Users of applications in the Microsoft Office system are already familiar with using task panes such as the Styles and Formatting task pane in Word. Custom task panes behave like other task panes in the Microsoft Office system. Users can dock custom task panes to different sides of the application window, or they can drag custom task panes to any location in the window. You can create an add-in that displays multiple custom task panes at the same time, and users can control each task pane individually.

The user interface of a custom task pane that you create by using Visual Studio Tools for Office is based on Windows Forms controls. You can use the familiar Windows Forms Designer to design the user interface for a custom task pane. You can also use the data binding support in Windows Forms to bind a data source to controls on the task pane.

All custom task panes that are created by using Visual Studio Tools for Office contain a UserControl object. This user control provides the user interface of your custom task pane. You can create the user control at design time or at run time. If you create the user control at design time, you can use the Windows Forms Designer to construct the user interface of your task pane.

After you create a user control that contains the user interface of the custom task pane, you have to instantiate a CustomTaskPane. To do this, pass the user control to the CustomTaskPaneCollection in your add-in by calling one of the Add methods. This collection is exposed as the CustomTaskPanes field of the ThisAddIn class. The following code example is intended to be run from the ThisAddIn class.

myUserControl1 = New MyUserControl
myCustomTaskPane = Me.CustomTaskPanes.Add(myUserControl1, "My Task Pane")
myCustomTaskPane.Visible = True

myUserControl1 = new MyUserControl();
myCustomTaskPane = this.CustomTaskPanes.Add(myUserControl1, "My Task Pane");
myCustomTaskPane.Visible = true;

The Add methods return a new CustomTaskPane object. You can use this object to modify the appearance of the task pane and to respond to user events.

Custom task panes are associated with a document frame window, which presents a view of a document or item to the user. The task pane is visible only when the associated window is visible.

To determine which window displays the custom task pane, use the appropriate Add method overload when you create the task pane:

• To associate the task pane with the active window, use the CustomTaskPaneCollection..::.Add(UserControl, String) method.

• To associate the task pane with a document that is hosted by a specified window, use the CustomTaskPaneCollection..::.Add(UserControl, String, Object) method.

Outlook, Word, and InfoPath require explicit instructions for when to create or display your task pane when more than one window is open. This makes it important to consider where to instantiate the custom task pane in your code to ensure that the task pane appears with the appropriate documents or items in the application. For more information, see Managing Custom Task Panes in Multiple Application Windows.

By default, the task pane is not visible. To make the task pane visible, you must set the Visible property to true.

Users can close a task pane at any time by clicking the Close button (X) in the corner of the task pane. However, there is no default way for users to open the custom task pane again. If a user closes a custom task pane, that user cannot view the custom task pane again unless you provide a way to display it.

If you create a custom task pane in your add-in, you should also create a UI element, such as a button, that users can click to display or hide your custom task pane. If you create a custom task pane in a Microsoft Office application that supports customizing the Ribbon, you can add a control group to the Ribbon with a button that displays or hides your custom task pane. For a walkthrough that demonstrates how to do this, see Walkthrough: Synchronizing a Custom Task Pane with a Ribbon Button.

If you create a custom task pane in a Microsoft Office application that does not support customizing the Ribbon, you can add a CommandBarButton that displays or hides your custom task pane.

You can control the size and location of a custom task pane by using properties of the CustomTaskPane object. You can make many other changes to the appearance of a custom task pane by using properties of the UserControl object that is contained in the custom task pane. For example, you can specify a background image for a custom task pane by using the BackgroundImage property of the user control.

The following table lists the changes you can make to a custom task pane by using CustomTaskPane properties.

You might want your add-in to respond when the user modifies the custom task pane. For example, if the user changes the orientation of the pane from vertical to horizontal, you might want to reposition the controls.

The following table lists the events that you can handle to respond to changes that the user makes to the custom task pane.