Lập trình .net 4.0 và visual studio 2010 part 58 potx

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Input Bindings Now Support Bindings
In previous releases of WPF, it was quite tricky to set binding to input keys using the InputBinding class.
This was because the Command property was not a dependency property and also didn’t inherit the
parent's data context. This could make certain scenarios such as implementing the MVVM pattern
difficult.
This is resolved in WPF 4.0. InputBinding, MouseBinding, and KeyBinding now inherit from Freezable
and various related properties are now made dependency properties. This should then allow you to
write input binding XAML such as the following:

<Window.InputBindings>
<KeyBinding
Modifiers="Control" Key="L"
Command="{Binding MyCustomCommand}" />
</Window.InputBindings>
Text-Rendering Improvements
In previous releases of WPF, text could sometimes appear a bit blurry. This is fixed in WPF 4.0 (possibly
driven by the need for clear text in VS2010 IDE) and you now have much finer-grained control over how
text is rendered with the new TextFormattingMode and TextRenderingMode properties.
TextOptions.TextFormattingMode
TextFormatting mode allows you to set the text metrics that WPF will use for formatting text.
TextFormatting mode has two settings:
• Ideal (as per previous versions)
• Display (ensures that every glyph’s position and width is not fractional, which is
very similar to how the GDI renders text)
The following code demonstrates setting text to use the Display setting:

<TextBlock TextOptions.TextFormattingMode="Display">
Hello I am using new Display mode formatting

</TextBlock>

Setting text to Display mode will in many cases make the text look darker and clearer. In Figure 15-
20 the first paragraph uses the old Ideal setting; the second uses the new Display setting (yes, the
difference is subtle, especially in print, but try it for yourself).

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Figure 15-20. Display mode property
Ideal mode works well for situations when you have large fonts or perform transformations/zoom
into the text but can look a bit blurry at small font sizes. In these cases you would probably be better off
using the Display setting.
TextOptions.TextRenderingMode
The TextRendering setting, which allows you to control how text is anti-aliased, has four settings:
• Auto (uses clear type unless disabled)
• Aliased (disables anti-aliasing)
• Grayscale (uses grayscale anti-aliasing)
• Cleartype (uses clear type anti-aliasing)
The following code shows how to apply the Grayscale rendering mode:

<TextBlock TextOptions.TextRenderingMode="Grayscale">
I am rendered using Grayscale
</TextBlock>

Figure 15-21 shows how these settings effect the output.

Figure 15-21. Demonstration of TextRendering setting
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Microsoft recommends that for most scenarios Auto is the best setting to use because it takes
advantage of ClearType where available.
RenderOptions.ClearTypeHint
In some rendering situations (such as rendering on transparent areas), ClearType functionality will be
disabled and Grayscale rendering will be used. This can result in text that is not as sharp as it could be.
WPF 4.0 contains a new option called ClearTypeHint to force applications to utilize ClearType. The
following code illustrates how to apply this to a TextBlock:

<TextBlock RenderOptions.ClearTypeHint="Enabled">

I will use cleartype

</TextBlock>

East Asian Bitmap font support
Some non-English alphabet characters can be quite complex (think Chinese glyphs), and when rendered
at smaller sizes can appear very blurry using vector transformations. WPF now uses bitmaps for smaller
text size (if available) which can result in crisper text. Microsoft say this feature is supported for the
following languages and fonts such as:
• Japanese (MS Gothic)
• Korean (Gulium)
• Korean (Batang)
• Traditional Chinese (MingLiu)
• Simplified Chinese (SimSun)
Layout Rounding
When positioning elements in WPF you can sometimes end up with fractional values. For example,
splitting a grid 100 pixels wide into 3 columns of equal size gives each column a nasty width of
33.333333. These fractional properties can result in images and objects with blurry edges and other

horrid rendering artifacts. To see many examples, see this excellent site that visually demonstrates the
affects of subpixel layouts:
Silverlight 2.0 introduced a new property called UseLayoutRounding that offers a solution to this issue
by forcing the layout to use whole pixel values only. UseLayoutRouting is now supported in WPF. Using
this feature can result in crisper images and layouts, but your layout might not be pixel perfect. This
XAML demonstrates how to use this property:

<Grid UseLayoutRounding="True" >
</Grid>
Cached Composition
Arguably one of the best additions to WPF 4.0 is cached composition, that allows you to cache any part
of the visual tree. Complex effects can take time to render, which results in a jerky experience for your
users and uses vast amounts of CPU and memory. WPF 4.0 allows you to cache elements as a bitmap,
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reducing this rendering time and resource usage with the new BitmapCache and BitmapCacheBrushes
classes. The BitmapCacheBrushes class is used when you will reuse the same content multiple times.
Cached composition supports dirty regions, so it is clever enough to re-render only the parts that
have changed. Re-rendering can occur when WPF detects the visual tree changes or any cache-related
properties are modified. Note that the maximum dimensions the bitmap cache supports are 2048 by
2048 pixels.
There is an excellent demo by Lester Lobo that shows the difference cached composition can make:

new-wpf-features-cached-composition.aspx.
CacheMode can be turned on with the following XAML (applied to a Canvas element in this example):

