Создать диаграмму Chart из данных dataGridView

            chart1.Series[0].XValueMember = dataGridViewPurchases.Columns[7].DataPropertyName;
            chart1.Series[0].YValueMembers = dataGridViewPurchases.Columns[6].DataPropertyName;
            chart1.DataSource = dataGridViewPurchases.DataSource;
            chart1.DataBind();

            SQLiteCommand cmd1 = con.CreateCommand();
            cmd1.CommandType = CommandType.Text;
            cmd1.CommandText = "SELECT Purchases.idPurchase, Purchases.chekNumber," +
            " Category.[name], Products.[name], Products.model, Products.serialNumber, Products.price," +
            " Purchases.quantity, Purchases.summa, Products.warranty, Purchases.date, Buyers.[name]" +
            " FROM Purchases, Buyers, Products, Category WHERE" +
            " Products.idCategory = Category.idCategory AND Purchases.idProduct =" +
            " Products.idProduct AND Purchases.idBuyer = Buyers.idBuyer AND Purchases.date between '" + start + "' and '" + finish + "'";
            cmd1.ExecuteNonQuery();
            System.Data.DataTable dt1 = new System.Data.DataTable();
            SQLiteDataAdapter da1 = new SQLiteDataAdapter(cmd1);
            da1.Fill(dt1);
            var category_Data = dt1.AsEnumerable()
                .GroupBy(row => row.Field<string>("name"))
                .Select(cat => new
                {
                    Category_Name = cat.Key,
                    Category_Count = cat.Count()
                });
            foreach (var c in category_Data)
            {
                chart1.Series["Категория"].Points.AddXY(c.Category_Name, c.Category_Count);
            }