| By Xin Yan |
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| July 29, 2005 01:45 AM EDT |
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116,037 |
Besides using code editor, there is another (and easier) way to add properties. It is to use class designer. Right click SignInControl.cs node in the solution explorer, select “View Class Diagram,” and you will see class designer. Class designer gives a graphics representation of the code, and it allows adding, updating, and removing types, properties, methods, and events. Figure 4 is a screen shot of SignInControl in class designer.
To test this custom control, compile the project and add a SmartPhone Windows Mobile 5 WinForm application to the solution. When the form is opened, the SignInControl will be available in the toolbox and can be dropped to the form. If animation is needed, set AnimationMode property to On, add an ImageList to the form, and assign the ImageList to SignInControl’s AnimationImage property. Figure 5 is a screenshot of using SignInControl in designer.
Provide Design-Time SupportBy now a functional custom control is created. It works on a Smartphone device, it appears in Visual Studio 2005 Toolbox and it can be dragged and dropped to the form designer. It looks pretty good but still misses some useful design-time features:
- Properties I added appear in the “Misc” category in the property browser (see Figure 5). Also they do not have descriptions associated with it.
- If user does not change properties such as UserName and Password in the designer, the following code will be generated inside InitializeComponent for the user:
this.signInControl1.Password = "";
this.signInControl1.UserName = "";
This is unnecessary because values of both properties are defaulted to the empty string. Ideally, the above code should not be generated.
These two are both design-time requirements. Most of the design-time support is specified in the form of design-time attributes. A design-time attribute describes how a control will behave at design-time. Some common design-time attributes are:
- BrowsableAttribute
- CategoryAttribute
- DescriptionAttribute
- EditorAttribute
- DesignerSerializationVisibility-Attribute
- And more …
You can find the definition of these attributes from MSDN. In the case of SignInControl, CategoryAttribute, and Descrip-tionAttribute need to be specified for each property to put it in the right category, and give it description.
I found the easiest approach to add design-time attributes is to use class designer. Open class designer as in Figure 4 and select desired property (for example UserName). Notice there is a “Custom Attribute” property in the property browser. Click on its editor button (the “…” button) and custom attribute editor will pop up. Type in the design-time attributes (see Figure 6).
Click OK and repeat the same process for other properties. By now Category and Description design-time attributes are added. Take a look at the solution explorer. A new file named DesignTimeAttributes.xmta is added to the project with the following content supported (see Listing 2).
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