<Canvas.CacheMode>
<BitmapCache />
</Canvas.CacheMode>

<Canvas x:name="myCanvas" CacheMode="BitmapCache"/>

Or programmatically:

myCanvas.CacheMode = new BitmapCache();

And turned off with the following code:

myCanvas.CacheMode = null;
Animation Easing
WPF contains new effects for creating nonlinear movements using complex mathematical formulas to
produce effects such as bouncy spring animations. You will look at how to utilize these in Silverlight 3.0
later in the chapter, but know that WPF 4.0 provides the following effects:
• BackEase
• BounceEase
• CircleEase
• CubicEase
• Elasticease
• ExponentialEase
• Quadraticease
• QuarticEase
• Quinticease
• PowerEase
• SineEase
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Pixel Shader 3.0 Support
Previous releases of WPF supported Pixel Shaders version 2.0. WPF 4.0 now supports Pixel Shader
version 3.0. Note that the hardware the application is running on must also support the Pixel Shader

capabilities. To query this, use the static methods on the RenderCapability class such as
RenderCapability.IsPixelShaderVersionSupported.
Visual State Manager Integration
Visual State Manager (VSM)) allows you to define a set of states for your controls (e.g., normal, mouse
over, mouse down) and then define a different look for each of these states. VSM will automatically
animate the transitions between states; for example, if you have a black button with a mouse down state
that highlights it blue, the button can gradually be highlighted blue as the user hovers the mouse. In
WPF 4.0, the VisualStateManager and related classes are added to the main framework.
HTML-XBAP Script Interop
HTML-XBAP applications can use the new BrowserInteropHelper class to interact with the hosting web
page. BrowserInteropHelper provides full DOM access and can handle DOM events.
Full-Trust XBAP Deployment
In previous releases of WPF, it was quite difficult to create a fully trusted XBAP application. That changes
with this release; XBAP applications that require full trust that are run from intranet or trusted site zones
will now give users the ClickOnce elevation prompt. This allows users to easily grant the necessary
privileges for your application.
Client Profile
It is worth mentioning the client profile (a cut-down version of the full .NET Framework) aimed at
reducing application size and installation time is also used for WPF applications. For more information
about the client profile, please refer to Chapter 4.
Miscellaneous Changes
You have barely touched the surface with all the new functionality available in WPF 4 but4.0 before you
leave this area I would like to mention a number of other additions that were made:
• New XAML parser
• Many additions to XAML 2009 language such as support for Generics
• RichTextBox now supports custom dictionaries rather than just using the OS-
provided dictionary ( />dictionaries.aspx)
• Text selection can be customized for TextBox, RichTextBox,
FlowDocumentPageViewer, FlowDocumentScrollViewer, FlowDocumentReader, and
PasswordBox with the new Selection Brush API

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• Many changes to API and refactoring of XamlSchemaContext for performance
improvements
• System.Xaml.dll no longer has a dependency on WindowsBase.dll
• The same XAML stack is utilized by WCF, WF, and WPF
• Performance optimizations in Baml2006Reader class
• New class XamlXmlReader
• Improved localization support
• Baml2006Writer class might be available with this release, which could potentially
allow the obfuscation of BAML
Silverlight 3.0

Silverlight developers are in for a treat with the latest version of Silverlight which offers the ability to run
your applications offline, deep linking for content and much more.

NOTE
This chapter assumes a basic knowledge of Silverlight and WPF. If you haven’t used Silverlight before
you might want to take a look at Chapter 14 where I introduce Silverlight.
Upgrading from Silverlight 2
Before you look at the new changes in Silverlight 3.0, note that upgrading can potentially break existing
applications. This URL lists breaking changes: />us/library/cc645049(VS.95).aspx.
And this URL provides guidance on how to upgrade your Silverlight 2.0 applications:

Offline Applications
Probably the best feature of Silverlight 3.0 is the ability it offers to run your applications offline. Offline
Silverlight applications run with the same permissions as their web counterparts, so they do not require
additional permissions to install. Offline applications also work on both PC and Mac platforms,
providing a very easy way to create cross-platform .NET applications.

Creating an Offline Application
To enable your Silverlight applications to run offline is very easy and involves making a simple change to
the AppManifest file. Try it now:
1. Create a new Silverlight application called Chapter15.Offline.
2. Add some content (e.g., an image).