Feature

One of the new features in Visual Studio 2005 (VS2005) is easier custom control development for .NET Compact Framework. This article is about how to use Visual Studio 2005 to create custom control for .NET Compact Framework and provide design-time support.


Introduction to Custom Control
A Windows Forms custom control is a class that derives directly or indirectly from System.Windows.Forms.Control or System.Windows.Forms.
UserControl. Using custom control technology, developers can easily create powerful, reusable and redistributable Windows Forms controls.
   
There are three common custom control scenarios:

• Combine existing controls to author a composite control. In this case, the custom control should derive from System.Windows.Forms.UserControl.
• Extend an existing control to add to its functionality. In this case, the custom control should derive from the existing control, such as System.Windows.Forms.TextBox.
• Author a control that doesn’t depend on existing WinForm controls. In this case, the custom control should derive from System.Windows.Forms.Control.

Visual Studio 2005 fully supports creating custom controls in .NET Compact Framework. In addition, custom control developers can create a great design-time experience for custom control users. Design-time support makes it easier for developers to use custom controls in Visual Studio 2005 Smart Device projects.
   
Usually, building a custom control for .NET Compact Framework consists of two steps:

1. Code the custom control
2. Add design-time support

In this article I am going to illustrate these steps by building a .NET Compact Framework custom control in Visual Studio 2005. The custom control is for sign-in forms and will look like Figure 1 on a Smartphone device. It is called SignInControl. Developers can utilize this custom control to implement a consistent sign-in experience for their apps. It has the following features:

• Can take user name and password input
• Provides animation functionality
• Can be easily used in Visual Studio 2005 designer
• Supports numeric input mode to help Smartphone users

To follow the article, you will need Visual Studio 2005 Beta 2 and Windows Mobile 5 Smartphone SDK.

Code the Custom Control
SignInControl uses Label and TextBox controls to take user input, and PictureBox to display the animation. Thus it should derive from UserControl.
    
The first step is to create a Visual Studio Smart Device project. Visual Studio 2005 has many Smart Device project types to choose from. In this example I am going to create a C# SmartPhone Windows Mobile 5 (code named Magneto) Control Library project called SignInControl (see Figure 2).

 
After creating the project, rename the UserControl1.cs to SignInControl.cs. To protect my custom control assembly from tampering, I also signed my assembly with a strong name key file (right click on the project in the solution explorer, select “Properties,” and click on “Signing” tab). Now I am ready to implement my custom control.
   
Go to the designer and drop two Label controls, two TextBox controls, one PictureBox control, and one Timer component. When doing this, notice the designer automatically displays snap-line to help aligning the controls. Set the Label controls to have proper text, and set the PasswordChar property of the password TextBox to “*.” Figure 3 is a screenshot of SignInControl in the designer.
   
Two properties should be added to SignInControl to give developers access to the user name and password entered. Their implementation simply gets or sets the Text property value on the corresponding TextBox controls.
   
Animation support is provided by the use of Timer and PictureBox. Add a Timer object to SignInControl, set its Interval property to 1000 (one second), and double click it to generate Timer.Tick event handler. The Timer object will raise an event every second. The PictureBox control’s image will be refreshed on each tick to achieve an animation effect.
   
The images for animation are set in AnimationImages property using ImageList. An AnimationMode property is provided so that developers can turn animation on or off. After adding the above implementation, SignInControl.cs looks like Listing 1.

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