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RequiredFieldValidator Control

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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.


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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