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title ms.custom ms.date ms.prod ms.reviewer ms.suite ms.technology ms.tgt_pltfrm ms.topic helpviewer_keywords ms.assetid caps.latest.revision author ms.author manager
Customizing the Appearance of an Existing Control by Creating a ControlTemplate
03/30/2017
.net-framework
dotnet-wpf
article
control contract [WPF]
controls [WPF], visual structure changes
ControlTemplate [WPF], customizing for existing controls
skinning controls [WPF]
controls [WPF], appearance specified by state
templates [WPF], custom for existing controls
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Customizing the Appearance of an Existing Control by Creating a ControlTemplate

A xref:System.Windows.Controls.ControlTemplate specifies the visual structure and visual behavior of a control. You can customize the appearance of a control by giving it a new xref:System.Windows.Controls.ControlTemplate. When you create a xref:System.Windows.Controls.ControlTemplate, you replace the appearance of an existing control without changing its functionality. For example, you can make the buttons in your application round instead of the default square shape, but the button will still raise the xref:System.Windows.Controls.Primitives.ButtonBase.Click event.

This topic explains the various parts of a xref:System.Windows.Controls.ControlTemplate, demonstrates creating a simple xref:System.Windows.Controls.ControlTemplate for a xref:System.Windows.Controls.Button, and explains how to understand the control contract of a control so that you can customize its appearance. Because you create a xref:System.Windows.Controls.ControlTemplate in [!INCLUDETLA2#tla_xaml], you can change a control's appearance without writing any code. You can also use a designer, such as Microsoft Expression Blend, to create custom control templates. This topic shows examples in the [!INCLUDETLA2#tla_xaml] that customize the appearance of a xref:System.Windows.Controls.Button and lists the complete example at the end of the topic. For more information about using Expression Blend, see Styling a control that supports templates.

The following illustrations show a xref:System.Windows.Controls.Button that uses the xref:System.Windows.Controls.ControlTemplate that is created in this topic.

A button with a custom control template.
A button that uses a custom control template

A button with a red border.
A button that uses a custom control template and has the mouse pointer over it

Prerequisites

This topic assumes that you understand how to create and use controls and styles as discussed in Controls. The concepts discussed in this topic apply to elements that inherit from the xref:System.Windows.Controls.Control class, except for the xref:System.Windows.Controls.UserControl. You cannot apply a xref:System.Windows.Controls.ControlTemplate to a xref:System.Windows.Controls.UserControl.

When You Should Create a ControlTemplate

Controls have many properties, such as xref:System.Windows.Controls.Border.Background%2A, xref:System.Windows.Controls.Control.Foreground%2A, and xref:System.Windows.Controls.Control.FontFamily%2A, that you can set to specify different aspects of the control's appearance, but the changes that you can make by setting these properties are limited. For example, you can set the xref:System.Windows.Controls.Control.Foreground%2A property to blue and xref:System.Windows.Controls.Control.FontStyle%2A to italic on a xref:System.Windows.Controls.CheckBox.

Without the ability to create a new xref:System.Windows.Controls.ControlTemplate for controls, all controls in every [!INCLUDETLA2#tla_winclient]-based application would have the same general appearance, which would limit the ability to create an application with a custom look and feel. By default, every xref:System.Windows.Controls.CheckBox has similar characteristics. For example, the content of the xref:System.Windows.Controls.CheckBox is always to the right of the selection indicator, and the check mark is always used to indicate that the xref:System.Windows.Controls.CheckBox is selected.

You create a xref:System.Windows.Controls.ControlTemplate when you want to customize the control's appearance beyond what setting the other properties on the control will do. In the example of the xref:System.Windows.Controls.CheckBox, suppose that you want the content of the check box to be above the selection indicator and you want an X to indicate that the xref:System.Windows.Controls.CheckBox is selected. You specify these changes in the xref:System.Windows.Controls.ControlTemplate of the xref:System.Windows.Controls.CheckBox.

The following illustration shows a xref:System.Windows.Controls.CheckBox that uses a default xref:System.Windows.Controls.ControlTemplate.

