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.grvFinApproval.ClientID %>');
TotalChkBx = <%=this.grvFinApproval.Rows.Count%>;
alert(TotalChkBx);
Counter = 0;
}
function HeaderClick(CheckBox)
{
var TargetBaseControl = document.getElementById('<%= this.grvFinApproval.ClientID %>');
if(TargetBaseControl!=null) //not working
{
var TargetBaseControl = document.getElementById('<%= this.grvFinApproval.ClientID %>');
var TargetChildControl = "chkFinApproval";
var Inputs = TargetBaseControl.getElementsByTagName("input");
for(var n = 0; n < Inputs.length; ++n)
if(Inputs[n].type == 'checkbox' && Inputs[n].id.indexOf(TargetChildControl,0) >= 0)
Inputs[n].checked = CheckBox.checked;
Counter = CheckBox.checked ? TotalChkBx : 0;
}
}
function ChildClick(CheckBox)
{
var HeaderCheckBox = document.getElementById('<%= this.grvFinApproval.HeaderRow.FindControl("chkCell ").ClientID %>');
if(HeaderCheckBox!=null) //not working
{
if(CheckBox.checked && 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.NullReferenceException: Object reference not set to an instance of an object.

[r035198x]

System.NullReferenceException: 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.getElementById('<%= this.grvFinApproval.HeaderRow.FindControl("chkCell ").ClientID %>');

[r035198x]

Check whether grvFinApproval.HeaderRow.FindControl("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.FindControl("chkCell").Cl ientID will throw a null reference exception.

[vijeberal]

Check whether grvFinApproval.HeaderRow.FindControl("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.FindControl("chkCell").Cl ientID 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