Question

I have the following text box control ;

   <asp:TextBox ID="txtAmount" runat="server" AutoPostBack="true" Width="85px" class="validate[ERExpenseTypeDaterequired,custom[float]]"
                                OnTextChanged="txtAmount_TextChanged"   ></asp:TextBox>

Here, if there any value change in the text box , txtAmount_TextChanged will be called because AutoPostBack="true" is there in the control.

So if we put a non numeric value in the textbox, validation error will fire from the attribute Class using Jquery, but this error which pops up as a red box from the textbox wont stays for more than 3 seconds, it vanishes when the page posts back within 3 seconds, This post back is happening just because there is a AutopostBack="true".

I cannot do Autopostback="false" because, I need to do some calculation based on this text box value change on the spot.

If I do Autopostback="false", page will not post back and error message stays for ever, but I cannot do any calculations on “txtAmount_TextChanged” event as this event will never be called on textchcange if Autopostback="false".

So, what I do to prevent this postback, if there is any validation error in this textbox?

Answer 1

You’ll need to add a client-side event handler, and return false from it when you don’t want a PostBack to happen.

<asp:TextBox onkeydown="return doMyCheck()" ID="txtAmount" runat="server"
  AutoPostBack="true" Width="85px" class="validate[ERExpenseTypeDaterequired,custom[float]]"
  OnTextChanged="txtAmount_TextChanged"></asp:TextBox>

JavaScript:

function doMyCheck() {
  if (// call your jQuery validity check) 
    return false;
}