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This chapter is from the book

This chapter is from the book

Your First C# Windows Application

You are about to discover that C# Windows applications are built in an atmosphere very similar to that of Visual Basic.

A C# Windows project is started in a manner similar to a console project except, of course, the Windows option is selected. Start the Visual Studio and select the File | New | Project menu sequence to open the New Project dialog box, as shown in Figure 1–6.

Figure 6Figure 1-6 The New Project dialog box for a C# Windows project.

Figure 7Figure 1-7 The default C# design pane for Windows projects.

Name this project CircleArea and set the subdirectory off of the root directory as shown in Figure 1–6.

Click Finish. The AppWizard creates the template code for the project and takes you to the design pane shown in Figure 1–7.

If you are familiar with Visual Basic, you will recognize this project design area. When you build C# Windows applications, you'll graphically design forms in this designer pane.

To create a working form that will eventually take on the appearance of a dialog box with controls, we need to view optional controls. We can see these controls by opening the toolbox. To do this, use the View | Toolbox menu selection, as shown in Figure 1–8.

Figure 8Figure 1-8 This option brings the toolbox to the design area.

Optionally, you can select the toolbox with the Ctrl+Alt+X key sequence. When the toolbox is selected, you see a variety of controls that can be used in your form design. Figure 1–9 shows the toolbox and an altered form.

To produce the altered form, shown in Figure 1–9, place the mouse over a label control in the toolbox. Hold down the left mouse button and drag the control to the form. Once on the form, the control can be moved and sized to the position shown in Figure 1–9. In a similar manner, move a button control from the toolbox to the form.

Figure 9Figure 1-9 An altered form with the toolbox in the left pane.

Double-click the mouse on the button once it is sized and placed. This adds a Button1_Click method to the project's code that we will alter shortly.

Now, we want to switch from the designer view to the code view to examine the template code written by the AppWizard. To switch to the code view, use the View | Code menu sequence as shown in Figure 1–10.

Figure 10Figure 1-10 Use the Code menu option to view the AppWizard's code.

Another option is to just press F7 when in the designer view to switch to the code view. To switch from the code view back to the designer view requires just a Shift+F7 hot key combination.

When you make the code view selection, you should see a project code listing very similar to the one in the following example. Note that several long lines of programming code are broken and wrapped to the next line. This is necessary because of book page restrictions.

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

namespace CircleArea
{
    /// <summary>
    /// Summary description for Form1.
    /// </summary>
    public class Form1 : System.Windows.Forms.Form
    {
        /// <summary>
        /// Required designer variable.
        /// </summary>
        private System.ComponentModel.Container components
                = null;
        private System.Windows.Forms.Button button1;
        private System.Windows.Forms.Label label1;

        public double radius = 12.3;

        public Form1()
        {
            //
            // Required for Windows Form Designer support
            //
            InitializeComponent();

            //
            // TODO: Add any constructor code after
            // InitializeComponent call
            //
        }

        /// <summary>
        /// Clean up any resources being used.
        /// </summary>
        protected override void Dispose( bool disposing )
        {
            if( disposing )
            {
                if (components != null) 
                {
                    components.Dispose();
                }
            }
            base.Dispose( disposing );
        }

        #region Windows Form Designer generated code
        /// <summary>
        /// Required method for Designer support – do
        /// not modify the contents of this method with

        /// the code editor.
        /// </summary>
        private void InitializeComponent()
        {
            this.components = new System.ComponentModel.
                                  Container();
            this.Size = new System.Drawing.Size(296, 165);
            this.Text = "Form1";
            this.label1 = new System.Windows.Forms.Label();
            this.button1 = new System.Windows.Forms.Button();
            label1.Location = new System.Drawing.
                                  Point(40, 48);
            label1.Text = "label1";
            label1.Size = new System.Drawing.Size(224, 24);
            label1.TabIndex = 0;
            button1.Location = new System.Drawing.
                                   Point(104, 104);
            button1.Size = new System.Drawing.Size(88, 32);
            button1.TabIndex = 2;
            button1.Text = "button1";
            button1.Click += new System.EventHandler
                                 (this.button1_Click);
            this.AutoScaleBaseSize = new System.Drawing.
                                         Size(5, 13);
            this.Controls.Add (this.button1);
            this.Controls.Add (this.label1);
        }
        #endregion

        /// <summary>
        /// The main entry point for the application.
        /// </summary>
        [STAThread]
        static void Main() 
        {
            Application.Run(new Form1());
        }

        private void button1_Click(object sender,
                                   System.EventArgs e)
        {
            label1.Text = (radius * radius * 22 / 7).
                          ToString();
        }
    }
}

All of the code you see, except for the code in boldface, was added by the AppWizard or the designer pane as you added various controls to the project. This is old news for Visual Basic programmers, but a startling surprise for C and C++ programmers!

Add the code shown in boldface in the previous listing. Now use the Build | Rebuild menu selection to build the application. Use the Debug | Run Without Debugger menu option to execute the program code. You should see a window similar to that shown in Figure 1–11.

Figure 11Figure 1-11 The default CircleArea project window.

Figure 12Figure 1-12 The area of a circle is calculated.

Move the mouse to button1 and click it. The application responds to this event and calculates the area of the circle for which the radius was specified in the application. Your screen should now reflect the change and appear similar to Figure 1–12.

The answer shown in the label is the area of a circle with a radius of 12.3. All of this was accomplished by writing only two lines of code. Isn't the remainder of this book going to be fun?

