<Validate Type="CheckboxList">

The CheckboxList validator prevents the form from being submitted unless at least one item in the target <CheckBoxList> is checked. Use it when "you must pick at least one" is the right rule — for example, "select at least one notification preference."

Server-side only

This validator runs on the server. The form must pass all client-side validation and POST back before the CheckboxList check fires. The source explicitly disables client-side validation in its constructor (EnableClientScript = False).

Example

<AddForm>
  <SubmitCommand CommandText="INSERT INTO Users(FirstName, LastName, FavColors)
                              VALUES(@FirstName, @LastName, @FavColors)" />
  <table>
    <tr>
      <td>
        <Label For="txtFirstName" Text="First Name" />
        <TextBox Id="txtFirstName" DataField="FirstName" DataType="string" />
      </td>
    </tr>
    <tr>
      <td>
        <Label For="cblColors" Text="Favorite Color(s)" />
        <CheckBoxList Id="cblColors" DataField="FavColors" DataType="string">
          <ListItem Value="Red">Red</ListItem>
          <ListItem Value="Green">Green</ListItem>
          <ListItem Value="Blue">Blue</ListItem>
        </CheckBoxList>
        <Validate Type="CheckboxList" Target="cblColors" Text="**"
                  Message="Please select at least one color" />
      </td>
    </tr>
    <tr>
      <td colspan="2">
        <AddButton Text="Add" />&nbsp;<CancelButton Text="Cancel" />
        <ValidationSummary />
      </td>
    </tr>
  </table>
</AddForm>

Properties

Property	Values	Default	Description
Type *	CheckboxList		Identifies this as a CheckboxList validator
Target *	control ID		ID of the <CheckBoxList> to validate
CssClass	string		CSS class name(s) for styling the validator's error display
Display	Static Dynamic	Dynamic	Whether the validator reserves layout space when no error is shown
Height	size		Height of the validator's error display
Message	string		Text shown in the <ValidationSummary> when validation fails
Text	string		Text shown inline at the validator's location when validation fails
Width	size		Width of the validator's error display

* Required property

No EnableClientScript

This validator runs server-side only and does not expose EnableClientScript — the source forces it to False in the constructor.

Deprecated Properties

These properties use ASP.NET inline styling and are no longer recommended for modern web development. Use the CssClass property to apply CSS classes or the Style property for inline CSS instead.

Property	Values	Description
BackColor	color name | #dddddd	Background color of the validator's error display
BorderColor	color name | #dddddd	Border color
BorderStyle	NotSet None Dotted Dashed Solid Double Groove Ridge Inset Outset	Border style
BorderWidth	size	Border width
Font-Bold	True False	Bold text
Font-Italic	True False	Italic text
Font-Names	string	Font family name
Font-Overline	True False	Overline text decoration
Font-Size	XX-Small X-Small Small Medium Large X-Large XX-Large or size	Font size
Font-Strikeout	True False	Strikethrough text decoration
Font-Underline	True False	Underline text decoration
ForeColor	color name | #dddddd	Text color of the error display

Property Details

• Type: Set to CheckboxList to identify this as a CheckboxList validator.

• Target: The ID of the <CheckBoxList> control whose selection should be checked. The control must be a <CheckBoxList> (or another ListControl) — the validator throws an exception at runtime if pointed at any other control type.

• Message: The error text shown in the <ValidationSummary> (if you have one) when validation fails. If no <ValidationSummary> is present, this text appears at the validator's location instead.

• Text: The text shown inline at the validator's location when validation fails. Used together with Message and <ValidationSummary>: a short inline marker (*, **, or an icon) at the validator + the full sentence in the summary block.

• Display: Whether the validator reserves layout space even when no error is shown. Dynamic (the default) collapses to no space until validation fails. Static always reserves space.