Web Part Basics

Web Parts are special controls that are designed to provide the user with discrete units of functionality that can be placed on a page in virtually any location. A discrete unit of functionality essentially means that the Web Parts are designed to perform specific tasks such as displaying an inbox, providing a task list, displaying the current weather, and so on. Web Parts are not entire applications encapsulated in a control. The suite of Web Part tools allows the developer to quickly and easily create pages (called Web Part Pages) that host Web Parts. Such pages can allow users to control the layout by dragging and dropping Web Parts to move them into the location that the user chooses. Users can also control Web Part properties; they can minimize or even close Web Parts just as they would manipulate Windows on their desktop. All of this functionality is virtually free for the developer utilizing the Web Parts suite of controls and ASP.NET 2.0.

There are many reasons to use Web Parts. If you want to provide your users with functionality, but you want your users to be able to choose what data is presented to them, and how that data is presented to them, Web Parts will definitely provide you with a huge boost in productivity, time to market, and application functionality.

Web Parts make use of the personalization provider to store personalization data. When a Web Part is added to a page, it contains both shared data and personalization data. This means that a control can have a set of properties that are shared among all users. When a user chooses to customize that Web Part, his personalization data overrides the shared data, creating user-specific settings. For example, you could create a Weather Web Part that has a shared setting of ZipCode that defaults to the ZIP code of the website's headquarters. When users choose to customize that Web Part with their own ZIP code, they create a user-specific setting that overrides the shared default.

Figure 26.1 shows a conceptual mock-up of what a sample Web Part Page might look like. The page has been divided into zones in which Web Parts can reside. The page in Figure 26.1 has Web Parts for displaying news, weather, a to-do list, the user's inbox, and a site navigation control. A fully functioning Web Part Page containing these Web Parts would allow the user to choose which parts were visible, where those parts sat on the page, and even things like whether the part should display a header or a border. If the Web Part had custom properties (such as the ZIP code for local weather), the user could also choose to supply that information.

Figure 26.1. A Web Part Page conceptual diagram.

Several controls and classes provide the core framework for Web Parts. Table 26.1 contains a list of the key component controls required to make the Web Parts functionality possible.

Table 26.1. Web Part Controls

Control	Description
WebPartManager	The WebPartManager is a UI-less component that resides on a Web Form and manages all Web Parts on that page. Every Web Part Page has one and only one WebPartManager.
WebPartZone	A special type of container control that contains Web Parts within a ZoneTemplate. Pages are typically divided into zones such as a header, footer, center, left, and right.
EditorZone	A container control that contains Web Parts that enable users to edit and personalize Web Parts on a page.
CatalogZone	A container control that contains CatalogPart controls. Use this zone to provide users with a list of Web Parts that they can add to a page that might not be on the page by default.

Additional controls are used in conjunction with the ones listed in Table 26.1, but the ones in Table 26.1 are the controls you should be concerned with at the top level.

The key to working with Web Parts is in knowing what they can and cannot do. Every time you add a server or user control into a ZoneTemplate within a WebPartZone, that control is encapsulated within a GenericWebPart control. Before you start coding your own Web Parts and working with them, you should know how this class works, because it and the WebPart class form part of the foundation of the Web Parts framework. The GenericWebPart class is generated at runtime to allow user controls and other non-Web Part controls to have access to Web Part functionality.

Table 26.2 and 26.3 show some of the common properties and methods of the WebPart class, the class from which all Web Parts (including GenericWebPart) inherit.

Table 26.2. Common WebPart Properties

Property	Method
AllowClose	Indicates whether the user can close the Web Part. When a Web Part is closed, its associated control bar is also hidden from the page in the default display mode.
AllowConnect	Indicates whether the part can be connected to other parts (connected Web Parts are covered later in this chapter).
AllowEdit	Indicates whether the user can edit the properties of the Web Part.
AllowHide	Indicates whether the user can hide the part.
AllowMinimize	Indicates whether the user can minimize the Web Part.
AllowZoneChange	Indicates whether the user can move the part between zones. Some parts require a minimum amount of room to display and shouldn't be allowed to be moved into a smaller zone.
CatalogIconImageUrl	Gets or sets the icon used to represent the Web Part within a catalog of Web Parts.
ChromeState	Gets or sets whether a Web Part is minimized or normal.
ChromeType	Gets or sets the type of border that surrounds the Web Part.
ConnectErrorMessage	Message displayed to users if a failure occurs when attempting to connect the Web Part to another part.
Description	Gets a description of the Web Part that will be displayed in catalogs and tooltips.
DisplayTitle	The title text displayed in the title bar of the Web Part.
ExportMode	Indicates the portion of the Web Part's properties that can be exported.
HasSharedData	Indicates whether the Web Part has shared personalization data.
HasUserData	Indicates whether the Web Part has user-specific personalization data associated with it.
HelpMode	Indicates the type of help UI displayed for the Web Part.
HelpUrl	The page to open when a user requests help for the part.
Hidden	Indicates whether the part is hidden.
IsClosed	Indicates whether the Web Part is closed.
IsShared	Indicates whether the Web Part is shared.
Subtitle	(Read Only) A string added with the Title property that indicates the full title of the Web Part.
Title	The title of the Web Part.
TitleIconImageUrl	The URL indicating the Web Part's icon in the title bar.
Verbs	The collection of custom verbs associated with the part.
Zone	Gets the zone in which the Web Part currently resides.
ZoneIndex	Gets the relative position within the zone of the Web Part within its current zone.

Table 26.3. Part-Specific Control Methods

Method	Description
CreateEditorParts	Creates instances of custom editor parts that can be used to edit the Web Part in edit mode.
SetPersonalizationDirty	Sets a flag that indicates that the data has changed for the Web Part and needs to be updated in the underlying personalization store.