Professional C# 6 and .NET Core 1.0. Christian Nagel

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      PART I

      The C# Language

      1

      .NET Application Architectures

      What’s In This Chapter?

      • Reviewing the history of .NET

      • Understanding differences between .NET Framework 4.6 and .NET Core 1.0

      • Assemblies and NuGet Packages

      • The Common Language Runtime

      • Features of the Windows Runtime

      • Programming Hello, World!

      • Universal Windows Platform

      • Technologies for creating Windows Apps

      • Technologies for creating Web Apps

      Wrox.com Code Downloads for This Chapter

      The wrox.com code downloads for this chapter are found at www.wrox.com/go/professionalcsharp6 on the Download Code tab. The code for this chapter is divided into the following major examples:

      • DotnetHelloWorld

      • HelloWorldApp (.NET Core)

Choosing Your Technologies

      In recent years,NET has become a huge ecosystem for creating any kind of applications on the Windows platform. With .NET you can create Windows apps, web services, web applications, and apps for the Microsoft Phone.

      The newest release of .NET is a big change from the last version – maybe the biggest change to .NET since its invention. Much of the .NET code has become open-source code, and you can create applications for other platforms as well. The new version of .NET (.NET Core) and NuGet packages allow Microsoft to provide faster update cycles for delivering new features. It’s not easy to decide what technology should be used for creating applications. This chapter helps you with that. It gives you information about the different technologies available for creating Windows and web applications and services, offers guidance on what to choose for database access, and highlights the differences between .NET and .NET Core.

Reviewing .NET History

      To better understand what is available with .NET and C#, it is best to know something about its history. The following table shows the version of .NET in relation to the Common Language Runtime (CLR), the version of C#, and the Visual Studio edition that gives some idea about the year when the corresponding versions have been released. Besides knowing what technology to use, it’s also good to know what technology is not recommended because there’s a replacement.

      The following sections cover the details of this table and the progress of C# and .NET.

      C# 1.0 – A New Language

      C# 1.0 was a completely new programming language designed for the .NET Framework. At the time it was developed, the .NET Framework consisted of about 3,000 classes and the CLR.

      After Microsoft was not allowed by a court order (filed by Sun, the company that created Java) to make changes to the Java code, Anders Hejlsberg designed C#. Before working for Microsoft, Hejlsberg had his roots at Borland where he designed the Delphi programming language (an Object Pascal dialect). At Microsoft he was responsible for J++ (Microsoft’s version of the Java programming language). Given Hejlsberg’s background, the C# programming language was mainly influenced by C++, Java, and Pascal.

      Because C# was created later than Java and C++, Microsoft analyzed typical programming errors that happened with the other languages, and did some things differently to avoid these errors. Some differences include the following:

      • With if statements, Boolean expressions are required (C++ allows an integer value here as well).

      • It’s permissible to create value and reference types using the struct and class keywords (Java only allows creating custom reference types; with C++ the distinction between struct and class is only the default for the access modifier).

      • Virtual and non-virtual methods are allowed (this is similar to C++; Java always creates virtual methods).

      Of course there are a lot more changes as you’ll see reading this book.

      At this time, C# was a pure object-oriented programming language with features for inheritance, encapsulation, and polymorphism. C# also offered component-based programming enhancements such as delegates and events.

      Before the existence of .NET with the CLR, every programming language had its own runtime. With C++, the C++ Runtime is linked with every C++ program. Visual Basic 6 had its own runtime with VBRun. The runtime of Java is the Java Virtual Machine – which can be compared to the CLR. The CLR is a runtime that is used by every .NET programming language. At the time the CLR appeared on the scene, Microsoft offered JScript.NET, Visual Basic .NET, and Managed C++ in addition to C#. JScript.NET was Microsoft’s JavaScript compiler that was to be used with the CLR and .NET classes. Visual Basic.NET was the name for Visual Basic that offered .NET support. Nowadays it’s just called Visual Basic again. Managed C++ was the name for a language that mixed native C++ code with Managed .NET Code. The newer C++ language used today with .NET is C++/CLR.

      A compiler for a .NET programming language generates Intermediate Language (IL) code. The IL code looks like object-oriented machine code and can be checked by using the tool ildasm.exe to open DLL or EXE files that contain .NET code. The CLR contains a just-in-time (JIT) compiler that generates native code out of the IL code when the program starts to run.

      NOTE IL code is also known as managed code.

      Other parts of the CLR are a garbage collector (GC), which is responsible for cleaning up managed memory that is no longer referenced; a security mechanism that uses code access security to verify what code is allowed to do; an extension for the debugger to allow a debug session between different programming languages (for example, starting a debug session with Visual Basic and continuing to debug within a C# library); and a threading facility that is responsible for creating threads on the underlying platform.

      The .NET Framework was already huge with version 1. The classes are organized within namespaces to help facilitate navigating the 3,000 available classes. Namespaces are used to group classes and to solve conflicts by allowing the same class name in different namespaces. Version 1 of the .NET Framework allowed creating Windows desktop applications using Windows Forms (namespace System.Windows.Forms), creating web applications with ASP.NET Web Forms (System.Web), communicating with applications and web services using ASP.NET Web Services, communicating more quickly between .NET applications using .NET Remoting, and creating COM+ components for running in an application server using Enterprise Services.

      ASP.NET Web Forms was the technology for creating web applications with the goal for the developer to not need to know something about HTML and JavaScript. Server-side controls that worked similarly to Windows Forms itself created HTML and JavaScript.

      C#