Javascript error on empty GridView

[vijeberal]

Hi all,
I am working on a GridView and there exist a Checkbox control .. iplaced another checkbox in header also i have written a javascript for selection of checkboxex fro e.g if you click on header checkbox that script will select all the child checkboxes its working fine but when that gridview doesn,t contain anything at that time this script is throwing an error i am sending the code also immidiately help needed
window.onload = function()
{
var gridv=document. getElementById( '<%= this.grvFinAppr oval.ClientID %>');
TotalChkBx = <%=this.grvFinA pproval.Rows.Co unt%>;
alert(TotalChkB x);
Counter = 0;
}
function HeaderClick(Che ckBox)
{
var TargetBaseContr ol = document.getEle mentById('<%= this.grvFinAppr oval.ClientID %>');
if(TargetBaseCo ntrol!=null) //not working
{
var TargetBaseContr ol = document.getEle mentById('<%= this.grvFinAppr oval.ClientID %>');
var TargetChildCont rol = "chkFinApproval ";
var Inputs = TargetBaseContr ol.getElementsB yTagName("input ");
for(var n = 0; n < Inputs.length; ++n)
if(Inputs[n].type == 'checkbox' && Inputs[n].id.indexOf(Tar getChildControl ,0) >= 0)
Inputs[n].checked = CheckBox.checke d;
Counter = CheckBox.checke d ? TotalChkBx : 0;
}
}
function ChildClick(Chec kBox)
{
var HeaderCheckBox = document.getEle mentById('<%= this.grvFinAppr oval.HeaderRow. FindControl("ch kCell").ClientI D %>');
if(HeaderCheckB ox!=null) //not working
{
if(CheckBox.che cked && Counter < TotalChkBx)
Counter++;
else if(Counter > 0)
Counter--;
if(Counter < TotalChkBx)
HeaderCheckBox. checked = false;
else if(Counter == TotalChkBx)
HeaderCheckBox. checked = true;
}

}

[r035198x]

What is the error message that you get?

[vijeberal]

What is the error message that you get?

System.NullRefe renceException: Object reference not set to an instance of an object.

[r035198x]

System.NullRefe renceException: Object reference not set to an instance of an object.

Can you try to get the line (number) where that exception is thrown from?

[vijeberal]

Can you try to get the line (number) where that exception is thrown from?

This is the line in Child_CLick
var HeaderCheckBox = document.getEle mentById('<%= this.grvFinAppr oval.HeaderRow. FindControl("ch kCell").ClientI D %>');

[r035198x]

Check whether grvFinApproval. HeaderRow.FindC ontrol("chkCell ") is not null by a simple

if(grvFinApproval.HeaderRow.FindControl("chkCell") == null) {
//output something here to indicate that it's null
}

If you get some output from the if then it explains why
grvFinApproval. HeaderRow.FindC ontrol("chkCell ").ClientID will throw a null reference exception.

[vijeberal]

Check whether grvFinApproval. HeaderRow.FindC ontrol("chkCell ") is not null by a simple

if(grvFinApproval.HeaderRow.FindControl("chkCell") == null) {
//output something here to indicate that it's null
}

If you get some output from the if then it explains why
grvFinApproval. HeaderRow.FindC ontrol("chkCell ").ClientID will throw a null reference exception.

If we dont show the gridview still this script searching for that checkbox...How do i prevent this searching initiated by javascript