Additional Program Details

The code in the CircleArea project is more complicated than the console application created at the beginning of this chapter. In this section, we'll examine the structure of the template code and leave the details of forms and controls for later chapters. In the following sections we'll examine key portions of the template code in an attempt to understand the structure of all C# Windows projects.

Namespaces

The projects' namespace is named CircleArea. In the following listing, you also see additional namespaces added by the AppWizard for this C# Windows project.

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

namespace CircleArea

The System namespace is a fundamental core namespace used by all C# projects. It provides the required classes, interfaces, structures, delegates, and enumerations required of all C# applications.

The System.Drawing namespace provides access to a number of drawing tools. For example, the namespace classes include Brushes, Cursor, Fonts, Pens, and so on. The namespace structures include Color, Point, and Rectangle. Do you recall the Point structure from earlier in this chapter? The namespace enumerations include BrushStyle and PenStyle.

The System.Collections namespace contains the ArrayList, BitArray, Hashtable, Stack, StringCollection, and StringTable classes. The System.ComponentModel namespace provides support for the following classes; ArrayConverter, ByteConverter, DateTimeConverter, Int16Converter, Int32Converter, Int64Converter, and so on. Delegate support is also provided for a variety of event handler delegates.

The System.Windows.Forms namespace provides class support for a variety of forms and controls. For example, classes are provided for Border, Button, CheckBox, CommonDialog, Forms, and ListBox. This class support spans dialog boxes, forms, and controls. Delegate support is provided for both forms and controls. Enumerations include enumerations for styles and states for forms and controls.

The System.Data namespace provides class support for handling data. Enumerations allow various actions to be performed on data, including various sort options.

For a more detailed look at each of these namespaces, use the Visual Studio NET Help options. Just be sure to set C# as the filter, as shown in Figure 1–13.

Figure 13Figure 13 Additional namespace details are available with the Visual Studio NET Help engine.

You may want to stop at this point and examine other namespaces such as Windows.Forms and so on using the Help engine.

The Form

The next portion of code shows the basic class for the project, named Form1. Every application uses one form, so it should not be a surprise that the naming convention for the class is the name of the base form, in this case Form1.

public class Form1 : System.Windows.Forms.Form
{
    public double radius = 12.3;
     .
     . 
     .
    /*
    * The main entry point for the application.
    *
    */
    public static void Main(string[] args) 
    {
        Application.Run(new Form1());
    }
}

The description for the Form1 class encompasses all of the remaining code in the project. Here you will see variable declarations, control declarations, a variety of component initializations, control methods and, of course, Main().

Designer Variables

In this section, you will find listed the components that are used in the project.

/// <summary>
/// Required designer variable.
/// </summary>
private System.ComponentModel.Container components = null;
private System.Windows.Forms.Button button1;
private System.Windows.Forms.Label label1;

From our discussion of namespaces, note that the project's container is brought into the project via the System.ComponentModel namespace. In a similar manner, the Button and Label controls, named by default button1 and label1, are supported by the System.Windows.Forms namespace.

Initializing Components

The next portion of code initializes components for the project. Components include the form, controls placed on the form, form properties, and so on.

#region Windows Form Designer generated code
/// <summary>
/// Required method for Designer support - do not modify
/// the contents of this method with the code editor.
/// </summary>
private void InitializeComponent()
{
    this.components = new System.ComponentModel.Container();
    this.Size = new System.Drawing.Size(296, 165);
    this.Text = "Form1";
    this.label1 = new System.Windows.Forms.Label();
    this.button1 = new System.Windows.Forms.Button();
    label1.Location = new System.Drawing.Point(40, 48);
    label1.Text = "label1";
    label1.Size = new System.Drawing.Size(224, 24);
    label1.TabIndex = 0;
    button1.Location = new System.Drawing.Point(104, 104);
    button1.Size = new System.Drawing.Size(88, 32);
    button1.TabIndex = 2;
    button1.Text = "button1";
    button1.Click += new System.EventHandler
                         (this.button1_Click);
    this.AutoScaleBaseSize = new System.Drawing.Size(5, 13);
    this.Controls.Add (this.button1);
    this.Controls.Add (this.label1);
}
#endregion

The components and values returned to this portion of code are dependent on the size and placement of the form and any controls placed in the form. All of this work was accomplished using the designer form. Most of these values are initial properties for the form or control they represent. For example:

button1.Location = new System.Drawing.Point(104, 104);
button1.Size = new System.Drawing.Size(88, 32);

This portion of code initializes the Location and Size properties for the Button control, button1. You can view these initial property values as a static or initial form design. Many properties are changed dynamically when the program executes. In this program, for example, the text in the Label control's Text property is changed when the mouse clicks the Button control.

The Event Handler

You might recall that during the design phase of the project, we double-clicked the mouse twice while over the Button control. By doing so, we automatically added a template for a button1_Click event to the application, as follows:

private void button1_Click(object sender, System.EventArgs e)
{
    label1.Text = (radius * radius * 22 / 7).ToString();
}

This simply means that when the button is clicked, the code in this event handler is executed. The code in the event handler has nothing to do with the button event itself. The code in this example says that the Text property of the Label control, label1, will be changed to the string to the right. The string to the right of the equal sign is actually a numeric calculation for the area of a circle with the number converted to a string with the use of ToString().

The End

Finally, the Dispose() method is used to clean up unneeded items:

/// <summary>
/// Clean up any resources being used.
/// </summary>
protected override void Dispose( bool disposing )
{
    if( disposing )
    {
        if (components != null) 
        {
            components.Dispose();
        }
    }
    base.Dispose( disposing );
}

The use of the Dispose() method here frees system resources.

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