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RequiredFieldValidator Class

Provides control capability to validate whether the value of the associated input control is different from its initial value.

Namespace: System.Web.UI.MobileControls
Assembly: System.Web.Mobile (in

public class RequiredFieldValidator : BaseValidator
public class RequiredFieldValidator extends BaseValidator
public class RequiredFieldValidator extends BaseValidator

This class behaves identically to the ASP.NET System.Web.UI.WebControls.RequiredFieldValidator control.

By default, Command controls on a form raise validator controls on the form to perform validation when the form is submitted to the server. To disable automatic validation, set the CausesValidation property on the Command to false.

The following code example requires a user to enter a number from 1 to 23. It uses both the RangeValidator and the RequiredFieldValidator to validate user entries.

<%@ Page Language="C#" 
    Inherits="System.Web.UI.MobileControls.MobilePage" %>
<%@ Register TagPrefix="mobile" 
    Assembly="System.Web.Mobile" %>

<script runat="server">
    void Page_Load(Object sender, EventArgs e)
        string uNameExpr = "^[a-zA-Z](.{1,9})$";
        string phoneExpr = 
            "((\\(\\d{3}\\) ?)|(\\d{3}-))?\\d{3}-\\d{4}";
        // Define validation expressions.
        RegExprVal1.ValidationExpression = uNameExpr;
        RegExprVal2.ValidationExpression = phoneExpr;
        ReqFldVal1.Text = "User name is required";
        RegExprVal1.Text = "Must be between 2 to 10 characters";
        RegExprVal2.Text = "Please provide a valid number: (425) 555-0187";
        // ErrorMessages appear in ValidationSummary.
        RegExprVal1.ErrorMessage = "Incorrect UserName format. Name" +
            " can be 2 to 10 characters long";
        ReqFldVal1.ErrorMessage = "User name required";
        RegExprVal2.ErrorMessage = 
            "Please provide a valid number: (000) 000-0000";
    void OnCmdClick(Object sender, EventArgs e)
        if (Page.IsValid)
            ActiveForm = Form2;

<html xmlns="" >
    <mobile:Form runat="server" id="Form1" >
        <mobile:Label runat="server" id="Label1" 
            Text="Your information" 
            StyleReference="title" />   
        <mobile:Label runat="server" id="Label2" 
            Text="User Name (required)" />
        <mobile:Textbox  runat="server" id="TextBox1"/>
        <mobile:RequiredFieldValidator runat="server" 
            id="ReqFldVal1" ControlToValidate="TextBox1" />
        <mobile:RegularExpressionValidator runat="server" 
            id="RegExprVal1" ControlToValidate="TextBox1" />
        <mobile:Label runat="server" id="Label3" Text="Phone" />
        <mobile:Textbox  runat="server" id="TextBox2"/>
        <mobile:RegularExpressionValidator runat="server" 
            id="RegExprVal2" ControlToValidate="TextBox2" />
        <mobile:ValidationSummary ID="ValidationSummary1" 
            FormToValidate="Form1" HeaderText="Error Summary:" 
            runat="server" />
        <mobile:Command runat="server" id="Command1" 
            Text="Submit" OnClick="OnCmdClick"/>

    <mobile:Form id="Form2" runat="server" >
        <mobile:Label ID="Label4" runat="server" Text="Thank You." />


Any public static (Shared in Visual Basic) members of this type are thread safe. Any instance members are not guaranteed to be thread safe.

Windows 98, Windows 2000 SP4, Windows Millennium Edition, Windows Server 2003, Windows XP Media Center Edition, Windows XP Professional x64 Edition, Windows XP SP2, Windows XP Starter Edition

The .NET Framework does not support all versions of every platform. For a list of the supported versions, see System Requirements.

.NET Framework

Supported in: 2.0, 1.1