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The .NET Framework is an integral Microsoft Windows component designed to support next-generation applications and services. Many fundamentals of the .NET Framework will be familiar to developers who have worked in other object-oriented development environments; however, the .NET Framework also includes many unique elements that will be new to even the most experienced developers. This chapter provides an overview of .NET Framework programming, including knowledge required for every other chapter in this book.

If you have worked with versions of the .NET Framework released prior to version 2.0, much of this will be familiar. However, version 2.0 of the .NET Framework includes several new features: generics, partial classes, and type forwarding (all described in Lesson 3, Constructing Classes ).

Exam objectives in this chapter:

Manage data in a .NET Framework application by using the .NET Framework 2.0 system types. (Refer System namespace)

Value types Reference types Attributes Generic types Exception classes Boxing and UnBoxing TypeForwardedToAttribute Class

Implement .NET Framework interfaces to cause components to comply with standard contracts. (Refer System namespace)

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Control interactions between .NET Framework application components by using events and delegates. (Refer System namespace)

Lessons in this chapter:

Lesson 1: Using Value Types . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 Lesson 2: Using Common Reference Types . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17 Lesson 3: Constructing Classes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32 Lesson 4: Converting Between Types. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 54

This book assumes that you have at least two to three years of experience developing Web-based, Microsoft Windows-based, or distributed applications by using the .NET Framework 1.0, the .NET Framework 1.1, and the .NET Framework 2.0. Candidates should have a working knowledge of Microsoft Visual Studio 2005. Before you begin, you should be familiar with Microsoft Visual Basic or C# and be comfortable with the following tasks:

Create a console or Windows Forms application in Visual Studio using Visual Basic or C#. Add namespaces and references to system class libraries to a project. Run a project in Visual Studio, set breakpoints, step through code, and watch the values of variables.

The simplest types in the .NET Framework, primarily numeric and Boolean types, are value types. Value types are variables that contain their data directly instead of containing a reference to the data stored elsewhere in memory. Instances of value types are stored in an area of memory called the stack, where the runtime can create, read, update, and remove them quickly with minimal overhead.

There are three general value types:

Each of these types is derived from the System.Value base type. The following sections show how to use these different types.

After this lesson, you will be able to:

Choose the most efficient built-in value type Declare value types Create your own types Use enumerations

Built-in types are base types provided with the .NET Framework, with which other types are built. All built-in numeric types are value types. You choose a numeric type based on the size of the values you expect to work with and the level of precision you require. Table 1-1 lists the most common numeric types by size, from smallest to largest. The first six types are used for whole number values and the last three represent real numbers in order of increasing precision.