Sample Application Multi Layered Architecture (n-tier): –Graphical User Interface (GUI): Forms, components, controls The Visual Designer in Visual Studio

Sample Application

• Multi Layered Architecture (n-tier):– Graphical User Interface (GUI):

• Forms, components, controls• The Visual Designer in Visual Studio

– Application:• Model• Controllers

– Database

FEN 2012 1UCN Technology: Computer Science

Architecture

• So far we have had our “user interface” 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

FEN 2012 UCN Technology: Computer Science 2

Application

Until now we have focused on the

application layer

Architecture


Application

First, we are going to focus on the UI layer

Banking4 – An existing Project

View Code (Banking4)FEN 2012 UCN Technology: Computer Science 4

Banking4 with GUI (Banking5)

View Code (Banking5)FEN 2012 UCN Technology: Computer Science 5

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.



New Form in VS

Toolbox. Here you find GUI components

Properties. Here you can edit components. For instance give the

form a good name


• 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.


• Now ‘Banking4’ shows in the Solution Explorer in Visual Studio:



• 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’



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) {

}

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 used like any other objects.



• 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.



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"); }}

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 databasewill be some kind of SQLserver.


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 for creating the database and inserting test data can be found here.


The 1- n association from Customer toBankAccount 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 changed

• 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<Customer> Customers//{// get { return customers; }//}

public List<Customer> 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 = @"select * 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.

Exercises

• Make the “Show total bal” button work (some refactoring may be necessary).

• Add some more interesting functionality to the application (you may use some of the methods in the controller).

• Refactor the application, so that the different layers (tiers) become components (.dll).


Documents

Sample Application Multi Layered Architecture (n-tier): –Graphical User Interface (GUI): Forms, components, controls The Visual Designer in Visual Studio