Andy (Steve) De George
be103da07e
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11 KiB
title, description, ms.date, dev_langs, helpviewer_keywords, ms.assetid
| title | description | ms.date | dev_langs | helpviewer_keywords | ms.assetid | |||
|---|---|---|---|---|---|---|---|---|
| Controls | Learn about Windows Presentation Foundation common UI components, referred to as controls, but which might not inherit from the Control class. | 03/30/2017 |
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3f255a8a-35a8-4712-9065-472ff7d75599 |
Controls
WPF SDK continues to use the term "control" to loosely mean any class that represents a visible object in an application, it is important to note that a class does not need to inherit from the xref:System.Windows.Controls.Control class to have a visible presence. Classes that inherit from the xref:System.Windows.Controls.Control class contain a xref:System.Windows.Controls.ControlTemplate, which allows the consumer of a control to radically change the control's appearance without having to create a new subclass. This topic discusses how controls (both those that do inherit from the xref:System.Windows.Controls.Control class and those that do not) are commonly used in WPF.
Creating an Instance of a Control
You can add a control to an application by using either XAML. All controls can be created similarly.
[!code-xamlControlsOverview#1]
The following example creates the same application in code. For brevity, the creation of the xref:System.Windows.Controls.Grid, grid1, has been excluded from the sample. grid1 has the same column and row definitions as shown in the preceding XAML example.
[!code-csharpControlsOverview#2] [!code-vbControlsOverview#2]
Changing the Appearance of a Control
It is common to change the appearance of a control to fit the look and feel of your application. You can change the appearance of a control by doing one of the following, depending on what you want to accomplish:
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Change the value of a property of the control.
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Create a xref:System.Windows.Style for the control.
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Create a new xref:System.Windows.Controls.ControlTemplate for the control.
Changing a Control's Property Value
Many controls have properties that allow you to change how the control appears, such as the xref:System.Windows.Controls.Control.Background%2A of a xref:System.Windows.Controls.Button. You can set the value properties in both XAML and code. The following example sets the xref:System.Windows.Controls.Control.Background%2A, xref:System.Windows.Controls.Control.FontSize%2A, and xref:System.Windows.Controls.Control.FontWeight%2A properties on a xref:System.Windows.Controls.Button in XAML.
[!code-xamlControlsOverview#3]
The following example sets the same properties in code.
[!code-csharpControlsOverview#4] [!code-vbControlsOverview#4]
Creating a Style for a Control
WPF gives you the ability to specify the appearance of controls wholesale, instead of setting properties on each instance in the application, by creating a xref:System.Windows.Style. The following example creates a xref:System.Windows.Style that is applied to each xref:System.Windows.Controls.Button in the application. xref:System.Windows.Style definitions are typically defined in XAML in a xref:System.Windows.ResourceDictionary, such as the xref:System.Windows.FrameworkElement.Resources%2A property of the xref:System.Windows.FrameworkElement.
[!code-xamlControlsOverview#5]
You can also apply a style to only certain controls of a specific type by assigning a key to the style and specifying that key in the Style property of your control. For more information about styles, see Styling and Templating.
Creating a ControlTemplate
A xref:System.Windows.Style allows you to set properties on multiple controls at a time, but sometimes you might want to customize the appearance of a xref:System.Windows.Controls.Control beyond what you can do by creating a xref:System.Windows.Style. Classes that inherit from the xref:System.Windows.Controls.Control class have a xref:System.Windows.Controls.ControlTemplate, which defines the structure and appearance of a xref:System.Windows.Controls.Control. The xref:System.Windows.Controls.Control.Template%2A property of a xref:System.Windows.Controls.Control is public, so you can give a xref:System.Windows.Controls.Control a xref:System.Windows.Controls.ControlTemplate that is different than its default. You can often specify a new xref:System.Windows.Controls.ControlTemplate for a xref:System.Windows.Controls.Control instead of inheriting from a control to customize the appearance of a xref:System.Windows.Controls.Control.