A checkbox with the default control template.
A CheckBox that uses the default control template

The following illustration shows a xref:System.Windows.Controls.CheckBox that uses a custom xref:System.Windows.Controls.ControlTemplate to place the content of the xref:System.Windows.Controls.CheckBox above the selection indicator and displays an X when the xref:System.Windows.Controls.CheckBox is selected.

A checkbox with a custom control template.
A CheckBox that uses a custom control template

The xref:System.Windows.Controls.ControlTemplate for the xref:System.Windows.Controls.CheckBox in this sample is relatively complex, so this topic uses a simpler example of creating a xref:System.Windows.Controls.ControlTemplate for a xref:System.Windows.Controls.Button.

Changing the Visual Structure of a Control

In [!INCLUDETLA2#tla_winclient], a control is often a composite xref:System.Windows.FrameworkElement objects. When you create a xref:System.Windows.Controls.ControlTemplate, you combine xref:System.Windows.FrameworkElement objects to build a single control. A xref:System.Windows.Controls.ControlTemplate must have only one xref:System.Windows.FrameworkElement as its root element. The root element usually contains other xref:System.Windows.FrameworkElement objects. The combination of objects makes up the control's visual structure.

The following example creates a custom xref:System.Windows.Controls.ControlTemplate for the xref:System.Windows.Controls.Button. The xref:System.Windows.Controls.ControlTemplate creates the visual structure of the xref:System.Windows.Controls.Button. This example does not change the button's appearance when you move the mouse pointer over it or click it. Changing the button's appearance when it is in a different state is discussed later in this topic.

In this example, the visual structure consists of the following parts:

  • A xref:System.Windows.Controls.Border named RootElement that serves as the template's root xref:System.Windows.FrameworkElement.

  • A xref:System.Windows.Controls.Grid that is a child of RootElement.

  • A xref:System.Windows.Controls.ContentPresenter that displays the button's content. The xref:System.Windows.Controls.ContentPresenter enables any type of object to be displayed.

[!code-xamlVSMButtonTemplate#BasicTemplate]

Preserving the Functionality of a Control's Properties by Using TemplateBinding

When you create a new xref:System.Windows.Controls.ControlTemplate, you still might want to use the public properties to change the control's appearance. The TemplateBinding markup extension binds a property of an element that is in the xref:System.Windows.Controls.ControlTemplate to a public property that is defined by the control. When you use TemplateBinding, you enable properties on the control to act as parameters to the template. That is, when a property on a control is set, that value is passed on to the element that has the TemplateBinding on it.

The following example repeats the part of the preceding example that uses the TemplateBinding markup extension to bind properties of elements that are in the xref:System.Windows.Controls.ControlTemplate to public properties that are defined by the button.

[!code-xamlVSMButtonTemplate#TemplateBinding]

In this example, the xref:System.Windows.Controls.Grid has its xref:System.Windows.Controls.Panel.Background%2A?displayProperty=nameWithType property template bound to xref:System.Windows.Controls.Control.Background%2A?displayProperty=nameWithType. Because xref:System.Windows.Controls.Panel.Background%2A?displayProperty=nameWithType is template bound, you can create multiple buttons that use the same xref:System.Windows.Controls.ControlTemplate and set the xref:System.Windows.Controls.Control.Background%2A?displayProperty=nameWithType to different values on each button. If xref:System.Windows.Controls.Control.Background%2A?displayProperty=nameWithType was not template bound to a property of an element in the xref:System.Windows.Controls.ControlTemplate, setting the xref:System.Windows.Controls.Control.Background%2A?displayProperty=nameWithType of a button would have no impact on the button's appearance.

Note that the names of the two properties do not need to be identical. In the preceding example, the xref:System.Windows.Controls.Control.HorizontalContentAlignment%2A?displayProperty=nameWithType property of the xref:System.Windows.Controls.Button is template bound to the xref:System.Windows.FrameworkElement.HorizontalAlignment%2A?displayProperty=nameWithType property of the xref:System.Windows.Controls.ContentPresenter. This enables the content of the button to be positioned horizontally. xref:System.Windows.Controls.ContentPresenter does not have a property named HorizontalContentAlignment, but xref:System.Windows.Controls.Control.HorizontalContentAlignment%2A?displayProperty=nameWithType can be bound to xref:System.Windows.FrameworkElement.HorizontalAlignment%2A?displayProperty=nameWithType. When you template bind a property, be sure that the target and source properties are the same type.

