What is the proper way to deal with this ASP.NET validation?

Question

I have conditional validation that I need to perform. The logic is supposed to work like this:

If radio button 1 is selected, textbox1 is required.
If radio button 2 is selected, dropdownlist1 is required.

What is the best way to accomplish this?

Answer 1

Use a CustomValidator.

Answer 2

Client-side using JQuery validation plugin. Adjust the names to fit those given by ASP.NET if using ASP.NET controls. Server-side is relatively easy - check which radio is selected and make sure that the value of the textbox or dropdown list is non-null.

$(function() {
   $('form').validate( {
      rules: {
         required-textbox: function() {  return $('#radio_yes:checked').size(); }
         required-ddl: function() { return $('#radio_no:checked').size(); }
      }
   });
})


<input type='radio' id='radio_yes' name='radio' value='1' /> Choice 1
<input type='radio' id='radio_no' name='radio' value='2' /> Choice 2

<input type='text' id='textinp' name='textinp' class='required-textbox' />
<select id='ddl' name='ddl' class='required-ddl'>
   <option ... />
</select>

You could also do this with a CustomValidator -- again using jQuery client-side. Again, the server-side functions are trivial (and basically the same as the other case).

function validateTextBox(source, args)
{
    args.IsValid = $('[id$="radio_yes"]:checked').size() && $(source).val();
}

function validateDDL(source, args)
{
    args.IsValid = $('[id$="radio_no"]:checked').size() && $(source).val();
}

<asp:RadioButton ID="radio_yes" runat="server" GroupName="radio" /> Choice 1
<asp:RadioButton ID="radio_no" runat="server" GroupName="radio" /> Choice 2

<asp:TextBox ID="textbox" runat="server" />
<asp:CustomValidator ID="textboxValidator" runat="server"
     ControlToValidate="textbox"
     ClientValidationFunction="validateTextBox"
     OnServerValidate="ddl_Validate"
     Display="Static"
     ErrorMessage="*" />

<asp:DropDownList ID="ddl" runat="server">
 ....
</asp:DropDownList>
<asp:CustomValidator ID="ddlValidator" runat="server"
     ControlToValidate="ddl"
     ClientValidationFunction="validateDDL"
       OnServerValidate="textbox_Validate"
       Display="Static"
       ErrorMessage="*" />