How to copy a selected row in same gridview using asp.net & C#

Before doing split i have two rows already in my datatable & also in gridview.

protected void gvGRNItems_RowCommand(object sender, GridViewCommandEventArgs e)
{if (e.CommandName == "Split")
{
GridViewRow gr = (GridViewRow)((Button)e.CommandSource).Parent.BindingContainer;
if (UpdateGRNItemSplit(Convert.ToInt32(e.CommandArgument), gr))
{
//gvGRNItems.EditIndex = -1;
FillGRNItems();
}
}
}

protected bool UpdateGRNItemSplit(int p, GridViewRow gr)
{
bool bolRetVal = false;

Label lblPOSchID = (Label)gr.FindControl("lblScheduleNo");

DataRow drNew;
drNew = dtGRNItem.NewRow();
DataView dv;
dv = dtGRNItem.DefaultView;
dv.RowFilter = "POScheduleId=" + Convert.ToInt32(lblPOSchID.Text);
DataTable dt = new DataTable();
if (dv.ToTable().Rows.Count > 0)
{
dt = dv.ToTable();
}

foreach(DataRow dr in dt.Rows)
{
drNew["GRNItemID"] = CurrentGRNItemId--;
drNew["GRNID"] = iGRNID;
drNew["Sno"] = dtGRNItem.Rows.Count + 1;
drNew["ItemId"] = dr["ItemId"];
drNew["POID"] = dr["POID"];
drNew["POScheduleId"] = dr["POScheduleId"];
drNew["PONO"] = dr["PONO"];
drNew["PODATE"] = dr["PODATE"];
drNew["Date"] = dr["Date"];
drNew["Qty"] = dr["Qty"];
drNew["OurName"] = dr["OurName"];
dtGRNItem.Rows.Add(drNew);
}


dtGRNItem.AcceptChanges();

bolRetVal = true;

return bolRetVal;
}

private void FillGRNItems()
{
gvGRNItems.ShowFooter = (gvGRNItems.Enabled == true && dtGRNItem.Rows.Count > 0 && gvGRNItems.EditIndex < 0 && txtChallanNo.Enabled);
gvGRNItems.DataSource = dtGRNItem;
gvGRNItems.DataBind();
}

Everything till here works fine...but when i bind the datatable to gridview ,only two rows gets binded , the third row doesnt get binded to gridview.