The xref:System.Windows.Controls.Control class defines several properties that must be used by the control template to have an effect on the control when they are set. How the xref:System.Windows.Controls.ControlTemplate uses the property depends on the property. The xref:System.Windows.Controls.ControlTemplate must use the property in one of the following ways:

  • An element in the xref:System.Windows.Controls.ControlTemplate template binds to the property.

  • An element in the xref:System.Windows.Controls.ControlTemplate inherits the property from a parent xref:System.Windows.FrameworkElement.

The following table lists the visual properties inherited by a control from the xref:System.Windows.Controls.Control class. It also indicates whether the default control template of a control uses the inherited property value or if it must be template bound.

Property Usage method
xref:System.Windows.Controls.Control.Background%2A Template binding
xref:System.Windows.Controls.Control.BorderThickness%2A Template binding
xref:System.Windows.Controls.Control.BorderBrush%2A Template binding
xref:System.Windows.Controls.Control.FontFamily%2A Property inheritance or template binding
xref:System.Windows.Controls.Control.FontSize%2A Property inheritance or template binding
xref:System.Windows.Controls.Control.FontStretch%2A Property inheritance or template binding
xref:System.Windows.Controls.Control.FontWeight%2A Property inheritance or template binding
xref:System.Windows.Controls.Control.Foreground%2A Property inheritance or template binding
xref:System.Windows.Controls.Control.HorizontalContentAlignment%2A Template binding
xref:System.Windows.Controls.Control.Padding%2A Template binding
xref:System.Windows.Controls.Control.VerticalContentAlignment%2A Template binding

The table lists only the visual properties inherited from the xref:System.Windows.Controls.Control class. Apart from the properties listed in the table, a control may also inherit the xref:System.Windows.FrameworkElement.DataContext%2A, xref:System.Windows.FrameworkElement.Language%2A, and xref:System.Windows.Controls.TextBlock.TextDecorations%2A properties from the parent framework element.

Also, if the xref:System.Windows.Controls.ContentPresenter is in the xref:System.Windows.Controls.ControlTemplate of a xref:System.Windows.Controls.ContentControl, the xref:System.Windows.Controls.ContentPresenter will automatically bind to the xref:System.Windows.Controls.ContentControl.ContentTemplate%2A and xref:System.Windows.Controls.ContentControl.Content%2A properties. Likewise, an xref:System.Windows.Controls.ItemsPresenter that is in the xref:System.Windows.Controls.ControlTemplate of an xref:System.Windows.Controls.ItemsControl will automatically bind to the xref:System.Windows.Controls.ItemsControl.Items%2A and xref:System.Windows.Controls.ItemsPresenter properties.

The following example creates two buttons that use the xref:System.Windows.Controls.ControlTemplate defined in the preceding example. The example sets the xref:System.Windows.Controls.Control.Background%2A, xref:System.Windows.Controls.Control.Foreground%2A, and xref:System.Windows.Controls.Control.FontSize%2A properties on each button. Setting the xref:System.Windows.Controls.Control.Background%2A property has an effect because it is template bound in the xref:System.Windows.Controls.ControlTemplate. Even though the xref:System.Windows.Controls.Control.Foreground%2A and xref:System.Windows.Controls.Control.FontSize%2A properties are not template bound, setting them has an effect because their values are inherited.

[!code-xamlVSMButtonTemplate#ButtonDeclaration]

The preceding example produces output that is similar to the following illustration.

Two buttons, one blue and one purple.
Two buttons with different background colors

Changing the Appearance of a Control Depending on Its State

The difference between a button with its default appearance and the button in the preceding example is that the default button subtly changes when it is in different states. For example, the default button's appearance changes when the button is pressed, or when the mouse pointer is over the button. Although the xref:System.Windows.Controls.ControlTemplate does not change the functionality of a control, it does change the control's visual behavior. A visual behavior describes the control appearance when it is in a certain state. To understand the difference between the functionality and visual behavior of a control, consider the button example. The button's functionality is to raise the xref:System.Windows.Controls.Primitives.ButtonBase.Click event when it is clicked, but the button's visual behavior is to change its appearance when it is pointed to or pressed.

