Search in Datagridview

Question

I have a datagridview in my project and i have merged two table in that gridview using inner join sql query and now i want to search in that gridview 

 

Code is like ..

 

public void Show_items()
        {
            con.Open();
            SqlDataAdapter sda1 = new SqlDataAdapter("select ITEM.ITEM_NAME, STOCK.QTY, ITEM.SALEPRICE, ITEM.GST, ITEM.TOTALSALEPRICE from ITEM inner join STOCK on ITEM.ITEM_NAME = STOCK.ITEM_NAME ", con);
            DataTable dt1 = new DataTable();
            sda1.Fill(dt1);
            search_item_grid.Rows.Clear();
            foreach (DataRow dr1 in dt1.Rows)
            {
                int n = search_item_grid.Rows.Add();
                search_item_grid.Rows[n].Cells[0].Value = dr1[0].ToString();
                search_item_grid.Rows[n].Cells[1].Value = dr1[1].ToString();
                search_item_grid.Rows[n].Cells[2].Value = dr1[2].ToString();
                search_item_grid.Rows[n].Cells[3].Value = dr1[3].ToString();
                search_item_grid.Rows[n].Cells[4].Value = dr1[4].ToString();
            }
            con.Close();
        }