he WinForm controls provided by the .NET Framework 1.1 are extremely useful, and the framework for developing new custom controls provided in 1.1 is very strong, but sometimes the development community expects more out-of-the box. Many needs of the development community are satisfied by the basic collection of WinForm controls while some developers have voiced their need for more functionality. Microsoft appears ready to rise to the occasion with the inclusion of many new WinForm controls.
The set of user controls that are an integral part of Microsoft’s development environments provide the baseline for rapid application development (RAD). Every release of the IDE brings new controls to accelerate the development of user-friendly GUIs. Microsoft has seemed content with providing a strong set of base controls, and a framework allowing the development community and third-party Independent Software Vendors (ISVs) to tackle the really heavy lifting in developing complex controls.
Microsoft is starting to break with that strategy with Visual Studio .NET and really follows through with the new controls that appear in the Toolbox of the alpha build of Whidbey. The new controls include everything from data-centric, to layout-oriented containers, to significantly improved versions of existing controls. A few new controls plug up holes in the existing user control line-up.
It is probable that many new or improved WinForm controls covered in this article will change, perhaps dramatically, as Whidbey progresses from alpha through beta to the final release, and new controls could surface. What you can expect for sure is that the quality, ease-of-use, and RAD characteristics of the new WinForm controls will continue to increase beyond the already impressive alpha.
Simplifying Common Tasks
A Better Toolbar
A More Powerful ListView
Figure 4. Update ListView Control: The ListView control is significantly improved, adding features including individual ListViewItem tooltips and owner-draw support.
The ListViewcontrol is already very flexible. It supports multiple views, including LargeIconand SmallIcon, and the ability to automatically add checkboxes to items in the Itemscollection. Several missing features are being added to both the ListViewand TreeViewclasses. You can control how each individual item within the ListView is drawn by setting the OwnerDrawproperty to True and then handle the DrawItemevent of the ListView.
If you want to specify item-specific tooltips, you can set the ShowItemToolTipsproperty to True and set individual ToolTipTextvalues for each instance of a ListViewItem that you add to the Items collection. Both techniques are shown in Figure 4.
There is a new grouping feature using the ListViewGroup class that allows ListViewItems within a ListView class to be grouped according to custom settings and visually associated with each other when the View property of the ListView class is set to any value other than List. ListView groups are available only on Windows XP and Windows Server 2003.
Active Document Editing You’ll use the new ActiveDocumentHost class to display and edit in-place assorted active documents directly from your Windows application. Examples of active documents include rich text-format files and Office documents. You will use the ActiveDocumentHost class to load documents initially in static read-only mode.
Figure 5. The ActiveDocumentHost Class: This class simplifies viewing and editing active documents.
The ActiveDocumentHost class provides some very powerful features. You can set the DrawMode property to Normal, Stretch, or Zoom to control the display mode when the document is inactive. You can set the ActivationGesture property to Click, DoubleClick, Focus, or Never to control which action switches the document to edit mode. You can use the ShowMenus and ShowToolbars properties to modify the look of the document when active and you can set the Tooltarget property to the object that houses the toolbars when the document is active.
As shown in Figure 5, all the toolbars, menu bars, and appropriate editing elements of the original application are hosted in the Windows application, and the document itself becomes editable. The originating application must be installed on the local computer in order to host a document within an instance of the ActiveDocumentHost class
Finally! A Managed WebBrowser The strength of the COM interoperability services in the .NET Framework is excellent. Despite the strength of the APIs and the flexibility of Visual Studio .NET for hiding how complex it can be to use the System.Runtime.InteropServices namespace, you most likely found that using complex COM objects or ActiveX controls can produce less than perfect results in some cases. The WebBrowser object found in Shdocvw.dll is a fair example. This ActiveX component provides the Web page and HTML visual rendering services of Internet Explorer. Through COM interop, it was trivial to use this browser component on a WinForm application, but a few desirable features did not exist, or were complicated to implement.
The new managed WebBrowser class is found in the System.Windows.Forms namespace and extends the functionality provided by the underlying ActiveX control. The rendering behavior did not change, but events have been cleaned up and reorganized, and additional information is available in certain events. Many new properties provide functionality not easily accessible through the underlying browser component.
The WebBrowser class exposes several core navigation events you can handle to process the loading of a document. The primary navigation-related events, in chronological order, are:
The Navigating event can be cancelled if desired conditions do not exist. The Navigating event wraps and replaces the BeforeNavigate2 event of the underlying component, which was not handled correctly when using a generic COM-interop assembly wrapper. You can use the Stop method to cancel any active loading operation and the Refresh method to force the WebBrowser class to load the desired document.
Navigation is initiated by the WebBrowser object whenever one of the following methods is executed:
A more complete list of methods provided by the WebBrowser class is provided in Table 1
Table 1: The WebBrowser methods provide core navigation and dialog box display features expected in a browsing control.
