Question

On my page I have a text box that uses a custom validator:

<asp:CustomValidator ID="cv_Question" ControlToValidate="tb_Question" runat="server" ErrorMessage="*" OnServerValidate="ValidateQuestion" ClientValidationFunction="CheckQuestion" ForeColor="#FF0000" ValidationGroup="CreateUser"></asp:CustomValidator>

The client side validation script that I would like to use always returns 0 for the drop down list SelectedValue, even when the drop down list index has already changed.

I set the drop down list default index to 0 with !Page.IsPostBack

Here is the drop down list:

<asp:DropDownList ID="ddl_Question" runat="server" EnableViewState="true" AutoPostBack="true" onselectedindexchanged="ddl_Question_SelectedIndexChanged">
        <asp:ListItem Selected="False" Text="Select a question" Value="0"></asp:ListItem>
        <asp:ListItem Selected="False" Text="What was the first movie I ever saw?" Value="1"></asp:ListItem>        
        <asp:ListItem Selected="False" Text="What is the middle name of my oldest child?" Value="2"></asp:ListItem>
        <asp:ListItem Selected="False" Text="In what city was my father born?" Value="3"></asp:ListItem>
        <asp:ListItem Selected="False" Text="Who was my favourite cartoon character as a child?" Value="4"></asp:ListItem>
        <asp:ListItem Selected="False" Text="What is my mother's middle name?" Value="5"></asp:ListItem>
        <asp:ListItem Selected="False" Text="In what year did I meet my significant other?" Value="6"></asp:ListItem>
        <asp:ListItem Selected="False" Text="What was my first pet's name?" Value="7"></asp:ListItem>
        <asp:ListItem Selected="False" Text="First name of the maid of honour at my wedding?" Value="8"></asp:ListItem>
        <asp:ListItem Selected="False" Text="First name of my best friend in elementary school?" Value="9"></asp:ListItem>
        <asp:ListItem Selected="False" Text="Name of my all-time favourite movie character?" Value="10"></asp:ListItem>
        <asp:ListItem Selected="False" Text="Create a question" Value="11"></asp:ListItem>
    </asp:DropDownList>

Here is the client side validation:

   <script type="text/javascript" language="javascript">
        function CheckQuestion(sender, args) 
        {        
            var Question =  args.Value.toString();

            <% if(Convert.ToInt32(ddl_Question.SelectedValue) == 11) 
            { %>
                if (Question != "" && Question != null) 
                {
                    args.IsValid = true;
                    return;
                }
                else
                {
                    args.IsValid = false;
                    return;
                }
            <% } 
            else
            { %>
                alert(<%= Convert.ToInt32(ddl_Question.SelectedValue)%>);
                args.IsValid = true;
                return;
            <% } %>
        }
    </script>

I only want to validate the tb_Question if the user has selected “Create a question” from the ddl_Question.

EDIT:

Here is my SelectedIndexChanged method. The tb_Question is made visible when the user selects “Create a question”. This happens before any validation occurs.

protected void ddl_Question_SelectedIndexChanged(object sender, EventArgs e)
    {
        if (Convert.ToInt32(ddl_Question.SelectedValue) == 11)
        {
            Question.Visible = true;
        }
        else
        {
            Question.Visible = false;
        }
    }

Answer 1

Well my recommendation is to use simple JavaScript

So instead of doing that, use JavaScript and maybe jQuery like this

jQuery Nuget: https://nuget.org/packages/jQuery

<script type="text/javascript" src="Scripts/jquery-1.7.2.min.js"></script>
<script type="text/javascript" language="javascript">
    function CheckQuestion(sender, args) 
    {        
        var Question =  args.Value.toString();
        var questionID = '<%= this.ddl_Question.ClientID %>';
        var currentQuestion = $("#" + questionID).val();

        if (currentQuestion == '11')
        { 
            if (Question != "" && Question != null) 
            {
                args.IsValid = true;
                return;
            }
            else
            {
                args.IsValid = false;
                return;
            }
        } 
        else
        {
            alert(currentQuestion);
            args.IsValid = true;
            return;
        }
    }
</script>