Adding value after retrieving from database

Question

In my windows application, I have price column in the database which stores the value of the product.

In my winform I have one combo box and list box. Combo box displays all the items in the database. When user selects product from the combo box and click add, these product will be added to the list box.

In mean time when user clicks add item, I retrieve the price of the item and pass it to method which add this value.

But how can I add the multiple values, for example I add product 1, product 2 from combo box to list box, I want to add the value those items as 550+200 = 750 and display it to the text box.

Currently I am doing this.

To retrieve price:

public DataSet searchforPrice(string price)
        {
            DataSet dataSet = new DataSet();

            // Create connection object
            OleDbConnection oleConn = new OleDbConnection(connString);
            try
            {
                oleConn.Open();
                string sql = "SELECT [Price]  FROM [Product] WHERE [Product Name] ='" + price + "'";
                OleDbDataAdapter dataAdapter = new OleDbDataAdapter(sql, oleConn);
                dataAdapter.Fill(dataSet, "Product");

            }
            catch (Exception ex)
            {
                Console.WriteLine(ex.ToString());
            }
            finally
            {
                oleConn.Close();
            }
            return dataSet;

  }

Adding item to listbox and display total price:

private void button2_Click(object sender, EventArgs e)
        {
            listBox1.Items.Add(comboBox2.Text);
            maskedTextBox10.Text = addPrice().ToString();

        }

Adding price of the product which is being selected in combobox

public int addPrice()
    {
        DataSet ds = searchforPrice(comboBox2.Text);
        int price =  Convert.ToInt32(ds.Tables[0].Rows[0]["Price"]);
        return price;

    }

Your code here is in need of some work. First, look into the "using" statement, it will help you not need to explicitly use the try/finally. Your parameter to the method is named "price," but it is filtering against a database field called "Product Name." You should rename that parameter. You also want to consider using parameterized queries to protect against any special characters and SQL Injection vulnerabilities. Your method names start in lower case, C# coding conventions suggest that method names be PascalCased, unlike Java's camelCased convention. — Anthony Pegram

Marius Bancila Marius Bancila · Accepted Answer · 2013-02-17T06:09:35

The argument for your searchforPrice method should rather be called product than price.

Now, you're addPrice method is wrong, because it doesn't add any price. It just returns the price of the currently selected item in the combo. It should probably look like this:

public int addPrice()
{
    DataSet ds = searchforPrice(comboBox2.Text);
    int sum = Convert.ToInt32(maskedTextBox10.Text);
    int price =  Convert.ToInt32(ds.Tables[0].Rows[0]["Price"]);
    return sum + price;
}

Of course, if you delete items, you should do something similar.

IMO, rather than applying this logic, you should store the price of each item in the list, and display in the textbox the sum of those prices. If you remove items, it would be easier (and more correct) to recompute the sum.

Adding value after retrieving from database

1 Answers