Microsoft SQL/Server Databases: Introduction to Client/Server Applications

	Microsoft SQL/Server Databases: Introduction to Client/Server Applications

Introduction

A client/server application is a computer program that allows a user to access something that is stored in a server. Of course, both computers can be workstations and can run the same type of operating system. In most networking environments, the server holds a database and users must access that database from their workstations.

If you want to create a client/server database application, you have many choices among Microsoft Access, XML, file processing, MySQL, Oracle, etc. One more common choice you have is Microsoft SQL Server.

Creating the Database

In a typical client/server database, probably the first thing to do is to create the database. As always, you have many choices. In fact, you can even start with something other than the database.

To launch the server, from the computer where you have installed Microsoft SQL Server or from a workstation where you would have installed the client tools, start Microsoft SQL Server (Start -> All Programs -> Microsoft SQL Server 2008 -> SQL Server Management Studio). On the Standard toolbar, click the New Query button .

Practical Learning: Creating the Database on the Server

On the server, to launch Microsoft SQL Server, click Start -> All Programs -> Microsoft SQL Server 2008 -> SQL Server Management Studio
On the Standard toolbar, click the New Query button

To set code for a simple database, type the following code:

USE master;
GO
CREATE DATABASE Exercise1;
GO
USE Exercise1;
GO
CREATE SCHEMA Management;
GO
CREATE SCHEMA Personnel;
GO
CREATE TABLE Management.Departments
(
	DeptCode nchar(5) not null,
	Department nvarchar(40),
	CONSTRAINT PK_Departments PRIMARY KEY(DeptCode)
);
GO
CREATE TABLE Personnel.Employees
(
	EmplNbr nchar(5) not null,
	FirstName nvarchar(24),
	LastName nvarchar(24) not null,
	DeptCode nchar(5)
		CONSTRAINT FK_Departments
		FOREIGN KEY REFERENCES Management.Departments(DeptCode),
	Title nvarchar(50),
	CONSTRAINT PK_Employees PRIMARY KEY(EmplNbr)
);
GO

To create the database, press F5

Creating the Graphical Application

To allow users to access a database that is stored in a server, you have various options. One is to use a computer language such as C#, Visual Basic, or F#, etc, to create a graphical application. Probably the easiest way to create a graphical application that accesses a Microsoft SQL Server database is to use an integrated development environment (IDE) such as Microsoft Visual Studio (Professional, Ultimate, or one of the free Express editions). Another cheap way is to compile the application from the Command Prompt, in which case you may not have to worry about distributing the application: you can just run the appropriate script on each client workstation.

Let's assume that you are running a Microsoft Windows operating sytem (XP Professional, Vista Professional or Ultimate, or 7 Professional or Ultimate) on the client workstation. First, open Windows Explorer and check the version of the .NET Framework the computer is using. Here is an example:

Practical Learning: Creating a GUI Application Using an IDE

If you have a programming environment such as Microsoft Visual Studio (Professional, Ultimate, or Express), launch it
On the main menu, click File -> New Project...
In the left list, select your language and select Windows Forms Application
Set the Name to Exercise 1
Click OK
On the main menu, click Project -> Add Windows Form...
Set the Name to Departments
Click Add

Design the form as follows:

Control	(Name)	Text
DataGridView	dgvDepartments
GroupBox		New Department
Label		Department Code:
TextBox	txtDepartmentCode
Label		Department:
TextBox	txtDepartment
Button	btnAdd	Add
Button	Close	btnClose

Double-click an unoccupied area of the form, such as on the left side of Close
Return to the form and double-click the Add button
Return to the form and double-click the Close button

Change the file as follows:

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Windows.Forms;
using System.Data.SqlClient;

namespace Exercise1
{
    public partial class Departments : Form
    {
        string serverName;

        public Departments()
        {
            InitializeComponent();
        }

        private void ShowDepartments()
        {
            using (SqlConnection cntExercise =
                new SqlConnection("Data Source=" + serverName + 
                    ";Database='Exercise1';Integrated Security=yes;"))
            {
                SqlCommand cmdDepartments =
                new SqlCommand("SELECT ALL * FROM Management.Departments;",
                	       cntExercise);

