Controls are added to a Form by creating the control instance and calling the Add method on the Form.Controls property. This property returns an instance of System.Windows.Forms.Control.ControlsCollection.

When a Form is no longer required, the Dispose method must be called; it’s important to ensure that the Dispose method is also called on any controls that the Form contains.

The System.ComponentModel.Container class can be used to track a group of controls, and calling the Dispose method on the Container class ensures that Dispose is also called on all of the controls that have been added to the container.

The following example demonstrates how to add a Button to a Form and how to ensure that controls are correctly disposed of; for more information on disposing of objects, see the Destructors section in Chapter 5. For an overview of controls included in the .NET Framework, see the Control Overview section later in this chapter.

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

public class SimpleForm : Form {

    private System.ComponentModel.Container o_components = null;

    public SimpleForm() {
        o_components = new System.ComponentModel.Container();
        Button x_button = new Button();
        x_button.Text = "My Button";
        Controls.Add(x_button);
        o_components.Add(x_button);
    }

    protected override void Dispose(bool p_disposing) {
        if(p_disposing) {
            if (o_components != null) {
                o_components.Dispose();
            }
        }
        base.Dispose(p_disposing);
    }
}

Windows Forms applications are started by calling the static Run method of the System.Windows.Forms.Application class, normally from the application Main method. The following fragment demonstrates how to run an instance of the SimpleForm class created earlier:

static void Main() {
    Application.Run(new SimpleForm());
}

A Forms application can be terminated either by calling the Application.Exit method or when the user clicks on the Close icon at the top of a form window.

Compiling a Forms application using the command-line compiler is similar to compiling any other C# application. However, you should use the /target:winexe flag to specify that the output is a UI application. Applications built with the /target:exe flag will still work but will cause a command prompt to be displayed to the user alongside the main window. The following statement demonstrates how to compile the SimpleForm.cs file:

csc /target:winexe /out:MyApp.exe SimpleForm.cs

For more information about compiling C# classes, see Chapter 3.

When a control is anchored to the edge of a container, the distance between the edge of the control and the edge of the container remains constant when the container is resized. A control can be anchored to any combination of edges, which causes the control to be resized as needed to maintain the distance between edges.

The following code demonstrates anchoring a button to the left and right edges of the form; the button will be resized as the form is resized to ensure that the distance from the edge of the button to the edge of the form remains constant:

using System.Drawing;
using System.Windows.Forms;
public class LayoutDemo : Form {

    public LayoutDemo() {
        Button x_button = new Button();
        x_button.Text = "My Button";
        x_button.Location = new Point(20, 20);
        x_button.Anchor = AnchorStyles.Left | AnchorStyles.Right;

        Controls.Add(x_button);
    }

    // Other methods, such as Dispose, would go here.

    static void Main() {
        Application.Run(new LayoutDemo());
    }
}

The Anchor property is used to specify a value from the AnchorStyles enumeration; values can be combined using a bit mask, as shown in the statement marked in boldface. Table 18-2 shows the values in the AnchorStyle enumeration.

When a control is docked to an edge of its container, it remains in contact with that edge when the container is resized; the control will be resized to ensure that it is the same size as the docked edge. Docking is specified using the Dock property, as shown in the following example, which docks a button to the left edge of a form; the button will be resized to be completely in contact with the left edge of the form at all times, so it will be resized horizontally to follow the size of the form:

using System.Drawing;
using System.Windows.Forms;
public class LayoutDemo : Form {

    public LayoutDemo() {
        Button x_button = new Button();
        x_button.Text = "My Button";
        x_button.Location = new Point(20, 20);
        x_button.Dock = DockStyle.Left;

        Controls.Add(x_button);
    }

    // Other methods, such as Dispose, would go here.

    static void Main() {
        Application.Run(new LayoutDemo());
    }
}

The Dock property accepts a value from the DockStyle enumeration; Table 18-3 describes the values in this enumeration.