When filling datatable, if there are same column name in the datasource then it will add numbers to that.
You can change the gridview header in the Databound event
protected void Gridview2_DataBound(object sender, EventArgs e)
{
foreach (TableCell cl in Gridview2.HeaderRow.Cells)
{
if (cl.Text.StartsWith("SNo"))
cl.Text = "SNo";
if (cl.Text.StartsWith("RoomNo"))
cl.Text = "RoomNo";
}
}