You use xref:System.Windows.VisualState objects to specify the appearance of a control when it is in a certain state. A xref:System.Windows.VisualState contains a xref:System.Windows.Media.Animation.Storyboard that changes the appearance of the elements that are in the xref:System.Windows.Controls.ControlTemplate. You do not have to write any code to make this occur because the control's logic changes state by using the xref:System.Windows.VisualStateManager. When the control enters the state that is specified by the xref:System.Windows.VisualState.Name%2A?displayProperty=nameWithType property, the xref:System.Windows.Media.Animation.Storyboard begins. When the control exits the state, the xref:System.Windows.Media.Animation.Storyboard stops.

The following example shows the xref:System.Windows.VisualState that changes the appearance of a xref:System.Windows.Controls.Button when the mouse pointer is over it. The xref:System.Windows.Media.Animation.Storyboard changes the button's border color by changing the color of the BorderBrush. If you refer to the xref:System.Windows.Controls.ControlTemplate example at the beginning of this topic, you will recall that BorderBrush is the name of the xref:System.Windows.Media.SolidColorBrush that is assigned to the xref:System.Windows.Controls.Border.Background%2A of the xref:System.Windows.Controls.Border.

[!code-xamlVSMButtonTemplate#4]

The control is responsible for defining the states as part of its control contract, which is discussed in detail in Customizing Other Controls by Understanding the Control Contract later in this topic. The following table lists the states that are specified for the xref:System.Windows.Controls.Button.

VisualState Name VisualStateGroup Name Description
Normal CommonStates The default state.
MouseOver CommonStates The mouse pointer is positioned over the control.
Pressed CommonStates The control is pressed.
Disabled CommonStates The control is disabled.
Focused FocusStates The control has focus.
Unfocused FocusStates The control does not have focus.

The xref:System.Windows.Controls.Button defines two state groups: the CommonStates group contains the Normal, MouseOver, Pressed, and Disabled states. The FocusStates group contains the Focused and Unfocused states. States in the same state group are mutually exclusive. The control is always in exactly one state per group. For example, a xref:System.Windows.Controls.Button can have focus even when the mouse pointer is not over it, so a xref:System.Windows.Controls.Button in the Focused state can be in the MouseOver, Pressed, or Normal state.

You add xref:System.Windows.VisualState objects to xref:System.Windows.VisualStateGroup objects. You add xref:System.Windows.VisualStateGroup objects to the xref:System.Windows.VisualStateManager.VisualStateGroups%2A?displayProperty=nameWithType attached property. The following example defines the xref:System.Windows.VisualState objects for the Normal, MouseOver, and Pressed states, which are all in the CommonStates group. The xref:System.Windows.VisualState.Name%2A of each xref:System.Windows.VisualState matches the name in the preceding table. The Disabled state and the states in the FocusStates group are omitted to keep the example short, but they are included in the entire example at the end of this topic.

[!NOTE] Be sure to set the xref:System.Windows.VisualStateManager.VisualStateGroups%2A?displayProperty=nameWithType attached property on the root xref:System.Windows.FrameworkElement of the xref:System.Windows.Controls.ControlTemplate.

[!code-xamlVSMButtonTemplate#VisualStates]

The preceding example produces output that is similar to the following illustrations.

A button with a custom control template.
A button that uses a custom control template in the normal state

A button with a red border.
A button that uses a custom control template in the mouse over state

The border is transparent on a pressed button.
A button that uses a custom control template in the pressed state

To find the visual states for controls that are included with [!INCLUDETLA2#tla_winclient], see Control Styles and Templates.

Specifying the Behavior of a Control When It Transitions Between States

In the preceding example, the appearance of the button also changes when the user clicks it, but unless the button is pressed for a full second, the user does not see the effect. By default, the animation takes one second to occur. Because users are likely to click and release a button in much less time, the visual feedback will not be effective if you leave the xref:System.Windows.Controls.ControlTemplate in its default state.

