title: Update value in datatable
body: <p>I was trying to update my datatable when ever the same book title is inserted into the cart. </p>
  
  <pre><code>public bool checkBook(DataTable dt, String title)
  {
      bool returnval = false;
      try
      {
  
          foreach (DataRow dr in dt.Rows)
          {
              String checktitle = dr["Title"].ToString();
              if (title == checktitle)
              {
                  int a = Convert.ToInt32(dr["quantity"].ToString());
                  dr["quantity"] = a + 1;
                  returnval = true;
              }
  
          }
      }
      catch (Exception ex)
      {
          //do something
      }
      return returnval;
  }
  </code></pre>
  
  <p>Initial value in the quantity is 1, but when button was submitted, the quantity is still 1, but when it enter the third time, the number only started to increase by one. I don't understand where is the mistake? </p>
  
  <p>Edited :: </p>
  
  <pre><code>protected void ListView1_SelectedIndexChanged(object sender, EventArgs e)
  {
      String title = ((Label)(ListView1.Items[ListView1.SelectedIndex].FindControl("Title"))).Text; ;
      decimal price = decimal.Parse(((Label)(ListView1.Items[ListView1.SelectedIndex].FindControl("Price"))).Text);
  
      cart cart = new cart(title, price);
  
      if (HttpContext.Current.Session["Cart"] != null)
      {
          DataTable shoppingcart = (DataTable)HttpContext.Current.Session["Cart"];
          bool check = checkBook(shoppingcart, title);
          if (check != true)
          {
              ShoppingCart.DataSource = cart.cartrow(shoppingcart);
              ShoppingCart.DataBind();
          }
          else
          {
              // if is true, it suppose to increase the quantity here 
  
              }
  
          }
      }
  
      else
      {
  
          HttpContext.Current.Session["Cart"] = cart.shoppingCart();
          ShoppingCart.DataSource = cart.shoppingCart();
          ShoppingCart.DataBind();
      }
  
  }
  </code></pre>
  
  <p>class::</p>
  
  <pre><code>String title { get; set; }
  decimal price { get; set; }
  int quantity = 1;
  DataTable CartTable;
  DataRow tableRow;
  public cart(String _title, decimal _price)
  {
  title = _title;
  price = _price;
  }
  public DataTable shoppingCart()
  {
  CartTable = new DataTable("cart");
  
  CartTable.Columns.Add("ID", typeof(Int32));
  CartTable.Columns["ID"].AutoIncrement = true;
  CartTable.Columns["ID"].AutoIncrementSeed = 1;
  
  CartTable.Columns.Add("Title");
  CartTable.Columns.Add("Price");
  CartTable.Columns.Add("quantity");
  CartTable.Columns["quantity"].DataType = typeof(Int32);
  
  tableRow = CartTable.NewRow();
  tableRow["Title"] = title;
  tableRow["Price"] = price;
  tableRow["quantity"] = quantity;
  CartTable.Rows.Add(tableRow);
  return CartTable;
  }
  
  public DataTable cartrow(DataTable _cart)
  {
  
  tableRow = _cart.NewRow();
  tableRow["Title"] = title;
  tableRow["Price"] = price;
  tableRow["quantity"] = quantity;
  _cart.Rows.Add(tableRow);
  return _cart;
  
  }
  </code></pre>