RequiredFieldValidator Class (System.Web.UI.WebControls)

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.NET Framework Class Library

RequiredFieldValidator Class

Updated: November 2007

Makes the associated input control a required field.

Namespace: System.Web.UI.WebControls
Assembly: System.Web (in System.Web.dll)

Syntax

Visual Basic (Declaration)

<AspNetHostingPermissionAttribute(SecurityAction.InheritanceDemand, Level := AspNetHostingPermissionLevel.Minimal)> _
<AspNetHostingPermissionAttribute(SecurityAction.LinkDemand, Level := AspNetHostingPermissionLevel.Minimal)> _
Public Class RequiredFieldValidator _
    Inherits BaseValidator

Visual Basic (Usage)

Dim instance As RequiredFieldValidator

[AspNetHostingPermissionAttribute(SecurityAction.InheritanceDemand, Level = AspNetHostingPermissionLevel.Minimal)]
[AspNetHostingPermissionAttribute(SecurityAction.LinkDemand, Level = AspNetHostingPermissionLevel.Minimal)]
public class RequiredFieldValidator : BaseValidator

Visual C++

[AspNetHostingPermissionAttribute(SecurityAction::InheritanceDemand, Level = AspNetHostingPermissionLevel::Minimal)]
[AspNetHostingPermissionAttribute(SecurityAction::LinkDemand, Level = AspNetHostingPermissionLevel::Minimal)]
public ref class RequiredFieldValidator : public BaseValidator

/** @attribute AspNetHostingPermissionAttribute(SecurityAction.InheritanceDemand, Level = AspNetHostingPermissionLevel.Minimal) */
/** @attribute AspNetHostingPermissionAttribute(SecurityAction.LinkDemand, Level = AspNetHostingPermissionLevel.Minimal) */
public class RequiredFieldValidator extends BaseValidator

JScript

public class RequiredFieldValidator extends BaseValidator

ASP.NET

<asp:RequiredFieldValidator />

Remarks

Use this control to make an input control a required field. The input control fails validation if its value does not change from the InitialValue property upon losing focus.

Multiple validators can be associated with the same input control. For example, a RequiredFieldValidator can be used to ensure input to a control, while at the same time a RangeValidator can be used to ensure that the input is within a specified data range.

Note:
When you use the RequiredFieldValidator control inside an UpdatePanel control, make sure that the validator control and the control it is associated with are in the same panel. For more information about using the UpdatePanel control for partial-page updates, see Partial-Page Rendering Overview.

For additional information on validation controls, see BaseValidator.

Accessibility

The markup rendered by default for this control might not conform to accessibility standards such as the Web Content Accessibility Guidelines 1.0 (WCAG) priority 1 guidelines. For details about accessibility support for this control, see ASP.NET Controls and Accessibility.