You can specify the amount of time that it takes an animation to occur to smoothly transition a control from one state to another by adding xref:System.Windows.VisualTransition objects to the xref:System.Windows.Controls.ControlTemplate. When you create a xref:System.Windows.VisualTransition, you specify one or more of the following:

  • The time it takes for a transition between states to occur.

  • Additional changes in the control's appearance that occur at the time of the transition.

  • Which states the xref:System.Windows.VisualTransition is applied to.

Specifying the Duration of a Transition

You can specify how long a transition takes by setting the xref:System.Windows.VisualTransition.GeneratedDuration%2A property. The preceding example has a xref:System.Windows.VisualState that specifies that the button's border becomes transparent when the button is pressed, but the animation takes too long to be noticeable if the button is quickly pressed and released. You can use a xref:System.Windows.VisualTransition to specify the amount of time it takes the control to transition into the pressed state. The following example specifies that the control takes one hundredth of a second to go into the pressed state.

[!code-xamlVSMButtonTemplate#PressedTransition]

Specifying Changes to the Control's Appearance During a Transition

The xref:System.Windows.VisualTransition contains a xref:System.Windows.Media.Animation.Storyboard that begins when the control transitions between states. For example, you can specify that a certain animation occurs when the control transitions from the MouseOver state to the Normal State. The following example creates a xref:System.Windows.VisualTransition that specifies that when the user moves the mouse pointer away from the button, the button's border changes to blue, then to yellow, then to black in 1.5 seconds.

[!code-xamlVSMButtonTemplate#8]

Specifying When a VisualTransition Is Applied

A xref:System.Windows.VisualTransition can be restricted to apply to only certain states, or it can be applied any time the control transitions between states. In the preceding example, the xref:System.Windows.VisualTransition is applied when the control goes from the MouseOver state to the Normal state; in the example before that, the xref:System.Windows.VisualTransition is applied when the control goes into the Pressed state. You restrict when a xref:System.Windows.VisualTransition is applied by setting the xref:System.Windows.VisualTransition.To%2A and xref:System.Windows.VisualTransition.From%2A properties. The following table describes the levels of restriction from most restrictive to least restrictive.

Type of restriction Value of From Value of To
From a specified state to another specified state The name of a xref:System.Windows.VisualState The name of a xref:System.Windows.VisualState
From any state to a specified state Not set The name of a xref:System.Windows.VisualState
From a specified state to any state The name of a xref:System.Windows.VisualState Not set
From any state to any other state Not set Not set

You can have multiple xref:System.Windows.VisualTransition objects in a xref:System.Windows.VisualStateGroup that refer to the same state, but they will be used in the order that the previous table specifies. In the following example, there are two xref:System.Windows.VisualTransition objects. When the control transitions from the Pressed state to the MouseOver state, the xref:System.Windows.VisualTransition that has both xref:System.Windows.VisualTransition.From%2A and xref:System.Windows.VisualTransition.To%2A set is used. When the control transitions from a state that is not Pressed to the MouseOver state, the other state is used.

[!code-xamlVSMButtonTemplate#7]

The xref:System.Windows.VisualStateGroup has a xref:System.Windows.VisualStateGroup.Transitions%2A property that contains the xref:System.Windows.VisualTransition objects that apply to the xref:System.Windows.VisualState objects in the xref:System.Windows.VisualStateGroup. As the xref:System.Windows.Controls.ControlTemplate author, you are free to include any xref:System.Windows.VisualTransition you want. However, if the xref:System.Windows.VisualTransition.To%2A and xref:System.Windows.VisualTransition.From%2A properties are set to state names that are not in the xref:System.Windows.VisualStateGroup, the xref:System.Windows.VisualTransition is ignored.

The following example shows the xref:System.Windows.VisualStateGroup for the CommonStates. The example defines a xref:System.Windows.VisualTransition for each of the button's following transitions.

  • To the Pressed state.

  • To the MouseOver state.

  • From the Pressed state to the MouseOver state.

  • From the MouseOver state to the Normal state.

