ASP.NET - Custom Validator with Dynamic ErrorMessage

Question

I am currently trying to make sure a number entered in a textbox is divisibly by 1.25 or 1.5. The wayI decide weather to mod the number by 1.25 or 1.5 is dependant on what is in another drop down list. For example: If the selected index of a DDL is 1, I mod by 1.5, if it is 2 I mod by 1.25.

However I need to display to the user why the error was thrown. The error message of the custom validator needs to be something like "Number Must be devisible by 1.25" or vice versa.

From what I can tell me code should work. But it doesn't. I read on another forum that taking the source and making the innerText your error message should do the trick. But I must be doing something wrong somewhere. When I step through my javascript function it steps through perfectly. Just no error message. Here is my code:

<asp:CustomValidator ID="ValidateFinHeight" runat="server" CssClass="NormLabel" 
Display="Dynamic" 
ControlToValidate="txtFinHeight" 
ClientValidationFunction="validateFinHeight"></asp:CustomValidator>

<script type="text/javascript" language="javascript" >
function validateFinHeight(source, arguments)
{
  var ddl = document.getElementById('cboTubeDia');
  var ddlSelIndex = ddl.selectedIndex

  switch(ddlSelIndex)
  {
    case 0:
        arguments.isValid = true;
        return;     
    case 1:
        if(arguments.value%1.25 != 0)
        {
            source.innerText = "Height must be divisibly by 1.25";
            arguments.isValid = false;
            return;
        }
        else
        {
            arguments.isValid = true;
            return;
        }
    case 2:
        if(arguments.value%1.5 != 0)
        {
            source.innerText = "Height must be divisibly by 1.5";
            arguments.isValid = false;
            return;
        }
        else 
        {
            arguments.isValid = true;
            return;
        } 
  }
}
</script>

Answer 1

There were several minor mistakes in your javascript functions according to case sensitivity(f.e. IsValid and Value). I have debugged it to see what property of the Error-Span i must set. It was the textContent attribute for Firefox and innerText for IE.

The working function(cross browser capable):

  function validateFinHeight(source, args) {
        var ddl = document.getElementById('cboTubeDia');
        var ddlSelIndex = ddl.selectedIndex;
        var errorMsg = "";

        switch (ddlSelIndex) {
            case 0:
                args.IsValid = true;
                return;
            case 1:
                if (args.Value % 1.25 != 0) {
                    errorMsg = "Height must be divisibly by 1.25";
                    if (source.innerText) {
                        source.innerText = errorMsg;
                    } else {
                        source.textContent = errorMsg;
                    }
                    args.IsValid = false;
                    return;
                }
                else {
                    args.IsValid = true;
                    return;
                }
            case 2:
                if (args.Value % 1.5 != 0) {
                    errorMsg = "Height must be divisibly by 1.5";
                    if (source.innerText) {
                        source.innerText = errorMsg;
                    } else {
                        source.textContent = errorMsg;
                    }
                    args.IsValid = false;
                    return;
                }
                else {
                    args.IsValid = true;
                    return;
                }
        }
    }

Answer 2

Sorry, can't comment other answers as a guest. I'd like to point out an issue with the Question as well as Tims answer:

Using 'arguments' as a parameter name may lead to trouble (at least I just experienced that in firefox 20) because it is also an auto-variable which contains all arguments that are passed to the function, so there is a name conflict if a parameter is named the same way. I recommend changing the parameter name to 'args' or anything else.