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?

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?

• c#
• javascript
• jquery
• validation

• use java script for calulation on textbox – Krunal Mevada Commented Aug 13, 2012 at 9:33
• Your problem looks similar to the below question [1]: stackoverflow./questions/1524492/… – Santhanam Commented Aug 13, 2012 at 9:41
• No there is no required field validator in my case – PeteEngineer Commented Aug 13, 2012 at 9:45
• Krunal .. that we can do it on least priority...if nothing else works – PeteEngineer Commented Aug 13, 2012 at 9:47
• See Answer from Naveen at stackoverflow./questions/1524492/… ... basically add CausesValidation="true" for the text box, better explained there. – Echeban Commented Feb 18, 2019 at 13:05

4 Answers 4

function txtAmount_TextChanged(){
    //do validations here, Eg: validate if txtAmount is valid amount and "> 0"
   return false; //if somethings's wrong, else true

}

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;
}

Use Input event to check the added text in Textbox using jquery

jQuery('#txtAmount').live('input', function() 
   {
     // do your Validation 
     // If Valid return True
     // If Invalid Return False
   }
) 

you can use jquery change function

$('#txtbox').change(function() { if(validationfail){return false;} );

you can use keychange event also

 $('#txtbox').keyup(function() { 
       if(validationfail){return false;} 
    });