[!code-xamlVSMButtonTemplate#VisualTransitions]

Customizing Other Controls by Understanding the Control Contract

A control that uses a xref:System.Windows.Controls.ControlTemplate to specify its visual structure (by using xref:System.Windows.FrameworkElement objects) and visual behavior (by using xref:System.Windows.VisualState objects) uses the parts control model. Many of the controls that are included with [!INCLUDETLA2#tla_winclient] 4 use this model. The parts that a xref:System.Windows.Controls.ControlTemplate author needs to be aware of are communicated through the control contract. When you understand the parts of a control contract, you can customize the appearance of any control that uses the parts control model.

A control contract has three elements:

  • The visual elements that the control's logic uses.

  • The states of the control and the group each state belongs to.

  • The public properties that visually affect the control.

Visual Elements in the Control Contract

Sometimes a control's logic interacts with a xref:System.Windows.FrameworkElement that is in the xref:System.Windows.Controls.ControlTemplate. For example, the control might handle an event of one of its elements. When a control expects to find a particular xref:System.Windows.FrameworkElement in the xref:System.Windows.Controls.ControlTemplate, it must convey that information to the xref:System.Windows.Controls.ControlTemplate author. The control uses the xref:System.Windows.TemplatePartAttribute to convey the type of element that is expected, and what the name of the element should be. The xref:System.Windows.Controls.Button does not have xref:System.Windows.FrameworkElement parts in its control contract, but other controls, such as the xref:System.Windows.Controls.ComboBox, do.

The following example shows the xref:System.Windows.TemplatePartAttribute objects that are specified on the xref:System.Windows.Controls.ComboBox class. The logic of xref:System.Windows.Controls.ComboBox expects to find a xref:System.Windows.Controls.TextBox named PART_EditableTextBox and a xref:System.Windows.Controls.Primitives.Popup named PART_Popup in its xref:System.Windows.Controls.ControlTemplate.

[!code-csharpVSMButtonTemplate#ComboBoxContract] [!code-vbVSMButtonTemplate#ComboBoxContract]

The following example shows a simplified xref:System.Windows.Controls.ControlTemplate for the xref:System.Windows.Controls.ComboBox that includes the elements that are specified by the xref:System.Windows.TemplatePartAttribute objects on the xref:System.Windows.Controls.ComboBox class.

[!code-xamlVSMButtonTemplate#ComboBoxTemplate]

States in the Control Contract

The states of a control are also a part of the control contract. The example of creating a xref:System.Windows.Controls.ControlTemplate for a xref:System.Windows.Controls.Button shows how to specify the appearance of a xref:System.Windows.Controls.Button depending on its states. You create a xref:System.Windows.VisualState for each specified state and put all xref:System.Windows.VisualState objects that share a xref:System.Windows.TemplateVisualStateAttribute.GroupName%2A in a xref:System.Windows.VisualStateGroup, as described in Changing the Appearance of a Control Depending on Its State earlier in this topic. Third-party controls should specify states by using the xref:System.Windows.TemplateVisualStateAttribute, which enables designer tools, such as Expression Blend, to expose the control's states for authoring control templates.

To find the control contract for controls that are included with [!INCLUDETLA2#tla_winclient], see Control Styles and Templates.

Properties in the Control Contract

The public properties that visually affect the control are also included in the control contract. You can set these properties to change the appearance of the control without creating a new xref:System.Windows.Controls.ControlTemplate. You can also use the TemplateBinding markup extension to bind properties of elements that are in the xref:System.Windows.Controls.ControlTemplate to public properties that are defined by the xref:System.Windows.Controls.Button.

The following example shows the control contract for the button.

[!code-csharpVSMButtonTemplate#ButtonContract] [!code-vbVSMButtonTemplate#ButtonContract]

When creating a xref:System.Windows.Controls.ControlTemplate, it is often easiest to begin with an existing xref:System.Windows.Controls.ControlTemplate and make changes to it. You can do one of the following to change an existing xref:System.Windows.Controls.ControlTemplate:

Complete Example

The following example shows the complete xref:System.Windows.Controls.Buttonxref:System.Windows.Controls.ControlTemplate that is discussed in this topic.

[!code-xamlVSMButtonTemplate#3]

See Also

Styling and Templating