Architecture Multi Layered Architecture (n-tier): Application: Model Controllers Database Access Graphical User Interface (GUI): Forms, components, controls The Visual Designer in Visual Studio

Architecture So far we have had our “user interface” and “database” in the Main method This won’t do with reel users! Normally one will use what is known as a layered (or n tier) architecture, for instance: UI Controller Model Database Application Until now we have focused on the application layer

Architecture Application In this session we are going to focus on the Data Access layer

Banking4 View Code (Banking4View Code (Banking4)

Banking4 with GUI (Banking5) View Code (Banking5)

How to Create a GUI for an Existing Project Firstly you must have a working project with model and controller, for instance Banking4. First step is to create a new solution in Visual Studio: It must be a “Windows Form Application” Give it a good name. And choose a location for it.

How to Create a GUI for an Existing Project New Form in VS Toolbox. Here you find GUI components Properties. Here you can edit components. For instance give the form a good name

How to Create a GUI for an Existing Project Right click on the solution. Choose ‘Add’ and ‘Existing Project’. Locate the project you want to add the GUI to: Here is the project file for ‘Banking4’ Choose that.

How to Create a GUI for an Existing Project Now ‘Banking4’ shows in the Solution Explorer in Visual Studio:

How to Create a GUI for an Existing Project Next we want to make the project (‘Banking4’) known to our GUI project: You must use the namespace of Banking4: Right click on the form and choose ‘View Code’ Type this using: But the compiler doesn’t recognises it? Right click on ‘References’ for the GUI project in the Solution Explorer and choose ‘Add Reference’

How to Create a GUI for an Existing Project Choose the project tab. Choose the project you want – Banking4...and ‘OK’ Now the compiler recognises ‘Banking4’ namespace and we are ready.

Using the Existing Project Right click on the form, choose ‘View Code’, and now we can write code, for instance get an instance of the controller: namespace Bank4WithGUI { public partial class Form1 : Form { private BankCtr myBank = BankCtr.GetInstance(); public Form1() { InitializeComponent(); } Now myBank can be used in the form, and we are able to communicate with the Banking4 application.

Adding Components and Controls to the Form Drag- and-drop. Label ToolStrip TextBox Button You may change the properties of components

Adding Code Test data is added by the constructor. New method added by me. //--- public Form1() //Constructor { CreateTestData();//my method InitializeComponent(); } //--- private void CreateTestData() { Customer c = new Customer(1, "Peter Thomsen"); myBank.AddCustomer(c); myBank.AddCustomer(new Customer(2, "Ib Helmer")); BankAccount acc1 = new BankAccount(1, 8, 100); BankAccount acc2 = new BankAccount(2, 0.25, 0); BankAccount acc3 = new BankAccount(3, 5, 1000); c = myBank.GetCustomer(1); c.AddAccount(acc1); c.AddAccount(acc2); c.AddAccount(acc3); c = myBank.GetCustomer(2); c.AddAccount(acc2); }

Getting some Action Double click on the Find Customer Button and you get an empty event handler method for the button. This method is executed when the button is clicked. Type in the code for the actions that you want. //--- private void button1_Click(object sender, EventArgs e) { } { string input = this.textBox1.Text; int custNo = Convert.ToInt32(input); //no error handling Customer c = myBank.GetCustomer(custNo); this.textBox2.Text = c.Name; }

Getting some Action Components are objects and may be used like any other objects. private void button1_Click(object sender, EventArgs e) { string input = this.textBox1.Text; int custNo = Convert.ToInt32(input); //no error handling Customer c = myBank.GetCustomer(custNo); this.textBox2.Text = c.Name; } Use ‘this’ and the IntelliSense to find variable names of components and properties of components.

Error Handling - Exceptions If, what is entered here, not is a valid and existing customer number; some exception (NumberFormat or NullPointer) will make the program crash. private void button1_Click(object sender, EventArgs e) { string input = this.textBox1.Text; int custNo = Convert.ToInt32(input); //no error handling Customer c = myBank.GetCustomer(custNo); this.textBox2.Text = c.Name; }

Error Handling - Exceptions We want to catch and handle that exception. That is done by enclosing the code in a try-block. After that we have a catch-block where we handle the exception. private void button1_Click(object sender, EventArgs e) { string inString = textBox1.Text; try { int custNo = Convert.ToInt32(inString); c = bankCtr.GetCustomer(custNo); textBox2.Text = c.Name; } catch (Exception excep) { MessageBox.Show("Customer number must be an integer"); } Investigate Banking5

Adding a Database So far we have create some test data and kept them in memory. This won’t do for real application! Normally one will use what is known as a layered (or n tier) architecture, for instance: UI Controller Model Database And the database will be some SQL server. Application Now we focus on adding a database

A Side: Creating the Database First we define our database tables (this is done using SQL Server Management Studio, but can also be done from Visual Studio (not Express): One table per domain object: Customer (Bank)Account View the database in SQL Server Management Studio SQL scripts SQL scripts for creating the database and inserting test data can be found here. The 1- n association from Customer to BankAccount is implemented in the database by including custNo as a foreign key in Account

Adding a Database - Architecture We will add a database to the Banking Project. Architecture: The Controller is responsible for communication with the database connection classes (DBLayer). The DBLayer encapsulates the code for accessing the database and stores and builds objects. The DBLayer takes the role of containers. View Code SQL Server

Architecture – in Visual Studio One Solution – 5 projects, each project having its own namespace. Architecture: Model: (old Banking4). The controller is put in its own project: Controller. Banking5 is the old GUI. The DBLayer has classes for accessing the database and storing and building objects. BankingWithFullMonty is the main project with the new start-up form

DBLayer We use a SQL Server Database. The Class AccessDbSQLClient is responsible for opening and closing the connection and for creating a Command object that can be passed to the SQL Server. The class CustomerDBSQLClient is responsible for retrieving and storing Customer objects in the database. View Code

The Controller Old implementation using lists is change Instead we use calls to the database. //public void AddCustomer(Customer c) //{ // customers.Add(c); //} public void AddCustomer(Customer c) { CustomerDBSQLClient.CreateCustomer(c.CustNo, c.Name); } //public List Customers //{ // get { return customers; } //} public List Customers { get { return CustomerDBSQLClient.GetCustomers(); } }

The Controller Complex search loops are replaced by calls to the database. //public Customer GetCustomer(int no) //{ // //if customer not found, null is returned // Customer c = null; // int i = 0; // bool found = false; // while (!found && i < customers.Count) // { // c = customers[i]; // if (c.CustNo == no) // found = true; // else // i++; // } // return c; //} public Customer GetCustomer(int no) { return CustomerDBSQLClient.FindCustomerByNo(no); }

class CustomerDBSQLClient public static Customer FindCustomerByNo(int custNo) { string sql * from Customer where custNo = " +custNo; dbCmd = AccessDbSQLClient.GetDbCommand(sql); IDataReader dbReader; dbReader = dbCmd.ExecuteReader(); Customer c; if (dbReader.Read()) c = new Customer(Convert.ToInt32(dbReader["custNo"].ToString()), dbReader["name"].ToString()); else c = null; dbReader.Close(); AccessDbSQLClient.Close(); return c; } The SQL Statement is build Command object with this SQL statement is build The command is sent to the SQL Server and executed The result is returned in a reader object – The Customer object is build from the reader DB Connection is closed Eventually the Customer object is returned.