Topic	Location
How to: Disable Validation for ASP.NET Server Controls	Building ASP .NET Web Applications
How to: Disable Validation for ASP.NET Server Controls	Building ASP .NET Web Applications
How to: Disable Validation for ASP.NET Server Controls	Building ASP .NET Web Applications in Visual Studio
How to: Display Server Side Custom Validation Messages for ASP.NET Server Controls	Building ASP .NET Web Applications
How to: Display Server Side Custom Validation Messages for ASP.NET Server Controls	Building ASP .NET Web Applications
How to: Display Server Side Custom Validation Messages for ASP.NET Server Controls	Building ASP .NET Web Applications in Visual Studio
How to: Format Validation Error Messages for ASP.NET Server Controls	Building ASP .NET Web Applications
How to: Format Validation Error Messages for ASP.NET Server Controls	Building ASP .NET Web Applications
How to: Format Validation Error Messages for ASP.NET Server Controls	Building ASP .NET Web Applications in Visual Studio
How to: Specify Layout for In-Place Messages On ASP.NET Server Controls	Building ASP .NET Web Applications
How to: Specify Layout for In-Place Messages On ASP.NET Server Controls	Building ASP .NET Web Applications
How to: Specify Layout for In-Place Messages On ASP.NET Server Controls	Building ASP .NET Web Applications in Visual Studio
How to: Test Validity Programmatically for ASP.NET Server Controls	Building ASP .NET Web Applications
How to: Test Validity Programmatically for ASP.NET Server Controls	Building ASP .NET Web Applications
How to: Test Validity Programmatically for ASP.NET Server Controls	Building ASP .NET Web Applications in Visual Studio
How to: Validate Against a Data Type for ASP.NET Server Controls	Building ASP .NET Web Applications
How to: Validate Against a Data Type for ASP.NET Server Controls	Building ASP .NET Web Applications
How to: Validate Against a Data Type for ASP.NET Server Controls	Building ASP .NET Web Applications in Visual Studio
How to: Validate Against a Range of Values for ASP.NET Server Controls	Building ASP .NET Web Applications
How to: Validate Against a Range of Values for ASP.NET Server Controls	Building ASP .NET Web Applications
How to: Validate Against a Range of Values for ASP.NET Server Controls	Building ASP .NET Web Applications in Visual Studio
How to: Validate Against a Specific Value for ASP.NET Server Controls	Building ASP .NET Web Applications
How to: Validate Against a Specific Value for ASP.NET Server Controls	Building ASP .NET Web Applications
How to: Validate Against a Specific Value for ASP.NET Server Controls	Building ASP .NET Web Applications in Visual Studio
How to: Validate Against Patterns for ASP.NET Server Controls	Building ASP .NET Web Applications
How to: Validate Against Patterns for ASP.NET Server Controls	Building ASP .NET Web Applications
How to: Validate Against Patterns for ASP.NET Server Controls	Building ASP .NET Web Applications in Visual Studio
How to: Validate Against Values in a Database for ASP.NET Server Controls	Building ASP .NET Web Applications
How to: Validate Against Values in a Database for ASP.NET Server Controls	Building ASP .NET Web Applications
How to: Validate Against Values in a Database for ASP.NET Server Controls	Building ASP .NET Web Applications in Visual Studio
How to: Validate Programmatically for ASP.NET Server Controls	Building ASP .NET Web Applications
How to: Validate Programmatically for ASP.NET Server Controls	Building ASP .NET Web Applications
How to: Validate Programmatically for ASP.NET Server Controls	Building ASP .NET Web Applications in Visual Studio
How to: Validate Required Entries for ASP.NET Server Controls	Building ASP .NET Web Applications
How to: Validate Required Entries for ASP.NET Server Controls	Building ASP .NET Web Applications
How to: Validate Required Entries for ASP.NET Server Controls	Building ASP .NET Web Applications in Visual Studio
How to: Validate with a Custom Function for ASP.NET Server Controls	Building ASP .NET Web Applications
How to: Validate with a Custom Function for ASP.NET Server Controls	Building ASP .NET Web Applications
How to: Validate with a Custom Function for ASP.NET Server Controls	Building ASP .NET Web Applications in Visual Studio
Walkthrough: Validating User Input in a Web Forms Page	Building ASP .NET Web Applications in Visual Studio
Walkthrough: Validating User Input in a Web Forms Page	Building Applications with Visual Web Developer

Examples

The following example demonstrates how to use the RequiredFieldValidator control to make sure that the user enters a value into the text box.

Security Note:
This example has a text box that accepts user input, which is a potential security threat. By default, ASP.NET Web pages validate that user input does not include script or HTML elements. For more information, see Script Exploits Overview.

Visual Basic

<%@ Page Language="VB" AutoEventWireup="True" %>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
    "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html  >
<head>
    <title>RequiredField Validator Example</title>
<script runat="server">

      Sub ValidateBtn_Click(sender As Object, e As EventArgs) 

         If Page.IsValid Then 

            lblOutput.Text = "Required field is filled!"

         Else 

            lblOutput.Text = "Required field is empty!"

         End If

      End Sub

   </script>

</head>
<body>

   <form id="form1" runat="server">

      <h3>RequiredField Validator Example</h3>

      <table style="background-color:#eeeeee; padding:10">
         <tr valign="top">
            <td colspan="3">
               <asp:Label ID="lblOutput" 
                    Text="Fill in the required field below"
                    runat="server"
                    AssociatedControlID="TextBox1"/>
               <br />
            </td>
         </tr>

         <tr>
            <td colspan="3">
               <b>Credit Card Information</b>
            </td>
         </tr>

