RequiredFieldValidator Class
Makes the associated input control a required field.
Assembly: System.Web (in System.Web.dll)
[AspNetHostingPermissionAttribute(SecurityAction::InheritanceDemand, Level = AspNetHostingPermissionLevel::Minimal)] [AspNetHostingPermissionAttribute(SecurityAction::LinkDemand, Level = AspNetHostingPermissionLevel::Minimal)] public ref class RequiredFieldValidator : public BaseValidator
<asp:RequiredFieldValidator />
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: |
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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.
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: |
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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. |
<html>
<head>
<script language="C#" runat=server>
void ValidateBtn_Click(Object sender, EventArgs e) {
if (Page.IsValid == true) {
lblOutput.Text = "Required field is filled!";
}
else {
lblOutput.Text = "Required field is empty!";
}
}
</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>
- 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.
System.Web.UI::Control
System.Web.UI.WebControls::WebControl
System.Web.UI.WebControls::Label
System.Web.UI.WebControls::BaseValidator
System.Web.UI.WebControls::RequiredFieldValidator
Windows 7, Windows Vista, Windows XP SP2, Windows XP Media Center Edition, Windows XP Professional x64 Edition, Windows XP Starter Edition, Windows Server 2008 R2, Windows Server 2008, 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.
Note:
Security Note: