Software Programs and Projects

Introduction to Windows Presentation Foundation


The Windows Presentation Foundation is Microsofts next generation UI framework to create applications with a rich user experience. It is part of the .NET framework 3.0 and higher.

WPF combines application UIs, 2D graphics, 3D graphics, documents and multimedia into one single framework. Its vector based rendering engine uses hardware acceleration of modern graphic cards. This makes the UI faster, scalable and resolution independent.

Separation of Appearance and Behavior

WPF separates the appearance of an user interface from its behavior. The appearance is generally specified in the Extensible Application Markup Language (XAML), the behavior is implemented in a managed programming language like C# or Visual Basic. The two parts are tied together by databinding, events and commands. The separation of appearance and behavior brings the following benefits:

* Appearance and behaviour are loosely coupled
* Designers and developers can work on separate models.
* Graphical design tools can work on simple XML documents instead of parsing code.

Programming with WPF

WPF exists as a subset of .NET Framework types that are for the most part located in the System.Windows namespace. If you have previously built applications with .NET Framework using managed technologies like ASP.NET and Windows Forms, the fundamental WPF programming experience should be familiar; you instantiate classes, set properties, call methods, and handle events, all using your favorite .NET Framework programming language, such as C# or Visual Basic.

To support some of the more powerful WPF capabilities and to simplify the programming experience, WPF includes additional programming constructs that enhance properties and events: dependency properties and routed events. For more information on dependency properties, see Dependency Properties Overview. For more information on routed events, see Routed Events Overview.
Markup and Code-Behind

WPF offers additional programming enhancements for Windows client application development. One obvious enhancement is the ability to develop an application using both markup and code-behind, an experience that ASP.NET developers should be familiar with. You generally use Extensible Application Markup Language (XAML) markup to implement the appearance of an application while using managed programming languages (code-behind) to implement its behavior. This separation of appearance and behavior has the following benefits:

* Development and maintenance costs are reduced because appearance-specific markup is not tightly coupled with behavior-specific code.

* Development is more efficient because designers can implement an application's appearance simultaneously with developers who are implementing the application's behavior.

* Multiple design tools can be used to implement and share XAML markup, to target the requirements of the application development contributors; Microsoft Expression Blend provides an experience that suits designers, while Visual Studio 2005 targets developers.

* Globalization and localization for WPF applications is greatly simplified (see WPF Globalization and Localization Overview).

The following is a brief introduction to WPF markup and code-behind. For more information on this programming model, see XAML Overview (WPF) and Code-Behind and XAML in WPF.



tag:-Introduction to Windows Presentation Foundation

Introduction to XAML

XAML stands for Extensible Application Markup Language. Its a simple language based on XML to create and initialize .NET objects with hierarchical relations. Altough it was originally invented for WPF it can by used to create any kind of object trees.

Today XAML is used to create user interfaces in WPF, Silverlight, declare workflows in WF and for electronic paper in the XPS standard.

All classes in WPF have parameterless constructors and make excessive usage of properties. That is done to make it perfectly fit for XML languages like XAML.
Advantages of XAML

All you can do in XAML can also be done in code. XAML ist just another way to create and initialize objects. You can use WPF without using XAML. It's up to you if you want to declare it in XAML or write it in code. Declare your UI in XAML has some advantages:

• XAML code is short and clear to read
• Separation of designer code and logic
• Graphical design tools like Expression Blend require XAML as source.
• The separation of XAML and UI logic allows it to clearly separate the roles of designer and developer.

LINQ is a set of extensions to the .NET Framework that encompass language-integrated query, set, and transform operations. It extends C# and Visual Basic with native language syntax for queries and provides class libraries to take advantage of these capabilities.

We use the term language-integrated query to indicate that query is an integrated feature of the developer's primary programming languages (for example, Visual C#, Visual Basic). Language-integrated query allows query expressions to benefit from the rich metadata, compile-time syntax checking, static typing and IntelliSense that was previously available only to imperative code. Language-integrated query also allows a single general purpose declarative query facility to be applied to all in-memory information, not just information from external sources.

.NET Language-Integrated Query defines a set of general purpose standard query operators that allow traversal, filter, and projection operations to be expressed in a direct yet declarative way in any .NET-based programming language. The standard query operators allow queries to be applied to any IEnumerable-based information source. LINQ allows third parties to augment the set of standard query operators with new domain-specific operators that are appropriate for the target domain or technology. More importantly, third parties are also free to replace the standard query operators with their own implementations that provide additional services such as remote evaluation, query translation, optimization, and so on. By adhering to the conventions of the LINQ pattern, such implementations enjoy the same language integration and tool support as the standard query operators.

The extensibility of the query architecture is used in the LINQ project itself to provide implementations that work over both XML and SQL data. The query operators over XML (LINQ to XML) use an efficient, easy-to-use, in-memory XML facility to provide XPath/XQuery functionality in the host programming language. The query operators over relational data (LINQ to SQL) build on the integration of SQL-based schema definitions into the common language runtime (CLR) type system. This integration provides strong typing over relational data while retaining the expressive power of the relational model and the performance of query evaluation directly in the underlying store.


Example :

using System;
using System.Linq;
using System.Collections.Generic;

class app {
  static void Main() {
    string[] names = { "Burke", "Connor", "Frank", 
                       "Everett", "Albert", "George", 
                       "Harris", "David" };

    IEnumerable query = from s in names 
                               where s.Length == 5
                               orderby s
                               select s.ToUpper();

    foreach (string item in query)
      Console.WriteLine(item);
  }
}


The local variable query is initialized with a query expression.A query expression operates on one or more information sources by
applying one or more query operators from either the standard query operators or domain-specific operators. This expression uses three of
the standard query operators: Where, OrderBy, and Select.