         <tr>
            <td align="right">
               Card Number:
            </td>
            <td>
               <asp:TextBox id="TextBox1" 
                    runat="server"/>
            </td>
            <td>
               <asp:RequiredFieldValidator id="RequiredFieldValidator2"
                    ControlToValidate="TextBox1"
                    Display="Static"
                    ErrorMessage="*"
                    runat="server"/> 
            </td>
         </tr>
         <tr>
            <td></td>
            <td>
               <asp:Button id="Button1" 
                    Text="Validate" 
                    OnClick="ValidateBtn_Click" 
                    runat="server"/>
            </td>
            <td></td>
         </tr>
      </table>

   </form>

</body>
</html>

<%@ Page Language="C#" AutoEventWireup="True" %>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
    "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html  >
<head>
    <title>RequiredField Validator Example</title>
<script runat="server">

      void ValidateBtn_Click(Object sender, EventArgs e) 
      {

         if (Page.IsValid) 
         {
            lblOutput.Text = "Required field is filled!";
         }
         else 
         {
            lblOutput.Text = "Required field is empty!";
         }
      }

   </script>

</head>
<body>

   <form id="form1" runat="server">

      <h3>RequiredField Validator Example</h3>

      <table style="background-color:#eeeeee; padding:10">
         <tr valign="top">
            <td colspan="3">
               <asp:Label ID="lblOutput" 
                    Text="Fill in the required field below"
                    runat="server"
                    AssociatedControlID="TextBox1"/>
               <br />
            </td>
         </tr>

         <tr>
            <td colspan="3">
               <b>Credit Card Information</b>
            </td>
         </tr>

         <tr>
            <td align="right">
               Card Number:
            </td>
            <td>
               <asp:TextBox id="TextBox1" 
                    runat="server"/>
            </td>
            <td>
               <asp:RequiredFieldValidator id="RequiredFieldValidator2"
                    ControlToValidate="TextBox1"
                    Display="Static"
                    ErrorMessage="*"
                    runat="server"/> 
            </td>
         </tr>
         <tr>
            <td></td>
            <td>
               <asp:Button id="Button1" 
                    Text="Validate" 
                    OnClick="ValidateBtn_Click" 
                    runat="server"/>
            </td>
            <td></td>
         </tr>
      </table>

   </form>

</body>
</html>

<html>
<head>
   <script language="C#" runat=server>











   </script>

</head>
<body>

<h3><font face="Verdana">RequiredField Validator Sample</font></h3>
<p>

<form runat="server">

   <table bgcolor="#eeeeee" cellpadding=10>
      <tr valign="top">
         <td colspan=3>
            <asp:Label ID="lblOutput" 
                 Text="Fill in the required field below"
                 ForeColor="red" 
                 Font-Name="Verdana" 
                 Font-Size="10" runat=server /><br>
         </td>
      </tr>

      <tr>
         <td colspan=3>
            <font face=Verdana size=2><b>Credit Card Information</b></font>
         </td>
      </tr>

      <tr>
         <td align=right>
            <font face=Verdana size=2>Card Number:</font>
         </td>
         <td>
            <asp:TextBox id=TextBox1 runat=server />
         </td>
         <td>
            <asp:RequiredFieldValidator id="RequiredFieldValidator2"
                 ControlToValidate="TextBox1"
                 Display="Static"
                 Width="100%" runat=server>
                 *
            </asp:RequiredFieldValidator>

         </td>
      </tr>
      <tr>
         <td></td>
         <td>
            <asp:Button id=Button1 
                 text="Validate" 
                 OnClick="ValidateBtn_Click" 
                 runat=server />
         </td>
         <td></td>
      </tr>
   </table>

</form>

</body>
</html>

Permissions

AspNetHostingPermission
for operating in a hosted environment. Demand value: LinkDemand; Permission value: Minimal.
AspNetHostingPermission
for operating in a hosted environment. Demand value: InheritanceDemand; Permission value: Minimal.

Inheritance Hierarchy

System..::.Object
  System.Web.UI..::.Control
    System.Web.UI.WebControls..::.WebControl
      System.Web.UI.WebControls..::.Label
        System.Web.UI.WebControls..::.BaseValidator
          System.Web.UI.WebControls..::.RequiredFieldValidator

Thread Safety

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

Platforms

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

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

Version Information

.NET Framework

Supported in: 3.5, 3.0, 2.0, 1.1, 1.0

Reference

RequiredFieldValidator Members

System.Web.UI.WebControls Namespace

RangeValidator

InitialValue

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