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troubleshooting Question

Javascript asynchronous call help

Avatar of claracruz
claracruz asked on
9 Comments1 Solution948 ViewsLast Modified:
Hello  Experts,

I am using the following  site as a guide to implementing Ajax in my website;- http://www.ajaxpro.info/quickguide.aspx

I have done the following;-

On my usercontrol page I have the following javascript;-

<script type="text/javascript">
function calculateCurrency()
   Controls_CurrencyConverter.CalculateCurrency(calculateCurrency_callback); // asynchronous call

// This method will be called after the method has been executed
// and the result has been sent to the client.

function calculateCurrency_callback(res)
  theForm.lblResult2.value = res.value;

there is by label control and my image button;-
<input type="text" id="lblResult2" maxlength="5px" readonly="readonly" style="width:70px;" />
<img id="btnSubmit" alt="Submit" src="../images/button_convert.gif" onclick="calculateCurrency();"/>  

and in the codebehind of my user control I have the following;-

    public string CalculateCurrency()
            DataSet ds = new DataSet();
            DataRow[] rows = ds.Tables[0].Select("Currency = '" + ddlConverter.SelectedItem.Text + "'");

            decimal CurrencyAmount = Convert.ToDecimal(txtCurAmount.Text);
            decimal rate = Convert.ToDecimal(rows[0]["Exchange"]);
            decimal amount = CurrencyAmount * rate;
            return amount.ToString("f2");
        catch (FormatException)
            return "Error";

However, when I click submit "null" is returned rather than the correct value. what am I doing wrong?

PS: It works fine if  I replace the HTML image button with an asp.net control and call it normally with the "protected void ImageButton1_Click(object sender, ImageClickEventArgs e)"
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