Consider the very common control, xref:System.Windows.Controls.Button. The primary behavior of a xref:System.Windows.Controls.Button is to enable an application to take some action when the user clicks it. By default, the xref:System.Windows.Controls.Button in WPF appears as a raised rectangle. While developing an application, you might want to take advantage of the behavior of a xref:System.Windows.Controls.Button--that is, by handling the button's click event--but you might change the button's appearance beyond what you can do by changing the button's properties. In this case, you can create a new xref:System.Windows.Controls.ControlTemplate.
The following example creates a xref:System.Windows.Controls.ControlTemplate for a xref:System.Windows.Controls.Button. The xref:System.Windows.Controls.ControlTemplate creates a xref:System.Windows.Controls.Button with rounded corners and a gradient background. The xref:System.Windows.Controls.ControlTemplate contains a xref:System.Windows.Controls.Border whose xref:System.Windows.Controls.Border.Background%2A is a xref:System.Windows.Media.LinearGradientBrush with two xref:System.Windows.Media.GradientStop objects. The first xref:System.Windows.Media.GradientStop uses data binding to bind the xref:System.Windows.Media.GradientStop.Color%2A property of the xref:System.Windows.Media.GradientStop to the color of the button's background. When you set the xref:System.Windows.Controls.Control.Background%2A property of the xref:System.Windows.Controls.Button, the color of that value will be used as the first xref:System.Windows.Media.GradientStop. For more information about data binding, see Data Binding Overview. The example also creates a xref:System.Windows.Trigger that changes the appearance of the xref:System.Windows.Controls.Button when xref:System.Windows.Controls.Primitives.ButtonBase.IsPressed%2A is true.
[!code-xamlControlsOverview#6]
[!code-xamlControlsOverview#7]
Note
The xref:System.Windows.Controls.Control.Background%2A property of the xref:System.Windows.Controls.Button must be set to a xref:System.Windows.Media.SolidColorBrush for the example to work properly.
Subscribing to Events
You can subscribe to a control's event by using either XAML or code, but you can only handle an event in code. The following example shows how to subscribe to the Click event of a xref:System.Windows.Controls.Button.
[!code-xamlControlsOverview#10]
[!code-csharpControlsOverview#8] [!code-vbControlsOverview#8]
The following example handles the Click event of a xref:System.Windows.Controls.Button.
[!code-csharpControlsOverview#9] [!code-vbControlsOverview#9]
Rich Content in Controls
Most classes that inherit from the xref:System.Windows.Controls.Control class have the capacity to contain rich content. For example, a xref:System.Windows.Controls.Label can contain any object, such as a string, an xref:System.Windows.Controls.Image, or a xref:System.Windows.Controls.Panel. The following classes provide support for rich content and act as base classes for most of the controls in WPF.
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xref:System.Windows.Controls.ContentControl-- Some examples of classes that inherit from this class are xref:System.Windows.Controls.Label, xref:System.Windows.Controls.Button, and xref:System.Windows.Controls.ToolTip.
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xref:System.Windows.Controls.ItemsControl-- Some examples of classes that inherit from this class are xref:System.Windows.Controls.ListBox, xref:System.Windows.Controls.Menu, and xref:System.Windows.Controls.Primitives.StatusBar.
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xref:System.Windows.Controls.HeaderedContentControl-- Some examples of classes that inherit from this class are xref:System.Windows.Controls.TabItem, xref:System.Windows.Controls.GroupBox, and xref:System.Windows.Controls.Expander.
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xref:System.Windows.Controls.HeaderedItemsControl--Some examples of classes that inherit from this class are xref:System.Windows.Controls.MenuItem, xref:System.Windows.Controls.TreeViewItem, and xref:System.Windows.Controls.ToolBar.
For more information about these base classes, see WPF Content Model.