From http://www.w3schools.com (Copyright Refsnes Data)

.NET Mobile Input Validation

Validation Controls are used to validate the data entered by a user.

Validation Controls

Validation controls are used to validate the data entered by a user.

Validation controls allow you to validate an input control (like a TextBox), and display a message when validation fails.

Each validation control performs a specific type of validation (like validating against a specific value or a range of values).

By default, page validation is performed when a command control is clicked. You can prevent validation when a control is clicked by setting the CausesValidation property to false.

Validating Input

This page has two forms:

<%@ Page
Inherits=
"System.Web.UI.MobileControls.MobilePage"%>
<%@ Register
TagPrefix="Mobile"
Namespace="System.Web.UI.MobileControls"
Assembly="System.Web.Mobile" %>

<script runat="server">

Sub Page2(Sender as Object,E as EventArgs)
If Page.IsValid Then
  ActiveForm=f2
  text2.Text="You are " & age.text & " years old"
end if
End Sub

</script>

<Mobile:Form id="f1" runat="server">

<Mobile:CompareValidator runat="server"
  ControlToValidate="age"
  Type="Integer"
  ValueToCompare="18"
  Operator="GreaterThanEqual">
You must be at least 18
</Mobile:CompareValidator>

<Mobile:Label runat="server">Age?</Mobile:Label>
<Mobile:TextBox id="age" runat="server" />
<Mobile:Command OnClick="Page2" runat="server">
Submit</Mobile:Command>
</Mobile:Form>

<Mobile:Form id="f2" runat="server">
<Mobile:Label id="text2" runat="server" />
</Mobile:Form>

The first form has a label with the text "Age?", an input box to input the age, and a submit button.

The second page is activated by the submit button on the first page, and displays a response.

If the input validates as error, an error message is displayed.

When the application runs on a mobile device, the two pages will display like this:

Form 1

Age?

Form 2

You are 21 years old

The ValidationSummary Control

The previous example used a CompareValidator control to validate an input field. The field to validate was defined by the attribute ContolToValidate.

You can also use a ValidationSummary control with the attribute FormToValidate, to validate all the input of a form.

This way you can display a summary of errors instead of one error at the time.

Validation Controls Reference

Name	Function
CompareValidator	Compares two values
CustomValidator	Provides custom validation
RangeValidator	Validates a range
RegularExpressionValidator	Validates an expression
RequiredFieldValidator	Validates required data
ValidationSummary	Displays a validation summary

For a full control reference, including properties methods, events, and more examples, please refer to the "Mobile Reference" page.