Stop postback after alert by javascript in ASP.NET Code

Question

I have a textbox and a button, on button's clientClick I call javascript function and there is also server side coding.

Problem is, the page gets post back even if I have return False in the javascript.

Here is my javascript function:

function checkALphaNumericFormat(str) {

            //get previous value before editing
            var txtUserId = document.getElementById('<%=txtUserId.ClientID%>');            
            var userId = txtUserId.value;
            var patternAlphaNumeric = /^[A-z0-9]+$/gi;
            var match = userId.match(patternAlphaNumeric);

            //Check Null values
            if (txtUserId.value != null && txtUserId.value != "") {

                //Check for AlphaNumeric values for User Id
                if (match == null) {
                    alert("Please provide valid AlphaNumeric User Id");
                    return false  ;
                }

                return false ;
            }
            else {
                    alert("User Id field should not be null");
                    return false  ;               
            }              
            return false ;
        }

and I am calling this function on my Form as:

<asp:Button runat="server" ID="btnCreate"  CssClass="loginButton" style="margin:0px 0px 1px 30px;" OnClientClick ="return checkALphaNumericFormat(this.value);"  Text="CREATE" />

plz provide the button designer where u r calling the on client click — naval
– naval, Commented Aug 26, 2013 at 6:38
call your method like this OnClientClick="return checkALphaNumericFormat(... — Damith
– Damith, Commented Aug 26, 2013 at 6:49
Thanks guys for the information, I am calling it as <asp:Button runat="server" ID="btnCreate" CssClass="loginButton" style="margin:0px 0px 1px 30px;" OnClientClick ="return checkAlphaNumericFormat(this.value);" Text="CREATE" /> Thanks for your replys. The issue is now solved. — user2126933
– user2126933, Commented Aug 26, 2013 at 7:00

Harish Bhatt · Accepted Answer · 2013-08-26 06:51:09Z

7

Try to call JavaScript function as below:

OnClientClick="if(!validateform()){return false;}

where validateform() should be your java script function. Your java script function should have return = true; at the end of function in successfull execution, like in below function:

function validateform()
{
  var txtSearch = document.getElementById('<%=txtKeywordSearch.ClientID%>')
  if(txtSearch.value == '')
  {
  alert('No Search Creatria Selected!');
  return false;
  }
return true; 
}

Please try and let me know if it works for you.

Thanks, Harish

answered Aug 26, 2013 at 6:51

Harish Bhatt

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2 Comments

user2126933 Over a year ago

Hi Harish, Yes this code also works :) Thanks although we can use return checkAlphaNumericFormat(this.value) as this also works. I have found the bottle, it got stuck at other javascript function. Thanks for your help

Harish Bhatt Over a year ago

welcome user2126933 and thanks to let me know the other way to call the function.

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