Question

I hava an ASP.NET Web Forms application.

My goal is to disable the submit button btnFinish upon user click, in order to avoid multiple submits.

<asp:Button ID="btnFinish" runat="server" Text="Finish" UseSubmitBehavior="false" 
CausesValidation="true" CommandName="MoveComplete" CssClass="buttonStyle"/>

The Javascript function is:

 function Validate(btnFinishId) {

            btnObj = document.getElementById(btnFinishId)

            if (Page_IsValid) {
                btnObj.disabled = true
            }
            else {
                 alert('Page has some validation error');
                 }

            // this is to prevent the actual submit
            e.preventDefault();

            return false;
    };

btnFinish is placed within a FinishNavigationTemplate in a ASP.NET Wizard Control.
Therefore, in order to avoid runtime errors, I need to get the ClientID of the control programmatically and then add it to the OnClientClick event of the button:

Button btFinish = MyWizard.FindControl("FinishNavigationTemplateContainerID$btnFinish") as Button;

if (btFinish != null){
   btFinish.Attributes.Add("onclientclick", "Validate('" + btFinish.ClientID + "');");
}

But it does not work. I use Firebug to check the page rendered by the browser but although the source code looks perfect, upon click the Javascript function is not executed.

If in the Javascript function I replace Validate(btnFinishId) with Validate() and instead of using the code behind to add the OnClientClick I write:

 <asp:Button OnClientClick="Validate();" "ID="btnFinish" runat="server" Text="Finish" UseSubmitBehavior="false" 
    CausesValidation="true" CommandName="MoveComplete" CssClass="buttonStyle"/>

The function is executed but of course does not do what I want, because the button Id is missing. Anybody has a solution?

Answer 1

You’re on the right track. Something like this should work:

<script type="text/javascript">
    validate = function(btn){

        //trigger client-side validation
        var valid = Page_ClientValidate("");

        //disable the button if the form is valid
        btn.disabled = valid;

        //trigger postback if the form is valid
        //otherwise do nothing
        return valid;                        
    }
</script>
<asp:Button ID="btnFinish" runat="server" Text="Finish" OnClientClick="return validate(this);" OnClick="btnFinish_Click" ... />

It looks kind of backwards, but you could shorten the function like this:

<script type="text/javascript">
    validate = function(btn){
        btn.disabled = Page_ClientValidate("");                        
        return btn.disabled;                        
    }
</script>