Navigates to the previous document in the navigation list if one exists. The return value indicates whether a previous entry is available.
Navigates to the subsequent document in the navigation list if one exists. The return value indicates whether a subsequent entry is available.
Navigates to the Home page configured by Internet Explorer.
Navigates to the Search page configured by Internet Explorer.
Basic navigation method used to initiate navigation to a document found at the specified URL
Sends the currently loaded document to the printer as specified by the current default printer settings
Reloads the document currently displayed in the WebBrowser control by checking the server for an updated version
Opens the Internet Explorer Page Setup dialog box
Opens the Internet Explorer Print dialog box
Opens the Internet Explorer Print Preview dialog box
Opens the Internet Explorer Page Properties dialog box
Opens the Internet Explorer Save As dialog box
Cancels any pending navigation and stops any dynamic page elements, such as background sounds and animations.
Navigation is also initiated when one of the following properties is changed:
Figure 6. Using the Managed WebBrowser: The new managed WebBrowser class wraps and significantly extends the features previously requiring a generic COM-interop assembly, wrapping the WebBrowser ActiveX control found in shdocvw.dll.
The DocumentCompleted event is your primary mechanism for processing a loaded Web page. When handling this event, you access the Web page contents through the Document, DocumentText, or DocumentStream properties. Manually setting the DocumentText or DocumentStream properties causes the WebBrowser class to first navigate to about:blank. This provides a fully instantiated document object to hold the page contents.
By using the same icons found on the Internet Explorer toolbars, I approximated the look of Internet Explorer. This is a simple example of leveraging the WebBrowser control to create a custom browser application. An example of combining a couple of WinBar controls and a WebBrowser control onto a form is shown in Figure 6.
The FileDownload event should be handled to execute code before the Internet Explorer File Download dialog box is displayed. You should handle this event if you want to cancel a file download operation. If you want to cancel the loading of a new browser window, handle the NewWindow event that is raised before a new browser window is opened. Additional events provided by the WebBrowser class are listed in Table 2.
Table 2:WebBrowser events provide critical feedback on the navigation process to allow the implementation of all the standard visual indicators to the application user.
Changing the CanGoBack property raises this event.
Changing the CanGoForward property raises this event.
Raised when the WebBrowser control finishes loading a document. This is the primary event used to process Web pages after loading.
Changing the DocumentTitle property raises this event.
Navigating to or away from a Web site that uses encryption raises this event.
Raised before the WebBrowser control begins downloading
Raised after the WebBrowser control has navigated to a new document but before it has begun loading
Raised before the WebBrowser control navigates to a new document
Raised before a new browser window is opened
Raised when the WebBrowser control has updated information on the download progress of a document it is navigating to. Typically used to modify a progress bar.
The WebBrowser class provides several properties used to leverage extended functionality that is enhanced beyond the behavior directly exposed by the underlying browser component through generic COM-interop wrappers. The AllowWebBrowserDrop property is set to True to allow the WebBrowser object to automatically navigate to and load a document dragged and dropped onto the control. Set this property to False to disable it. Set the ScriptErrorsSuppressed property to True to disable the display of the scripting error dialog box in response to errors raised within script embedded in a Web page being loaded.
If you want to disable user interaction with the WebBrowser control and the loaded document, use the IsWebBrowserContextMenuEnabled and WebBrowserShortcutsEnabled properties. Set these properties to False to disable the most common methods of user/Web page interaction. Additional properties of the WebBrowser class are listed in Table 3.
Table 3: The WebBrowser class exposes many useful properties, including many extended properties beyond the core set provided by the underlying Internet Explorer component.
Controls whether the WebBrowser control automatically loads and renders a document dropped onto it. Set to False to assist in concealing the use of the WebBrowser control. Default value is True.
Indicates whether a previous entry in the navigation list exists. If True, the WebBrowser control can successfully navigate to a previous location.
Indicates whether a subsequent entry exists in the navigation list. If True, the WebBrowser control can navigate to the next location in the list.
An HtmlDocument object representing the document currently loaded. The HtmlDocument provides an HTML document object model view of the page and allows programmatic manipulation of the HTML items contained in the Web page.
A Stream object used to get or set the contents of the page currently loaded in the WebBrowser control
Represents the HTML contents of the page displayed in the WebBrowser control. A value of “” is returned or used when no document is loaded.
Read-only value representing the title of the Web page, as defined by the HTML
element. Often used to set the text value in the title bar of a form.
The Multipurpose Internet Mail Extensions (MIME) type of the document loaded in the WebBrowser control.
Indicates whether a new document is currently loading
Indicates whether the WebBrowser control is in offline mode. In offline mode, pages are loaded from the local cache.
Determines whether the standard context menu normally displayed when right-clicking on a Web page is shown by the WebBrowser control. Set to False to control user interactions with the loaded document.