                SqlDataAdapter odaDepartments =
                	new SqlDataAdapter(cmdDepartments);
                DataSet dsDepartments = new DataSet("DepartmentsSet");

                cntExercise.Open();

                odaDepartments.Fill(dsDepartments);
                dgvDepartments.DataSource = dsDepartments.Tables[0];
            }
        }

        private void Departments_Load(object sender, EventArgs e)
        {
            // Replace EXPRESSION with the name of the computer
            // on which Microsoft SQL Server is installed
            serverName = "EXPRESSION";
            ShowDepartments();
        }

        private void btnAdd_Click(object sender, EventArgs e)
        {
            if (string.IsNullOrEmpty(txtDepartmentCode.Text))
            {
                MessageBox.Show("You must enter a department code.",
                                "Exercise", MessageBoxButtons.OK,
                                MessageBoxIcon.Information);
                return;
            }

            if (string.IsNullOrEmpty(txtDepartment.Text))
            {
                MessageBox.Show("You must enter the name of a department.",
                                "Exercise", MessageBoxButtons.OK,
                                MessageBoxIcon.Information);
                return;
            }

            using (SqlConnection cntExercise =
               new SqlConnection("Data Source=" + serverName +
                   ";Database='Exercise1';Integrated Security=yes;"))
            {
                SqlCommand cmdDepartments =
                new SqlCommand("INSERT INTO Management.Departments VALUES(" +
                               "'" + txtDepartmentCode.Text + "', '" +
                               txtDepartment.Text + "');",
                               cntExercise);

                cntExercise.Open();
                cmdDepartments.ExecuteNonQuery();

                txtDepartmentCode.Text = "";
                txtDepartment.Text = "";
            }

            ShowDepartments();
        }

        private void btnClose_Click(object sender, EventArgs e)
        {
            Close();
        }
    }
}

On the main menu, click Project -> Add Windows Form...
Set the Name to Employees
Click Add

Design the form as follows:

Control	(Name)	Text
DataGridView	dgvEmployees
GroupBox		New Employee
Label		Employee #:
MaskedTextBox	txtEmployeeNumber
Label		First Name:
TextBox	txtFirstName
Label		Last Name:
TextBox	txtLastName
Label		Department:
ComboBox	cbxDepartments
Label		Title:
TextBox	txtTitle
Button	btnAdd	Add
Button	Close	btnClose

Double-click an unoccupied area of the form, such as on the left side of Close
Return to the form and double-click the Add button
Return to the form and double-click the Close button

Change the file as follows:

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Windows.Forms;
using System.Data.SqlClient;

namespace Exercise1
{
    public partial class Employees : Form
    {
        string serverName;

        public Employees()
        {
            InitializeComponent();
        }

        private void ShowEmployees()
        {
            using (SqlConnection cntExercise =
                new SqlConnection("Data Source=" + serverName +
                    ";Database='Exercise1';Integrated Security=yes;"))
            {
                SqlCommand cmdEmployees =
                new SqlCommand("SELECT ALL * FROM Personnel.Employees;",
                	       cntExercise);

                SqlDataAdapter odaEmployees = new SqlDataAdapter(cmdEmployees);
                DataSet dsEmployees = new DataSet("EmployeesSet");

                cntExercise.Open();

                odaEmployees.Fill(dsEmployees);
                dgvEmployees.DataSource = dsEmployees.Tables[0];
            }
        }

        private void Employees_Load(object sender, EventArgs e)
        {
            // Replace EXPRESSION with the name of the computer
            // on which Microsoft SQL Server is installed
            serverName = "EXPRESSION";
            ShowEmployees();

            using (SqlConnection cntExercise =
                new SqlConnection("Data Source=" + serverName +
                    ";Database='Exercise1';Integrated Security=yes;"))
            {
                SqlCommand cmdDepartments =
                new SqlCommand("SELECT ALL * FROM Management.Departments;",
                	       cntExercise);

                cntExercise.Open();
                SqlDataReader rdrDepartment = cmdDepartments.ExecuteReader();

                while(rdrDepartment.Read())
                    cbxDepartments.Items.Add(rdrDepartment.GetString(0) +
                    			     " - " + rdrDepartment.GetString(1));
            }
        }

        private void btnAdd_Click(object sender, EventArgs e)
        {
            if (string.IsNullOrEmpty( txtEmployeeNumber.Text))
            {
                MessageBox.Show("You must enter an employee number.",
                                "Exercise", MessageBoxButtons.OK,
                                MessageBoxIcon.Information);
                return;
            }

            if (string.IsNullOrEmpty(txtLastName.Text))
            {
                MessageBox.Show("You must enter thelast name of the employee.",
                                "Exercise", MessageBoxButtons.OK,
                                MessageBoxIcon.Information);
                return;
            }

            using (SqlConnection cntExercise =
               new SqlConnection("Data Source=" + serverName +
                   ";Database='Exercise1';Integrated Security=yes;"))
            {
                SqlCommand cmdDepartments =
                new SqlCommand("INSERT INTO Personnel.Employees VALUES(" +
                               "'" + txtEmployeeNumber.Text + "', '" +
                               txtFirstName.Text + "', '" +
                               txtLastName.Text + "', '" +
                               cbxDepartments.Text.Substring(0, 5) + "', '" +
                               txtTitle.Text + "');",
                               cntExercise);

                cntExercise.Open();
                cmdDepartments.ExecuteNonQuery();

                txtEmployeeNumber.Text = "";
                txtFirstName.Text = "";
                txtLastName.Text = "";
                cbxDepartments.Text = "";
                txtTitle.Text = "";
            }

            ShowEmployees();
        }

        private void btnClose_Click(object sender, EventArgs e)
        {
            Close();
        }
    }
}

In the Solution Explorer, right-click Form1.cs and click Rename
Type Exercise.cs and press Enter twice

Design the form as follows:

Control	(Name)	Text
Button	btnDepartments	Departments...
Button	btnEmployees	Employees...
Button	Close	btnClose

Double-click the Departments button
Return to the form and double-click Departments
Return to the form and double-click Employees

Implement the events as follows:

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Windows.Forms;

namespace Exercise1
{
    public partial class Exercise : Form
    {
        public Exercise()
        {
            InitializeComponent();
        }

        private void btnDepartments_Click(object sender, EventArgs e)
        {
            Departments depts = new Departments();
            depts.Show();
        }

        private void btnEmployees_Click(object sender, EventArgs e)
        {
            Employees empls = new Employees();
            empls.Show();
        }

        private void btnClose_Click(object sender, EventArgs e)
        {
            Close();
        }
    }
}

To execute the application, on the main menu, click Debug -> Start Without Debugging

Practical Learning: Creating a GUI Application Using a Text Editor

Start Notepad

Type the following code:

using System;
using System.Data;
using System.Drawing;
using System.Windows.Forms;
using System.Data.SqlClient;

public class Departments : Form
{
    private string serverName;

    private DataGridView dgvDepartments;
    private Label        lblDepartmentCode;
    private TextBox      txtDepartmentCode;
    private Label        lblDepartment;
    private TextBox      txtDepartment;
    private Button       btnAdd;
    private GroupBox     gbxNewDepartment;
    private Button       btnClose;

    public Departments()
    {
        InitializeComponent();
    }

    private void InitializeComponent()
    {
        dgvDepartments = new DataGridView();
        dgvDepartments.TabIndex = 1;
        dgvDepartments.Size = new System.Drawing.Size(268, 145);
        dgvDepartments.Location = new System.Drawing.Point(12, 12);
        dgvDepartments.ColumnHeadersHeightSizeMode = DataGridViewColumnHeadersHeightSizeMode.AutoSize;

        lblDepartmentCode = new Label();
        lblDepartmentCode.TabIndex = 1;
        lblDepartmentCode.AutoSize = true;
        lblDepartmentCode.Text = "Department Code:";
        lblDepartmentCode.Size = new System.Drawing.Size(93, 13);
        lblDepartmentCode.Location = new System.Drawing.Point(15, 27);

        txtDepartmentCode = new TextBox();
        txtDepartmentCode.TabIndex = 2;
        txtDepartmentCode.Size = new System.Drawing.Size(68, 20);
        txtDepartmentCode.Location = new System.Drawing.Point(114, 24);

        lblDepartment = new Label();
        lblDepartment.TabIndex = 3;
        lblDepartment.AutoSize = true;
        lblDepartment.Text = "Department:";
        lblDepartment.Size = new System.Drawing.Size(65, 13);
        lblDepartment.Location = new System.Drawing.Point(15, 53);

        txtDepartment = new TextBox();
        txtDepartment.TabIndex = 4;
        txtDepartment.Size = new System.Drawing.Size(141, 20);
        txtDepartment.Location = new System.Drawing.Point(114, 50);

        btnAdd = new Button();
        btnAdd.Text = "Add";
        btnAdd.TabIndex = 5;
        btnAdd.Location = new System.Drawing.Point(180, 85);
        btnAdd.Size = new System.Drawing.Size(75, 23);
        btnAdd.UseVisualStyleBackColor = true;
        btnAdd.Click += new System.EventHandler(this.btnAddClick);

        gbxNewDepartment = new GroupBox();
        gbxNewDepartment.Text = "New Department";
        gbxNewDepartment.Size = new System.Drawing.Size(268, 124);
        gbxNewDepartment.Location = new System.Drawing.Point(12, 168);

        gbxNewDepartment.Controls.Add(this.btnAdd);
        gbxNewDepartment.Controls.Add(this.txtDepartment);
        gbxNewDepartment.Controls.Add(this.lblDepartment);
        gbxNewDepartment.Controls.Add(this.txtDepartmentCode);
        gbxNewDepartment.Controls.Add(this.lblDepartmentCode);

        btnClose = new Button();
        btnClose.TabIndex = 3;
        btnClose.Text = "Close";
        btnClose.Size = new System.Drawing.Size(75, 23);
        btnClose.Location = new System.Drawing.Point(192, 304);
        btnClose.UseVisualStyleBackColor = true;
        btnClose.Click += new System.EventHandler(this.btnCloseClick);

        AutoScaleDimensions = new System.Drawing.SizeF(6F, 13F);
        AutoScaleMode = AutoScaleMode.Font;
        ClientSize = new System.Drawing.Size(292, 337);

        Controls.Add(this.dgvDepartments);
        Controls.Add(this.gbxNewDepartment);
        Controls.Add(this.btnClose);
        StartPosition = FormStartPosition.CenterScreen;
        Text = "Departments";
        Load += new System.EventHandler(this.DepartmentsLoad);
    }

    private void ShowDepartments()
    {
        using (SqlConnection cntExercise =
                new SqlConnection("Data Source=" + serverName + 
                    ";Database='Exercise1';Integrated Security=yes;"))
        {
            SqlCommand cmdDepartments =
                new SqlCommand("SELECT ALL * FROM Management.Departments;", cntExercise);

