Question

I have a series of textboxes on a form. When the user inserts numbers into these textboxes, calculations are made and <asp:Label> controls are updated via JavaScript to reflect these calculations:

document.getElementById('<%=TotalLoans.ClientID %>').innerHTML = TotalLoans;

This correctly updates the UI. However, when I try to access the value in the codebehind, the Text property is empty. This makes sense I guess, since I was updating the innerHTML property via the JavaScript.

//TotalLoans.Text will always be equal to "" in this scenario
double bTotalLoans = string.IsNullOrEmpty(TotalLoans.Text) 
                   ? 0.00 
                   : Convert.ToDouble(TotalLoans.Text);

How do I update the Text property of the <asp:Label> via JavaScript in such a way that I can read the property in the codebehind?

Update

This is a small problem on a large form that contains 41 labels, each of which displays the results of some calculation for the user. Taking the advice of FishBasketGordo I converted my <asp:Label> to a disabled <asp:TextBox>. I’m setting the value of the new textbox as such:

    document.getElementById('<%=TotalLoans.ClientID %>').value = TotalLoans;

Again, in the codebehind, the value of TotalLoans.Text is always equal to “”.

I don’t mind changing how I approach this, but here’s the crux of the matter.

I am using JavaScript to manipulate the property values of some controls. I need to be able to access these manipulated values from the code behind when ‘Submit’ is clicked.

Any advice how I can go about this?

Update 2

Regarding the answer by @James Johnson, I am not able to retrieve the value using .innerText property as suggested. I have EnableViewState set to true on the <asp:Label>. Is there something else I am missing?

I don’t understand why, when I type in a textbox and submit the form, I can access the value in the codebehind, but when I programmatically change the text of a textbox or label by way of JavaScript, I cannot access the new value.

Answer 1

Place HiddenField Control in your Form.

<asp:HiddenField ID="hidden" runat="server" />

Create a Property in the Form

protected String LabelProperty
{
    get
    {
        return hidden.Value;
    }
    set
    {
        hidden.Value = value;
    }
}

Update the Hidden Field value from JavaScript

<script>
   function UpdateControl() {
            document.getElementById('<%=hidden.ClientID %>').value = '12';
   }
</script>

Now you can access the Property directly across the Postback. The Label Control updated value will be Lost across PostBack in case it is being used directly in code behind .