Determines the object accessible by scripting code contained within a Web page loaded in the WebBrowser control.
Indicates the current state of the WebBrowser control. Used to provide more information than the IsBusy property.
Indicates whether the WebBrowser control should display scripting error dialog boxes or suppressed them.
Location of the currently loaded document
Retrieves the version of Internet Explorer installed
Retrieves or sets whether keyboard shortcuts are enabled within the WebBrowser control
If you want to enable two-way communication between managed code and client-side script contained within a Web page, use the ObjectForScripting property. Set this property to the object you want referenced by any Web page scripting code when a reference to window.external is made in the script. The window.external object is a built-in DOM object that provides access to the host application of the Web page. Specifically, this provides the page script with a late-bound reference to a managed object and enables communication from the Web page to a managed object.
To make the communication channel two-way, you use the Document property of the WebBrowser instance. This property is an HtmlDocument object instance and provides a managed wrapper around the COM-based MSHTML library. This library is also known as the Microsoft HTML Object Library and it provides you with access to elements within the Web page through the document object model, completing the two-way programmatic communication channel. Use the System.Windows.Forms.InvokeScript method to directly script methods provided by the Web page.
New Container Controls
Figure 7. The SplitContainer Class: This class simplifies the common task of combining Panel controls with a Splitter to achieve a segmented container.
Whidbey includes several new controls that provide advanced layout services. Three new container controls are provided to you to simplify three different control layout scenarios: SplitContainer, FlowLayoutPanel, and TableLayoutPanel.
Simplifying Form Design The SplitContainer control, shown in Figure 7, combines several controls and docking settings commonly used in a single composite control, saving many steps in the development of complex forms. A common task in designing forms is to use controls that could share a vertical or horizontal space. The existing Splitter control allows an application user to adjust the division of space separating sections of a container control, such as a Panel class. Use the SplitContainer control to eliminate the need to perform these combined steps multiple times.
The SplitContainer class provides several properties to modify the behavior of an instance of the control. Use the FixedPanel property to select which panel in the control should not resize as the SplitContainer instance resizes. Set the SplitterDistance and Orientation properties to control the direction and starting location of the splitter bar. The Panel1MinSize and Panel2MinSize properties are used to specify the minimum size of the SplitterPanel instances in the SplitContainer, effectively controlling how close the splitter bar can be placed to either edge of the control.
Reducing Control Layout Code
Figure 8. The FlowLayoutPanel and TableLayoutPanel: These classes provide a combination of container control and positional layout services while differing on the positional logic implemented.
Two closely related controls, the FlowLayoutPanel and TableLayoutPanel classes, extend the Panel class by adding specific child control positioning logic. Use either of these controls to implement a very specific set of child control layout scenarios. In simple scenarios, as shown in Figure 8, the result of using either control may not be uniquely distinguishable from the other.
The FlowLayoutPanel class, mentioned in the Whidbey documentation as the FlowPanel class, is used as a container control when the child controls added are dynamically repositioned to flow in a particular direction. The FlowLayoutPanel automatically positions all child controls in the direction indicated by the value of the FlowDirection property. You can leave the WrapContents property set to the default value of True to force the controls to stay within the boundaries of the SplitContainer class by starting a new row or column, depending on the value of the FlowDirection property. In Figure 9, a FlowLayoutPanel control with a FlowDirection value of Horizontal moves the controls when one of the child controls is increased in size.
The TableLayoutPanel class, mentioned in the Whidbey documentation as the GridPanelclass, implements different positioning logic than the FlowLayoutPanel class. The FlowDirection and WrapContents property of the FlowLayoutPanel are replaced with integer-based Columns and Rows properties. The TableLayoutPanel class implicitly positions child controls in a table format, which, assuming default values of 0 for both Columns and Rows, mimics a FlowLayoutPanel instance with FlowDirection set to Horizontal and WrapContents set to True.
Figure 9. The TableLayoutPanel Class: This class maintains a structured approach to repositioning child controls and the FlowLayoutPanel class offers a more lenient set of positioning rules.
You set either Columns or Rows to a non-zero positive value to limit the cells in either dimension of the table. Increasing the size of a child control shifts the cell size in the table containing the child control to accommodate the larger child control, as shown in Figure 9. This pushes other child controls away from the growing control.
An exception is raised if you set values for Columns and Rows that combine to produce too few cells in the table to hold all the child controls. The TableLayoutPanel class provides ColumnStyles and RowStyles properties. Use these collection-based properties to modify sizing properties at the individual row and column level.
Miscellaneous New Features Of all the enhancements introduced to WinForm controls in Whidbey, the most useful are sometimes the least obvious. Many enhancements are not as obvious as the SplitContainer or the addition of owner-drawn functionality to the ListView and TreeView classes.
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