RequiredFieldValidator Control, asp:RequiredFieldValidator Control

RequiredFieldValidator validator control is used to make a field as mandatory in the form. Without filling the field user can't submit the form.

Following are some basic properties of all Validator controls

ControlToValidate	Gets or sets the input control to validate (eg. The ID value of asp:TextBox control).
Display	Dynamic/Static. Used to indicate how the area of error message will be allocated. Dynamic: Error message area will only be allocated when error will be displayed. Static: Error messagea area will be allocated in either case.
Enabled	true/false. Gets or sets whether to enable the validation control or not.
ErrorMessage	Gets or sets the text of the error message that will be displayed when validation fails (This is displayed when ValidationSummary validatoin control is used.).
Text	Gets or sets the description of the error message text.
ValidationGroup	Gets or sets the validation group it belongs to. This is used to group a set of controls.
SetFocusOnError	true/false. Used to move focus on the control that fails the validation.

DEMO : RequiredFieldValidator

Show Source Code

Write into TextBox


    <asp:Label ID="lbl" AssociatedControlID="TextBox1" runat="Server" Text="Write into TextBox"></asp:Label>
    <asp:TextBox ID="TextBox1" runat="Server"></asp:TextBox>
    <asp:RequiredFieldValidator ID="req1" runat="Server" ControlToValidate="TextBox1" ErrorMessage="TextBox is Mandatory field" Text="Please write something in the Box."></asp:RequiredFieldValidator>
    <asp:Button ID="btnSubmit" runat="Server" OnClick="ChangeLabelText" Text="Change Label Text" />                
    <asp:ValidationSummary ID="ValidationSummary" runat="Server" ShowMessageBox="true" />