How to make a Textbox required IF a Checkbox is checked

user_193830 0
Viewed 19936

How can I make a textbox required if a checkbox is checked?

I figure I could write a custom validator, but I was hoping to avoid a full post back to check the validation if possible... I was thinking AJAX had something built in for this scenario, but I've been unable to find it. I'm thinking straight JavaScript would also be a solution, but I could use a head start if that's the best approach.

validation asp.net .net
6 Answers

The JavaScript to handle this isn't very difficult.

Given the following ASP controls:

<asp:TextBox ID="txtSubject" runat="server" />
<asp:CheckBox ID="chkSubjectRequired" runat="server" OnClick="updateValidator();" />
<asp:RequiredFieldValidator ID="rfvSubject" ControlToValidate="txtSubject" ErrorMessage="You must enter a subject." runat="server" />

Add the following JavaScript function:

<script language="javascript" type="text/javascript">
    function updateValidator() {
        var enableValidator = !event.srcElement.status;
        var rfvSubject = document.getElementById('rfvSubject');
        ValidatorEnable(rfvSubject, enableValidator);
    }
</script>

That's all there is to it. You will also want to add the following code to your Page Load event, so that if the user has JavaScript disabled, your required field validator is still turned on or off properly:

rfvSubject.Enabled = chkSubjectRequired.Checked
user_1721960

You could make a custom validator, and then wrap those two controls in an UpdatePanel. That would turn it into an AJAX call for you. Kinda a waste, but it saves you having to write the JavaScript yourself.

Also, if you hate writing JS as much as I do, you should try jQuery instead.

user_400150

There is already a customvalidator validator control, which can fire a client-side javascript method to evaluate the value, or a server-side method to compare the values.

This has an example: http://msdn.microsoft.com/en-us/library/a0z2h4sw%28VS.80%29.aspx Client property explained here: http://msdn.microsoft.com/en-us/library/system.web.ui.webcontrols.customvalidator.clientvalidationfunction.aspx Server event here: http://msdn.microsoft.com/en-us/library/system.web.ui.webcontrols.customvalidator.servervalidate.aspx

You can put code in to cross-reference the checkbox value.

HTH.

user_2317160

You must use CustomValidator and use ClientIDMode="Static" in checkbox and textbox.

<asp:TextBox ID="txtSubject" ClientIDMode="Static" runat="server" />
<asp:CheckBox ID="chkSubjectRequired" ClientIDMode="Static" runat="server" />
<asp:CustomValidator ID="valid1" runat="server" 
           ClientValidationFunction="validateCheckboxCheck" 
           ErrorMessage="You must write anything.">
</asp:CustomValidator>

And write below script tag for function (require jQuery)

<script type="text/javascript">
function validateCheckboxCheck(source, args) {
            if ($("#chkSubjectRequired").is(":checked")) {
                if ($("#txtSubject").val()==="") {
                    // return false for error message
                    args.IsValid = false;
                } else {
                    // return true
                    args.IsValid = true;
                }
            } else {
                // return true
                args.IsValid = true;
            }
        }
</script>
user_8334090

You'll need to check for it in whatever validation routine you're currently using, both client and server-side.

user_636230
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