RequiredFieldValidator Class
Makes the associated input control a required field.
For a list of all members of this type, see RequiredFieldValidator Members.
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
[Visual Basic] Public Class RequiredFieldValidator Inherits BaseValidator [C#] public class RequiredFieldValidator : BaseValidator [C++] public __gc class RequiredFieldValidator : public BaseValidator [JScript] public class RequiredFieldValidator extends BaseValidator
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.
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.
For additional information on validation controls, see BaseValidator.
Example
[Visual Basic, C#] The following example demonstrates how to use the RequiredFieldValidator control to make sure that the user enters a value into the text box.
[Visual Basic] <%@ Page Language="VB" AutoEventWireup="True" %> <html> <head> <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 runat="server"> <h3>RequiredField Validator Example</h3> <table bgcolor="#eeeeee" cellpadding="10"> <tr valign="top"> <td colspan="3"> <asp:Label ID="lblOutput" Text="Fill in the required field below" runat="server"/> <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> [C#] <%@ Page Language="C#" AutoEventWireup="True" %> <html> <head> <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 runat="server"> <h3>RequiredField Validator Example</h3> <table bgcolor="#eeeeee" cellpadding="10"> <tr valign="top"> <td colspan="3"> <asp:Label ID="lblOutput" Text="Fill in the required field below" runat="server"/> <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>
[C++, JScript] No example is available for C++ or JScript. To view a Visual Basic or C# example, click the Language Filter button
in the upper-left corner of the page.
Requirements
Namespace: System.Web.UI.WebControls
Platforms: Windows 2000, Windows XP Professional, Windows Server 2003 family
Assembly: System.Web (in System.Web.dll)
See Also
RequiredFieldValidator Members | System.Web.UI.WebControls Namespace | RangeValidator | InitialValue