            SqlDataAdapter odaDepartments = new SqlDataAdapter(cmdDepartments);
            DataSet dsDepartments = new DataSet("DepartmentsSet");

            cntExercise.Open();

            odaDepartments.Fill(dsDepartments);
            dgvDepartments.DataSource = dsDepartments.Tables[0];
        }
    }

    private void DepartmentsLoad(object sender, EventArgs e)
    {
        // Replace EXPRESSION with the name of the computer
        // on which Microsoft SQL Server is installed
        serverName = "EXPRESSION";
        ShowDepartments();
    }

    private void btnAddClick(object sender, EventArgs e)
    {
        if (string.IsNullOrEmpty(txtDepartmentCode.Text))
        {
            MessageBox.Show("You must enter a department code.",
                            "Exercise", MessageBoxButtons.OK,
                            MessageBoxIcon.Information);
            return;
        }

        if (string.IsNullOrEmpty(txtDepartment.Text))
        {
            MessageBox.Show("You must enter the name of a department.",
                            "Exercise", MessageBoxButtons.OK,
                            MessageBoxIcon.Information);
            return;
        }

        using (SqlConnection cntExercise =
               new SqlConnection("Data Source=" + serverName +
                   ";Database='Exercise1';Integrated Security=yes;"))
        {
            SqlCommand cmdDepartments =
                new SqlCommand("INSERT INTO Management.Departments VALUES(" +
                               "'" + txtDepartmentCode.Text + "', '" +
                               txtDepartment.Text + "');",
                               cntExercise);

            cntExercise.Open();
            cmdDepartments.ExecuteNonQuery();

            txtDepartmentCode.Text = "";
            txtDepartment.Text = "";
        }

        ShowDepartments();
    }

    private void btnCloseClick(object sender, EventArgs e)
    {
        Close();
    }
}

To start a new file, on the main menu, click File -> New
When asked whether you want to save, click Save
In the top combo box, select the C: drive
On the Toolbar, click New Folder
Type ClientServer and press Enter twice (to display the folder in the top combo box)
Change the name of the file to "Departments.cs"
Click Save

In the empty document, type the following:

using System;
using System.Data;
using System.Drawing;
using System.Windows.Forms;
using System.Data.SqlClient;

public class Employees : Form
{
    private string serverName;

    private DataGridView  dgvEmployees;
    private Label         lblEmployeeNumber;
    private MaskedTextBox txtEmployeeNumber;
    private Label 	  lblFirstName;
    private TextBox 	  txtFirstName;
    private Label 	  lblLastName;
    private TextBox 	  txtLastName;
    private Label 	  lblDepartment;
    private ComboBox 	  cbxDepartments;
    private Label 	  lblTitle;
    private TextBox 	  txtTitle;
    private Button 	  btnAdd;
    private GroupBox 	  gbxNewEmployee;
    private Button 	  btnClose;

    public Employees()
    {
        InitializeComponent();
    }

    private void InitializeComponent()
    {
        dgvEmployees = new DataGridView();
        dgvEmployees.TabIndex = 0;
        dgvEmployees.Size = new System.Drawing.Size(373, 145);
        dgvEmployees.Location = new System.Drawing.Point(12, 12);
        dgvEmployees.Anchor = AnchorStyles.Top  | AnchorStyles.Bottom |
			      AnchorStyles.Left | AnchorStyles.Right;
         dgvEmployees.ColumnHeadersHeightSizeMode = DataGridViewColumnHeadersHeightSizeMode.AutoSize;

        lblEmployeeNumber = new Label();
        lblEmployeeNumber.TabIndex = 0;
        lblEmployeeNumber.AutoSize = true;
        lblEmployeeNumber.Text = "Employee #:";
        lblEmployeeNumber.Size = new System.Drawing.Size(66, 13);
        lblEmployeeNumber.Location = new System.Drawing.Point(15, 22);

        txtEmployeeNumber = new MaskedTextBox();
        txtEmployeeNumber.TabIndex = 1;
        txtEmployeeNumber.Mask = "000-000";
        txtEmployeeNumber.Size = new System.Drawing.Size(53, 20);
        txtEmployeeNumber.Location = new System.Drawing.Point(114, 22);

        lblFirstName = new Label();
        lblFirstName.TabIndex = 2;
        lblFirstName.AutoSize = true;
        lblFirstName.Text = "First Name:";
        lblFirstName.Size = new System.Drawing.Size(60, 13);
        lblFirstName.Location = new System.Drawing.Point(15, 53);

        txtFirstName = new TextBox();
        txtFirstName.TabIndex = 3;
        txtFirstName.Size = new System.Drawing.Size(141, 20);
        txtFirstName.Location = new System.Drawing.Point(114, 50);

        lblLastName = new Label();
        lblLastName.TabIndex = 4;
        lblLastName.AutoSize = true;
        lblLastName.Text = "Last Name:";
        lblLastName.Size = new System.Drawing.Size(61, 13);
        lblLastName.Location = new System.Drawing.Point(15, 79);

        txtLastName = new TextBox();
        txtLastName.TabIndex = 5;
        txtLastName.Size = new System.Drawing.Size(141, 20);
        txtLastName.Location = new System.Drawing.Point(114, 76);

        lblDepartment = new Label();
        lblDepartment.TabIndex = 6;
        lblDepartment.AutoSize = true;
        lblDepartment.Text = "Department:";
        lblDepartment.Size = new System.Drawing.Size(65, 13);
        lblDepartment.Location = new System.Drawing.Point(15, 105);

        cbxDepartments = new ComboBox();
        cbxDepartments.TabIndex = 7;
        cbxDepartments.FormattingEnabled = true;
        cbxDepartments.Size = new System.Drawing.Size(141, 21);
        cbxDepartments.Location = new System.Drawing.Point(114, 101);

        btnAdd = new Button();
        btnAdd.Text = "Add";
        btnAdd.TabIndex = 10;
        btnAdd.UseVisualStyleBackColor = true;
        btnAdd.Size = new System.Drawing.Size(75, 23);
        btnAdd.Location = new System.Drawing.Point(281, 154);
        btnAdd.Click += new System.EventHandler(btnAdd_Click);

        lblTitle = new Label();
        lblTitle.TabIndex = 8;
        lblTitle.Text = "Title:";
        lblTitle.AutoSize = true;
        lblTitle.Size = new System.Drawing.Size(30, 13);
        lblTitle.Location = new System.Drawing.Point(15, 131);

        txtTitle = new TextBox();
        txtTitle.TabIndex = 9;
        txtTitle.Size = new System.Drawing.Size(242, 20);
        txtTitle.Location = new System.Drawing.Point(114, 128);

        gbxNewEmployee = new GroupBox();
        gbxNewEmployee.Text = "New Employee";
        gbxNewEmployee.Size = new System.Drawing.Size(373, 193);
        gbxNewEmployee.Location = new System.Drawing.Point(12, 168);
        gbxNewEmployee.Anchor = AnchorStyles.Bottom | AnchorStyles.Left | AnchorStyles.Right;

        gbxNewEmployee.Controls.Add(lblEmployeeNumber);
        gbxNewEmployee.Controls.Add(txtEmployeeNumber);
        gbxNewEmployee.Controls.Add(lblFirstName);
        gbxNewEmployee.Controls.Add(txtFirstName);
        gbxNewEmployee.Controls.Add(lblLastName);
        gbxNewEmployee.Controls.Add(txtLastName);
        gbxNewEmployee.Controls.Add(lblDepartment);
        gbxNewEmployee.Controls.Add(cbxDepartments);
        gbxNewEmployee.Controls.Add(lblTitle);
        gbxNewEmployee.Controls.Add(txtTitle);
        gbxNewEmployee.Controls.Add(btnAdd);

        btnClose = new Button();
        btnClose.TabIndex = 2;
        btnClose.Text = "Close";
        btnClose.UseVisualStyleBackColor = true;
        btnClose.Size = new System.Drawing.Size(75, 23);
        btnClose.Location = new System.Drawing.Point(293, 376);
        btnClose.Anchor = AnchorStyles.Bottom | AnchorStyles.Right;
        btnClose.Click += new System.EventHandler(btnClose_Click);
 
         Text = "Employees";
        ClientSize = new System.Drawing.Size(401, 412);
    
	Controls.Add(dgvEmployees);
        Controls.Add(gbxNewEmployee);
        Controls.Add(btnClose);
         
        StartPosition = FormStartPosition.CenterScreen;
        Load += new System.EventHandler(Employees_Load);
    }

    private void ShowEmployees()
    {
        using (SqlConnection cntExercise =
                new SqlConnection("Data Source=" + serverName +
                    ";Database='Exercise1';Integrated Security=yes;"))
        {
            SqlCommand cmdEmployees =
                new SqlCommand("SELECT ALL * FROM Personnel.Employees;", cntExercise);

            SqlDataAdapter odaEmployees = new SqlDataAdapter(cmdEmployees);
            DataSet dsEmployees = new DataSet("EmployeesSet");

            cntExercise.Open();

            odaEmployees.Fill(dsEmployees);
            dgvEmployees.DataSource = dsEmployees.Tables[0];
        }
    }

    private void Employees_Load(object sender, EventArgs e)
    {
        // Replace EXPRESSION with the name of the computer
        // on which Microsoft SQL Server is installed
        serverName = "EXPRESSION";
        ShowEmployees();

        using (SqlConnection cntExercise =
                new SqlConnection("Data Source=" + serverName +
                    ";Database='Exercise1';Integrated Security=yes;"))
        {
            SqlCommand cmdDepartments =
                new SqlCommand("SELECT ALL * FROM Management.Departments;", cntExercise);

            cntExercise.Open();
            SqlDataReader rdrDepartment = cmdDepartments.ExecuteReader();

            while(rdrDepartment.Read())
                cbxDepartments.Items.Add(rdrDepartment.GetString(0) + " - " + rdrDepartment.GetString(1));
        }
    }

    private void btnAdd_Click(object sender, EventArgs e)
    {
        if (string.IsNullOrEmpty( txtEmployeeNumber.Text))
        {
            MessageBox.Show("You must enter an employee number.",
                            "Exercise", MessageBoxButtons.OK,
                            MessageBoxIcon.Information);
            return;
        }

        if (string.IsNullOrEmpty(txtLastName.Text))
        {
            MessageBox.Show("You must enter thelast name of the employee.",
                            "Exercise", MessageBoxButtons.OK,
                            MessageBoxIcon.Information);
            return;
        }

        using (SqlConnection cntExercise =
               new SqlConnection("Data Source=" + serverName +
                   ";Database='Exercise1';Integrated Security=yes;"))
        {
            SqlCommand cmdDepartments =
                new SqlCommand("INSERT INTO Personnel.Employees VALUES(" +
                               "'" + txtEmployeeNumber.Text + "', '" +
                               txtFirstName.Text + "', '" +
                               txtLastName.Text + "', '" +
                               cbxDepartments.Text.Substring(0, 5) + "', '" +
                               txtTitle.Text + "');",
                               cntExercise);

            cntExercise.Open();
            cmdDepartments.ExecuteNonQuery();

            txtEmployeeNumber.Text = "";
            txtFirstName.Text = "";
            txtLastName.Text = "";
            cbxDepartments.Text = "";
            txtTitle.Text = "";
        }

        ShowEmployees();
    }

    private void btnClose_Click(object sender, EventArgs e)
    {
        Close();
    }
}

To create a new file, on the main menu, click File -> New
When asked whether you want to save, click Save
Make sure the top combo box displays ClientServer.
Set the name of the file to "Employees.cs"
Click Save

