asked on

Cannot call C# function on closing Asp.net web page

Hi

I get the following error "Microsoft JScript runtime error: 'null' is null or not an object"
at this line btn.click(btnHidden_Click) when running the code below ;

I just need some way of calling a server C# function to dispose a few variables
when a user closes the form. I think the issue is with the master form however
all variations of document.getElementById('btnHidden'); thatI've tried doesnt seam
to work

Any assistance would be appreciated

Kind regards
Nick

Asp.net 2008 Aspx
<%@ Page Theme="MainTheme" Language="C#" MasterPageFile="~/Yyyyyy.Master" . . . . .
. . . . . . . . . . . .. . . .. . . ..
<asp:Content ID="Content1" ContentPlaceHolderID="cphTitle" runat="server" >
</asp:Content>

<asp:Content ID="Content2" ContentPlaceHolderID="cphBody" runat="server" >

<script type="text/javascript">

window.onunload = ReleaseVariables()

function ReleaseVariables ()

{
var btn = document.getElementById('btnHidden');

btn.click(btnHidden_Click);

}

</script>

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">

. . . . . . . .

</table>

<asp:Label ID="Label1" runat="server" Text=""></asp:Label>

<input type="button" id="btnHidden" value="button" onclick=btnHidden_Click/>

</asp:Content>

c# code behind
protected void btnHidden_Click(object sender, EventArgs e)
{
if (dv != null) dv.Dispose();
if (dv2 != null) dv2.Dispose();
}

ASKER CERTIFIED SOLUTION

Jesse Houwing

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Nick_011

ASKER

Thanks for the Info.

After looking at my source code again, I cant understand why the session variables arn't
preserving the dataview variables. It used to work before the dataview variables were
disposed

OraAdapter = new OracleDataAdapter(OraCommand);
OraDataset = new DataSet();
OraDataset.Clear();
OraAdapter.Fill(OraDataset);
// set some gridview properties
GridView1.AllowPaging = true;
GridView1.PageSize = 14;
// bind dataset to grid
GridView1.DataSourceID = null;
dv = OraDataset.Tables[0].AsDataView();
Session["dataView"] = dv;
GridView1.DataSource = dv;
GridView1.DataBind();

protected void GridView1_PageIndexChanging(object sender,
GridViewPageEventArgs e)
{
// get dataview from session
dv = (DataView)Session["dataView"];
GridView1.DataSource = dv;
GridView1.PageIndex = e.NewPageIndex;
GridView1.DataBind(); // re-bind data
/*if (dv != null)
{
dv.Dispose();
dv = null;
}*/
}

public void bindGridView(string sortExp, string sortDir)
{
dv = (DataView)Session["dataView"];
GridView1.DataSource = dv;

if (sortExp != string.Empty)
{
dv.Sort = string.Format("{0} {1}", sortExp, sortDir);
}
GridView1.DataSource = dv;
GridView1.DataBind();
/*if (dv != null)
{
dv.Dispose();
dv = null;
}*/
}

Jesse Houwing

You're not storing a copy of the object in the session, but only a reference to it. As soon as you call Dispose on the DataView, it is also disposed inside the Session collection.

Nick_011

ASKER

Thanks that does explain the situation.