C#

private DBConnect connection = new DBConnect();

private DataSet dataSet = new DataSet();

private BindingSource bindingSource = new BindingSource();

private Cart cart = null;

private void addCartBtn_Click(object sender, EventArgs e)
{
    this.cart = new Cart(this.dataSet);
    this.cart.Show();
    foreach(DataGridViewRow row in this.dataGridView1.SelectedRows)
        this.cart.AddProcudt(int.Parse(row.Cells["id"].Value.ToString()));
}

public Cart(DataSet aDataSet)
{
    this.dataSet = aDataSet;
    this.bindingSouce.DataSource = this.dataSet.Tables["Product"];
    this.dataGridView1.DataSource = this.bindingSouce;
    bindingSouce.Filter = "id=0";
} 

this.dataGridView1.DataSource = this.bindingSouce;

public Cart()
{
    InitializeComponent();
    this.dataGridView1.AutoGenerateColumns = false;
    DBConnect con = new DBConnect();
    this.dataSet = con.GetRecord("Product");
    this.bindingSouce.DataSource = this.dataSet.Tables["Product"];
    this.dataGridView1.DataSource = this.bindingSouce;
    bindingSouce.Filter = "id=0";
} 

private DataSet dataSet;
private BindingSource bindingSouce = new BindingSource();
private string purchasedItemId = "";