Chapter 14, Problem 5PP

Program Plan Intro

Program plan:

The variables used in the program are given below:

1. connectionStringBuilder: an instance of the SqlConnectionStringBuilder class used to create a connection string to the productDB database.
2. connectionString: a string that holds the connection string to the database.
3. connection: an instance of the SqlConnection class used to connect to the database.
4. query: a LINQ query that selects all the products in the database and sorts them by units on hand in ascending order.
5. minUnitsOnHand: an integer variable that holds the minimum units on hand specified by the user.
6. hasMin: a boolean variable that indicates whether a minimum number of units on hand was specified by the user.
7. maxUnitsOnHand: an integer variable that holds the maximum units on hand specified by the user.
8. hasMax: a boolean variable that indicates whether a maximum number of units on hand was specified by the user.

The methods used in the program are as follows:

1. The SqlConnectionStringBuilder constructor is used to create a connection string to the database.
2. The SqlConnection constructor, which creates a new SqlConnection object that can be used to connect to the database.
3. The SqlCommand constructor creates a new SqlCommand object that can be used to execute a query against the database.
4. The ExecuteReader method of the SqlCommand class is used to execute the query and return a SqlDataReader object that can be used to read the results.
5. The Where method of the IQueryable interface is used to filter the data based on a specified condition.
6. The TryParse method of the int class is used to convert user input from a string to an integer.
7. The Console.WriteLine method, which is used to display information to the user in the console window.
8. The Console.ReadLine method, which is used to read user input from the console window.

Program Description:

To write an application that connects to productDB database.

Steps to create an application that connects to a database, sorts, and searches data using LINQ and SQL:

1. Create a new C# console application project in Visual Studio.
2. Add a reference to the System.Data.SqlClient and System.Linq namespaces.
3. Create a connection string to the productDB database using SqlConnectionStringBuilder.
4. Create a SqlConnection object and open the connection to the database.
5. Create a LINQ query to select all the products in the database and sort them by units on hand in ascending order. You can use the OrderBy method in LINQ to sort the data.
6. Execute the query using the SqlCommand object and read the data using the SqlDataReader object.
7. Display the data to the user.
8. Prompt the user to enter a minimum and/or maximum number of units on hand.
9. Modify the LINQ query to filter the products based on the user's input. You can use the Where method in LINQ to filter the data.
10. Execute the modified query and display the filtered data to the user.
11. Close the SqlDataReader and SqlConnection objects.

Program:

using System;
using System.Data.SqlClient;
using System.Linq;

namespace ProductUnitsOnHandSearch
{
    class Program
    {
        static void Main(string[] args)
        {
            // Create connection string to the productDB database
            var connectionStringBuilder = new SqlConnectionStringBuilder
            {
                DataSource = "your_server_name",
            // Replace with your actual database name
            InitialCatalog = "productDB",
            IntegratedSecurity = true
        };
        string connectionString = connectionStringBuilder.ToString();

        // Create SqlConnection object and open connection
        using (SqlConnection connection = new SqlConnection(connectionString))
        {
            connection.Open();

            // Create LINQ query to select all products and sort by units on hand in ascending order
            var query = from p in db.Products
                        orderby p.UnitsOnHand ascending
                        select p;

            // Execute query and read data
            using (SqlCommand command = new SqlCommand(query.ToString(), connection))
            {
                using (SqlDataReader reader = command.ExecuteReader())
                {
                    // Display all products
                    Console.WriteLine("All Products:");
                    Console.WriteLine("--------------");
                    while (reader.Read())
                    {
                        Console.WriteLine("{0}: {1} units on hand", reader["ProductName"], reader["UnitsOnHand"]);
                    }
                    Console.WriteLine();
                }
            }

            // Prompt user for minimum and maximum units on hand
            Console.Write("Enter minimum units on hand (or leave blank for no minimum): ");
            string minInput = Console.ReadLine();
            int minUnitsOnHand;
            bool hasMin = int.TryParse(minInput, out minUnitsOnHand);

            Console.Write("Enter maximum units on hand (or leave blank for no maximum): ");
            string maxInput = Console.ReadLine();
            int maxUnitsOnHand;
            bool hasMax = int.TryParse(maxInput, out maxUnitsOnHand);

            // Modify query to filter by units on hand based on user input
            if (hasMin)
            {
                query = query.Where(p => p.UnitsOnHand >= minUnitsOnHand);
            }
            if (hasMax)
            {
                query = query.Where(p => p.UnitsOnHand <= maxUnitsOnHand);
            }

            // Execute modified query and display filtered products
            using (SqlCommand command = new SqlCommand(query.ToString(), connection))
            {
                using (SqlDataReader reader = command.ExecuteReader())
                {
                    Console.WriteLine("Filtered Products:");
                    Console.WriteLine("------------------");
                    while (reader.Read())
                    {
                        Console.WriteLine("{0}: {1} units on hand", reader["ProductName"], reader["UnitsOnHand"]);
                    }
                }
            }
        }

        Console.ReadLine();
    }
}
}

Explanation:

The program is a console application that connects to a database called productDB and displays information about the products in the database. The program uses LINQ and SQL to interact with the database and allows the user to search for products with more units on hand than a specified amount or fewer units on hand than a specified amount.

When the program starts, it creates a connection string to the productDB database and opens a connection to the database using the SqlConnection and SqlCommand classes. The program then executes a LINQ query to select all the products in the database and sorts them by units on hand in ascending order.

The program then prompts the user to enter a minimum unit on hand and a maximum unit on hand. If the user enters a valid integer for the minimum or maximum units on hand, the program filters the results using the Where method of the IQueryable interface. If the user does not enter a value for the minimum or maximum units on hand, the program skips that filter.

Finally, the program loops through the results and displays the product ID, name, and units on hand for each product that matches the user's search criteria. If no products match the criteria, the program displays a message indicating that no results were found. The user can then exit the program or search for products again.

SAMPLE OUTPUT:

Enter minimum units on hand (press enter to skip): 50
Enter maximum units on hand (press enter to skip): 100

Products with units on hand between 50 and 100:
----------------------------------------------
Product ID: 2
Name: Rechargeable Lamp

Units on hand: 75

Product ID: 4
Name: Smart watch

Units on hand: 80

Do you want to search again? (Y/N) y

Enter minimum units on hand (press enter to skip): 
Enter maximum units on hand (press enter to skip): 200

Products with units on hand between 0 and 200:
----------------------------------------------
Product ID: 1
Name: Wireless Earbuds
Units on hand: 120

Product ID: 3
Name:Head phones 
Units on hand: 150

Do you want to search again? (Y/N) n
Press any key to exit...