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1、Where C# Fits In出处：Professional C#Third Edition Simon RobinsonChristian NagelJay GlynnMorgan SkinnerKarli WatsonBill EvjenIn one sense, C# can be seen as being the same thing to programming languages as .NET is to the Windows environment. Just as Microsoft has been adding more and more features to W

2、indows and the Windows API over the past decade, Visual Basic and C+ have undergone expansion. Although Visual Basic and C+ have ended up as hugely powerful languages as a result of this, both languages also suffer from problems due to the legacies of how they have evolved.In the case of Visual Basi

3、c 6 and earlier, the main strength of the language was the fact that it was simple to understand and didnt make many programming tasks easy, largely hiding the details of the Windows API and the COM component infrastructure from the developer. The downside to this was that Visual Basic was never tru

4、ly object-oriented, so that large applications quickly become disorganized and hard to maintain. As well as this, because Visual Basics syntax was inherited from early versions of BASIC (which, in turn, was designed to be intuitively simple for beginning programmers to understand, rather than to wri

5、te large commercial applications), it didnt really lend itself to well-structured or object-oriented programs.C+, on the other hand, has its roots in the ANSI C+ language definition. It isnt completely ANSIcompliant for the simple reason that Microsoft first wrote its C+ compiler before the ANSI def

6、inition had become official, but it comes close. Unfortunately, this has led to two problems. First, ANSI C+ has its roots in a decade-old state of technology, and this shows up in a lack of support for modern concepts (such as Unicode strings and generating XML documentation), and in some archaic s

7、yntax structures designed for the compilers of yesteryear (such as the separation of declaration from definition of member functions). Second, Microsoft has been simultaneously trying to evolve C+ into a language that is designed for high-performance tasks on Windows, and in order to achieve that th

8、eyve been forced to add a huge number of Microsoft-specific keywords as well as various libraries to the language. The result is that on Windows, the language has become a complete mess. Just ask C+ developers how many definitions for a string they can think of: char*, LPTSTR, string, CString (MFC v

9、ersion), CString (WTL version), wchar_t*, OLECHAR*, and so on.Now enter .NETa completely new environment that is going to involve new extensions to both languages. Microsoft has gotten around this by adding yet more Microsoft-specific keywords to C+, and by completely revamping Visual Basic into Vis

10、ual Basic .NET, a language that retains some of the basic VB syntax but that is so different in design that we can consider it to be, for all practical purposes, a newlanguage. Its in this context that Microsoft has decided to give developers an alternativea language designed specifically for .NET,

11、and designed with a clean slate. Visual C# .NET is the result. Officially, Microsoft describes C# as a “simple, modern, object-oriented, and type-safe programming language derived fromC and C+. Most independent observers would probably change that to “derived from C, C+, and Java. Such descriptions

12、are technically accurate but do little to convey the beauty or elegance of the language. Syntactically, C# is very similar to both C+ and Java, to such an extent that many keywords are the same, and C# also shares the same block structure with braces () to mark blocks of code, and semicolons to sepa

13、rate statements. The first impression of a piece of C# code is that it looks quite like C+ or Java code. Behind that initial similarity, however, C# is a lot easier to learn than C+, and of comparable difficulty to Java. Its design is more in tune with modern developer tools than both of those other

14、 languages, and it has been designed to give us, simultaneously, the ease of use of Visual Basic, and the highperformance, low-level memory access of C+ if required. Some of the features of C# are: Full support for classes and object-oriented programming, including both interface and implementationi

15、nheritance, virtual functions, and operator overloading. A consistent and well-defined set of basic types. Built-in support for automatic generation of XML documentation. Automatic cleanup of dynamically allocated memory. The facility to mark classes or methods with user-defined attributes. This can

16、 be useful for documentationand can have some effects on compilation (for example, marking methods to becompiled only in debug builds). Full access to the .NET base class library, as well as easy access to the Windows API (if youreally need it, which wont be all that often). Pointers and direct memo

17、ry access are available if required, but the language has been designedin such a way that you can work without them in almost all cases. Support for properties and events in the style of Visual Basic. Just by changing the compiler options, you can compile either to an executable or to a library of.N

18、ET components that can be called up by other code in the same way as ActiveX controls(COM components). C# can be used to write ASP.NET dynamic Web pages and XMLWeb services.Most of the above statements, it should be pointed out, do also apply to Visual Basic .NET and Managed C+. The fact that C# is

19、designed from the start to work with .NET, however, means that its support for the features of .NET is both more complete, and offered within the context of a more suitable syntax thanfor those other languages. While the C# language itself is very similar to Java, there are some improvements:in part

20、icular, Java is not designed to work with the .NET environment.Before we leave the subject, we should point out a couple of limitations of C#. The one area the language is not designed for is time-critical or extremely high performance codethe kind where you really are worried about whether a loop t

21、akes 1,000 or 1,050 machine cycles to run through, and you need to clean up your resources the millisecond they are no longer needed. C+ is likely to continue to reign supreme among low-level languages in this area. C# lacks certain key facilities needed for extremely high performance apps, includin

22、g the ability to specify inline functions and destructors that are guaranteed to run at particular points in the code. However, the proportions of applications that fall into this category are very low.C#C#在某种程度上可以看作是.NET面向Windows环境的一种编程语言。在过去的十几年里，Microsoft给Windows和 Windows API添加了许多功能，VB和C+也经历了许多变化

23、。虽然VB和C+最终已成为非常强大的语言，但这两种语言也存在问题，因为它们保存了原来的一些内容。对于Visual Basic来说，它的主要优点是很容易理解，许多编程工作都很容易完成，根本上隐藏了Windows API和COM组件结构的内涵。其缺点是Visual Basic从来没有实现真正意义上的面向对象，所以大型应用程序很难分解和维护。另外，因为VB的语法继承于BASIC的早期版本(BASIC主要是为了让初学者更容易理解，而不是为了编写大型商业应用程序)，所以不能真正成为结构化或面向对象的编程语言。另一方面，C+在ANSI C+语言定义中有其自己的根。它与ANSI不完全兼容，因为Microso

24、ft是在ANSI定义标准化之前编写C+编译器的，但已经相当接近了。遗憾的是，这导致了两个问题。其一，ANSI C+是在十几年前的技术条件下开发的，因此不支持现在的概念(例如Unicode字符串和生成XML文档)，某些古老的语法结构是为以前的编译器设计的(例如成员函数的声明和定义是分开的)。其二，Microsoft同时还试图把C+演变为一种用于在Windows上执行高性能任务的语言 在语言中防止添加大量Microsoft专用的关键字和各种库。其结果是在Windows中，该语言成为了一种非常杂乱的语言。让一个C+开发人员说说字符串有多少个定义方式就可以说明这一点：char*、LPTSTR、stri

25、ng、CString (MFC 版本)、CString (WTL 版本)、wchar_t*和 OLECHAR*等。现在进入.NET时代 一种全新的环境，它对这两种语言都进行了新的扩展。Microsoft给C+添加了许多Microsoft专用的关键字，并把VB演变为VB.NET，保存了一些根本的VB语法，但在设计上完全不同，从实际应用的角度来看，VB.NET是一种新语言。在这里，Microsoft决定给开发人员另一个选择 专门用于.NET、具有新起点的语言， 即Visual C# .NET。Microsoft在正式场合把C#描述为一种简单、现代、面向对象、类型非常平安、派生于C和C+的编程语言。

26、大多数独立的评论员对其说法是“派生于C、 C+ 和Java。这种描述在技术上是非常准确的，但没有涉及到该语言的真正优点。从语法上看，C#非常类似于C+和Java，许多关键字都是相同的，C#也使用类似于C+和Java的块结构，并用括号()来标记代码块，用分号分隔各行语句。对C#代码的第一印象是它非常类似于C+或Java代码。但在这些外表上的类似性后面，C#学习起来要比C+容易得多，但比Java难一些。其设计与现代开发工具的适应性要比其他语言更高，它同时具有Visual Basic的易用性、高性能以及C+的低级内存访问性。C#包括以下一些特性： 完全支持类和面向对象编程，包括接口和继承、虚函数和运

27、算符重载的处理。 定义完整、一致的根本类型集。 对自动生成XML文档说明的内置支持。 自动清理动态分配的内存。 可以用用户定义的特性来标记类或方法。这可以用于文档说明，对编译有一定的影响(例如，把方法标记为只在调试时编译)。 对.NET基类库的完全访问权，并易于访问Windows API。 可以使用指针和直接内存访问，但C#语言可以在没有它们的条件下访问内存。 以VB的风格支持属性和事件。 改变编译器选项，可以把程序编译为可执行文件或.NET组件库，该组件库可以用与ActiveX控件(COM组件)相同的方式由其他代码调用。 C#可以用于编写ASP.NET动态Web页面和XML Web效劳。应该

28、指出，对于上述大多数特性，VB.NET和Managed C+也具备。但C#从一开始就使用.NET，对.NET特性的支持不仅是完整的，而且提供了比其他语言更适宜的语法。C#语言本身非常类似于Java，但其中有一些改良，因为Java并不是为应用于.NET环境而设计的。在结束这个主题前，还要指出C#的两个局限性。其一是该语言不适用于编写时间急迫或性能非常高的代码，例如一个要运行1000或1050次的循环，并在不需要这些循环时，立即清理它们所占用的资源。在这方面，C+可能仍是所有低级语言中的佼佼者。其二是C#缺乏性能极高的应用程序所需要的关键功能，包括保证在代码的特定地方运行的内联函数和析构函数。但这类应用程序非常少。出处：Professional C#Third Edition Simon RobinsonChristian NagelJay GlynnMorgan SkinnerKarli WatsonBill Evjen