In the empty document, type the following:

using System;
using System.Data;
using System.Drawing;
using System.Windows.Forms;

public class Exercise : Form
{
    private Button btnDepartments;
    private Button btnEmployees;
    private Button btnClose;

    public Exercise()
    {
        InitializeComponent();
    }

    private void InitializeComponent()
    {
        btnDepartments = new Button();
        btnDepartments.TabIndex = 0;
        btnDepartments.Text = "Departments...";
        btnDepartments.UseVisualStyleBackColor = true;
        btnDepartments.Size = new System.Drawing.Size(259, 65);
        btnDepartments.Location = new System.Drawing.Point(21, 12);
        btnDepartments.Font = new System.Drawing.Font("Century Schoolbook",
						      21.75F,
				  		      System.Drawing.FontStyle.Bold,
						      System.Drawing.GraphicsUnit.Point,
						      0);
        btnDepartments.Click += new System.EventHandler(this.btnDepartments_Click);

        btnEmployees = new Button();
        btnEmployees.TabIndex = 1;
        btnEmployees.Text = "Employees...";
        btnEmployees.UseVisualStyleBackColor = true;
        btnEmployees.Size = new System.Drawing.Size(259, 65);
        btnEmployees.Location = new System.Drawing.Point(21, 94);
        btnEmployees.Font = new System.Drawing.Font("Century Schoolbook",
						    21.75F,
						    System.Drawing.FontStyle.Bold,
						    System.Drawing.GraphicsUnit.Point,
						    0);
        btnEmployees.Click += new System.EventHandler(this.btnEmployees_Click);

        btnClose = new Button();
        btnClose.TabIndex = 2;
        btnClose.Text = "Close";
        btnClose.UseVisualStyleBackColor = true;
        btnClose.Size = new System.Drawing.Size(259, 65);
        btnClose.Location = new System.Drawing.Point(21, 176);
        btnClose.Font = new System.Drawing.Font("Century Schoolbook",
						21.75F,
						System.Drawing.FontStyle.Bold,
						System.Drawing.GraphicsUnit.Point,
						0);
        btnClose.Click += new System.EventHandler(this.btnClose_Click);

        ClientSize = new System.Drawing.Size(301, 263);
        Controls.Add(this.btnClose);
        Controls.Add(this.btnEmployees);
        Controls.Add(this.btnDepartments);
        StartPosition = FormStartPosition.CenterScreen;
        Text = "Client/Server Exercise";
    }

    private void btnDepartments_Click(object sender, EventArgs e)
    {
        Departments depts = new Departments();
        depts.Show();
    }

    private void btnEmployees_Click(object sender, EventArgs e)
    {
        Employees empls = new Employees();
        empls.Show();
    }

    private void btnClose_Click(object sender, EventArgs e)
    {
        Close();
    }
}

public class Program
{
    [STAThread]
    static int Main()
    {
        Application.EnableVisualStyles();
        Application.SetCompatibleTextRenderingDefault(false);
        Application.Run(new Exercise());

	return 0;
    }
}

To close Notepad, on the main menu, click File -> Exit
When asked whether you want to save, click Save
Set the file name to "Exercise.cs"
Click Save
To open the Command Prompt (Start -> All Programs -> Accessories -> Command Prompt)
To switch to the root, type CD\ and press Enter
To switch to the folder that contains the files of this project, type CD ClientServer and press Enter

To build and compile the project, type the following:

C:\Windows\Microsoft.NET\Framework\v4.0.30319\csc /r:System.dll
/r:System.Drawing.dll /r:System.Data.dll /r:System.Xml.dll /r:System.Windows.For
ms.dll /target:winexe Departments.cs Employees.cs Exercise.cs

Press Enter
To execute, type Exercise and press Enter

Exercise

You can copy the executable that was created, named Exercise.exe, and paste it in the computers that need to access the database.

Practical Learning: Using the Application

Click Departments

Create a few deparments as follows:

Department Code	Department
HMNRS	Human Resources
ITECM	Information Technology and Management
ACCNT	Accounting

Close the Departments form
Click Employees

Create a few employees as follows:

Employee #	First Name	Last Name	Department	Title
270-284	Paul	Motto	HMNRS	General Manager
579-485	Joan	Stohl	ITECM	Webmaster
852-662	Thomas	Pratt	HMNRS	Intern
279-484	Martine	Schlamme	ACCNT	Accountant

Close the forms