protected void btnSave_Click(object sender, EventArgs e)
{
Session["Layout"] = ASPxPivotGrid1.SaveLayoutToString(PivotGridWebOptionsLayout.DefaultLayout);
MemoryStream collapseStateStream = (MemoryStream)(Session["CollapseStateStream"]);
if (collapseStateStream != null)
{
collapseStateStream.Dispose();
}
collapseStateStream = new MemoryStream();
ASPxPivotGrid1.SaveCollapsedStateToStream(collapseStateStream);
Session["CollapseStateStream"] = collapseStateStream;
}