Definition and Usage

The RequiredFieldValidator control is used to make an input control a required field.

With this control, the validation fails if the input value does not change from its initial value. By default, the initial value is null.

Note: Leading and trailing spaces of the input value are removed before validation.

Note: The InitialValue property does not set the default value for the input control. It indicates the value that you do not want the user to enter in the input control.

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Properties

Property	Value	Description
Alignment	left center right	Optional. How to align the control
BackColor	rgb(x,x,x) #xxxxxx colorname	Optional. A background color for the control
ControlToValidate	id_of_target_control	Optional. The id of the control to validate
Display	None Static Dynamic	Optional. The display behavior for the validation control. Legal values are: None (the control is not displayed. Used to show the error message only in the ValidationSummary control) Static (the control displays an error message if validation fails. Space is reserved on the page for the message even if the input passes validation Dynamic (the control displays an error message if validation fails. Space is not reserved on the page for the message if the input passes validation Dynamic is default
ErrorMessage	errortext_for_summary	Optional. The text to display in the ValidationSummary control when validation fails
ForeColor	rgb(x,x,x) #xxxxxx colorname	Optional. A foreground color for the control
Font-Bold	false true	Optional. Specifies whether or not the text in the control should be bold
Font-Italic	false true	Optional. Specifies whether or not the text in the control should be italic
Font-Name	fontname	Optional. Specifies the font name of the text in the control
Font-Size	normal small large	Optional. Specifies the font size of the text in the control
id	unique_name	Optional. A unique id for the control
InitialValue	initial_value	Optional. Specifies the starting value of the input control. Default value is null
runat	"server"	Required. Specifies that the control is a server control
StyleReference	name_of_style_element	Optional. Specifies a reference to a style to be applied to the control
Text	errortext	Optional. The message to display when validation fails
Wrapping	wrap nowrap	Optional. Specifies whether or not the text in the control should wrap

Example 1

The following example contains two forms in an .aspx file. The first form has a label with the text "Please enter a number from 1 through 100", an input box to input a number, a RangeValidator control that checks that the input value is a number from 1 through 100, a RequiredFieldValidator control that checks that the input field isn't empty, and a submit button. The second page is activated by the submit button on the first page, and displays a response. If the input value validates as an error, an error message is displayed:

<%@ 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   lbl2.Text="You entered number " & txt1.text end if end sub </script> <Mobile:Form id="f1" runat="server">   <Mobile:Label runat="server">   Please enter a number from 1 through 100   </Mobile:Label>   <Mobile:TextBox id="txt1" runat="server"/>   <Mobile:RangeValidator   ControlToValidate="txt1"   Type="Integer"   MaximumValue="100"   MinimumValue="1"   Text="Invalid number"   runat="server" />   <Mobile:RequiredFieldValidator   ControlToValidate="txt1"   Text="A number is required"   runat="server" />   <Mobile:Command runat="server"   OnClick="page2">Submit   </Mobile:Command> </Mobile:Form> <Mobile:Form id="f2" runat="server">   <Mobile:Label id="lbl2" runat="server" /> </Mobile:Form>

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