XAML

XAML: Extensible Application Markup Language

XAML, short for eXtensible Application Markup Language, is a descriptive language created by Microsoft to build user interfaces for applications. XAML provides syntax that separates UI design from program logic, much like the code-behind model in ASP.NET. While XAML is a markup language that can be parsed, it can also be compiled. Its primary advantage lies in simplifying the process of creating user interfaces by reducing the amount of programming effort required for design and configuration.

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Overview

XAML allows developers and designers to work in tandem by splitting responsibilities. Developers focus on back-end program logic, while designers concentrate on the visual aspects of the UI. This separation fosters smoother collaboration and leverages the expertise of both parties.

Pronounced as "Zamel," XAML may seem daunting due to its new rules, elements, and syntax, but anyone with basic knowledge of HTML can quickly grasp its concepts.

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Advantages

1. Simplifies UI Creation:
   
   XAML streamlines the process of creating user interfaces in the .NET Framework 3.0, particularly for WPF (Windows Presentation Foundation) applications. Developers can fully customise UI elements such as text, buttons, images, and list boxes, and arrange them in a structured layout similar to HTML.

2. XML-based Structure:
   
   Since XAML is XML-based, it is a well-organized document with stricter and clearer syntax than HTML. Most XAML code can eventually be auto-generated by tools, much like modern static web pages can be built without directly writing HTML. However, manually writing XAML is an excellent way to gain a deeper understanding of its syntax and elements.

3. Flexible Integration:
   
   While WPF applications can include both program code and XAML, developers can choose to define the UI in XAML and implement functionality through separate logic files. Although everything in XAML can technically be implemented with programming code, XAML excels in building and describing user interfaces, while programming languages like C# are better suited for handling logic and processing flows.

4. Strong Typing:
   
   Unlike HTML, which ignores unrecognized elements, XAML is strongly typed and requires all elements and attributes to be recognized by the framework for proper rendering. This ensures that XAML-defined elements directly map to WPF objects.

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Not HTML

Despite similarities in element declaration, style settings, and event handler specifications, XAML is not HTML. XAML is an XML-based language designed for WPF and focuses on presenting information and handling advanced UI features such as animation and 3D rendering. Unlike HTML, which is primarily for rendering browser-based content, XAML supports extensibility, allowing developers to create custom controls, elements, and functions. These can be easily reused or shared with designers and other developers.

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XAML and WPF in .NET Framework 3.0

XAML is a core part of Windows Presentation Foundation (WPF), which is a subset of Microsoft’s .NET Framework 3.0. WPF enables rich client-side application development for both Windows and web browsers. WPF-based applications can run on Windows Vista or earlier Windows versions that have .NET Framework 3.0 (and Internet Explorer 7.0 for browser-based apps) installed.

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Applications

With XAML, developers can create highly detailed UI documents by defining controls, text, images, animations, and more, without requiring programming code for basic UI configurations. However, for runtime logic or dynamic functionality, developers must add code. The UI design and logic are stored in separate files, allowing seamless collaboration between developers and designers.

In applications like Silverlight, XAML serves multiple roles:

1. UI Declaration:
   
   XAML files define the application's primary UI and support navigation or modal replacements. They can also define reusable resources like templates.

2. Styling and Templates:
   
   Developers can template existing controls or provide default templates for new controls.

3. Designer Interoperability:
   
   XAML files can be exchanged between tools like Expression Blend and Visual Studio, simplifying collaboration.

4. Cross-Platform UI Migration:
   
   XAML provides a smooth transition between Silverlight and WPF projects, leveraging shared namespaces and vocabulary subsets.

5. Separation of Concerns:
   
   XAML defines the visual interface, while its associated code-behind file handles the logic. This separation streamlines workflows between designers and developers.

6. Rapid Prototyping:
   
   XAML facilitates quick UI prototyping in early development stages. Even after significant visual redesigns, the code remains accessible for further development.

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Code and Tools

In tools like Expression Blend, XAML is stored in .xaml files, while the associated logic resides in files with the same name but .cs (C#) or .vb (Visual Basic) extensions. For example, a XAML file named Window1.xaml would have its logic stored in Window1.xaml.cs if the programming language is C#.

The WPF parser reads .xaml files to generate the UI, reporting any errors during project build or file editing. Errors are displayed in the “Results” panel and must be resolved before rendering.

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Collaborative Tools

Artistic resources can be exported as XAML from tools like Microsoft Expression Design and imported into Expression Blend for use in projects. Other tools are available online for converting graphical assets into XAML.

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