfvName" runat="server" ErrorMessage="Please enter Name" ControlToValidate="txtName"> </asp:RequiredFieldValidator>

Range Validator is used when we want to validate the value within two range, normally used for datatype like number, date etc.

Here in example we are checking the age range should be within 18 to 30
Syntax of RangeValidator

<asp:TextBox ID="txtAge" runat="server"> </asp:TextBox>
<asp:RangeValidator ID="rvAge" runat="server" 
ErrorMessage="Age should be 18 to 30" ControlToValidate="txtAge"
type="Integer" MinimumValue="18" MaximumValue="30">
</asp:RangeValidator>

Look at the property value of Type, MinimumValue & MaximumValue

CompareValidator control is used to compare a value with value of another control or a fixed value.

Here in example below we are comparing password and re-password is equal

Password <asp:TextBox ID="txtPass" runat="server"> </asp:TextBox>
Confirm  <asp:TextBox ID="txtPassRe" runat="server"> </asp:TextBox>
<asp:CompareValidator ID="cvPass" runat="server" ErrorMessage="Password should match" ControlToValidate="txtPass" ControlToCompare="txtPassRe" Operator="Equal">   
</asp:CompareValidator>

• ControlToValidate

  Id of main control textBox

• ControlToCompare

  Id of control to compare with

• ValueToCompare

  if you want to compare with any fixed value

• Operator

  Equal, NotEqual, GreaterThan, GreaterThanEqual, LessThan, LessThanEqual

RegularExpressionValidator in asp.net example

RegularExpressionValidator is used for validating the user input matching against a pattern of a regular expression

In example below we are checking if user has entered a valid email

<asp:TextBox ID="txtEmail" runat="server"> </asp:TextBox>
<asp:RegularExpressionValidator ID="revEmail" runat="server" ErrorMessage="Invalid Email" ControlToValidate="txtEmail" ValidationExpression="\w+([-+.']\w+)*@\w+([-.]\w+)*\.\w+([-.]\w+)*"> </asp:RegularExpressionValidator>

ValidationExpression is string property that contain the expression, and check if user input is matching the expression, if not then display the ErrorMessage

The CustomValidator control allows writing any type of validation logic in your .net code then calling that method in CustomValidator

<asp:TextBox ID="txtCustom" runat="server" ></asp:TextBox>
<asp:CustomValidator ID="cv" runat="server" ControlToValidate="txtCustom"
ErrorMessage="Custom Validator Error" OnServerValidate="cv_ServerValidate"> </asp:CustomValidator>

protected void cv_ServerValidate(object source,
 ServerValidateEventArgs args)
{
if (args.Value == "webtrainingroom")
    args.IsValid = true;
else
    args.IsValid = false;
}

ValidationSummary control is for displaying all validation error in one place, simply place the ValidationSummary control in your form where you want all message to be displayed

<asp:ValidationSummary ID="vsForm" runat="server" 
DisplayMode = "BulletList" ShowSummary = "true" />

You may also read how validation in Asp.Net MVC works.