【正文】 wever, we generalize and refer to them both as functions. Functions can have four kinds of parameters: ? Input parameters have values that are sent into the function, but the function cannot change those values. ? Output parameters have no value when they are sent into the function, but the function can give them a value and send the value back to the caller. ? Reference parameters pass in a reference to another value. They have a value ing in to the function, and that value can be changed inside the function. ? Params parameters define a variable number of arguments in a list. C and the CLR work together to provide automatic memory management. You don39。t define a variable outside of a class, and you can39。ll learn more about objects in Chapter 8, Writing ObjectOriented Code. For now, think of an object as a collection of data and a set of operations that can be performed on that data. Objectstyle coding could be acplished using C, but the notion of an object was not enforced by the language. If you wanted to structure your code to resemble an object, fine. If you didn39。允許 .NET結(jié)構(gòu)的 JIT編譯器核實(shí)你的代碼以確保你的代碼通過(guò)一個(gè)漏洞很大的路徑訪問(wèn)內(nèi)存并且變量類型會(huì)被正確地使用。 另外一個(gè)編譯器使用 MSIL的原因是指令的設(shè)置能夠很容易地被一個(gè)認(rèn)證近程讀取。非常有可能的是這兩種設(shè)備有著不同的 CPU。那么，當(dāng)你的 CPU不能讀取 MSIL的時(shí)候，說(shuō)明代碼中。 微軟中間語(yǔ)言（ MSIL） 被 C編譯器輸出的代碼是寫在一種叫做微軟中間語(yǔ)言中的。如果我們使用一個(gè)接口在這個(gè)例子中，你的 DLL添加項(xiàng)可以應(yīng)用于一個(gè)接口。要做這些，這個(gè)添加項(xiàng)必須遵守 一些規(guī)則。 接口 C提供了接口，它聚集了屬性，方法，和闡述一套功能的事件。 C提供了一個(gè)嵌入式的機(jī)制去定義和處理一些事件。 類能夠包含代碼和數(shù)據(jù)。 ? 參數(shù)參數(shù)在列表中定義了一個(gè)數(shù)組變量。如果雇員的名字必須被一個(gè)數(shù)據(jù)庫(kù)讀，例如，你可以寫一個(gè)代碼 “當(dāng)一些人詢問(wèn)名字屬性的值時(shí)，從數(shù)據(jù)庫(kù)中讀名字，并且返回這個(gè)名字用 string類型” 函數(shù) 一個(gè)函數(shù)是一種可以隨時(shí)使用的代碼，代碼。 你可以同時(shí)使用單維和多維的數(shù)組在 C中。引用類型保存實(shí)際的值儲(chǔ)存在存儲(chǔ)器別處的位置。 } 注：?jiǎn)卫^承意味著一個(gè) C類只能從一個(gè)基類中繼承。類提供了單繼承，所有的類最終從基類獲取的東西就是對(duì)象。因此它能夠保持前輩的強(qiáng)項(xiàng)并且丟棄使得 C和 C++程序生存困難的弱點(diǎn) 2. 引進(jìn) C C這門在 .NET體系中被引進(jìn)的全新語(yǔ)言，是從 C++衍生出來(lái)的。被設(shè)定的目標(biāo)是保持對(duì)C的兼容， C++不能夠打破 C的底層特性。對(duì)象并不是一個(gè)固有的部分在這門語(yǔ)言中，很多人并沒(méi)有花很大的經(jīng)歷在這個(gè)程序示例中。 C程序語(yǔ)言原本是被定義在 UNIX操作系統(tǒng)中的。這部分觀看 C和 C++，在 C中追蹤它們的發(fā)展。如果你不想這么做， C也確實(shí)不會(huì)介意。和C++可以處理在一些非常給力的應(yīng)用程序中，碼工作的很流暢。 C正在開(kāi)始一個(gè)清潔的石板并且沒(méi)有任何兼容需求。當(dāng)類的對(duì)象被釋放時(shí)，類也就被銷毀了。 public string FullName() { } return FirstName + LastName。值類型保存實(shí)際的值。 前后引用 參考第三章“同變 量一起工作”來(lái)找到更多的關(guān)于顯式和隱式轉(zhuǎn)換策略的信息。碼賦值之后什么應(yīng)該發(fā)生。它們有一個(gè)值進(jìn)入函數(shù)，并且這個(gè)值可以在函數(shù)中被更改。通過(guò)報(bào)表的操作，使用關(guān)鍵字，就像 switch,while,for,break和 continue能夠使你的代碼根據(jù)變量值的不同分入到不同的路徑中。如果你使用一個(gè)變量去表示行星的時(shí)候，用這個(gè)枚舉類型的 names可以使你的代碼變的更易讀。你可以寫一個(gè)分度器在你的 Rainbow類中來(lái)定義什么將會(huì)被返回當(dāng)這個(gè)訪問(wèn) 者訪問(wèn)你的類時(shí)，就好像它是一個(gè)值的數(shù)組。執(zhí)行的時(shí)候有讀取添加項(xiàng)的能力。這種創(chuàng)建讀取添加項(xiàng)是必要的，因?yàn)樗鼡?dān)負(fù)了更多的不必要的代碼責(zé)任。接下來(lái)的部分描述了這兩種主題并 且完成了建立在 .NET代碼上的一塊二進(jìn)制的審查，那就是匯編。它不知道任何關(guān)于你機(jī)器 CPU的事，同樣的你的機(jī)器也不知道任何有關(guān) MSIL的事。假設(shè)你已經(jīng)寫了一些 C代碼，并且你想讓它同時(shí)運(yùn)行在你的臺(tái)式機(jī)和手提設(shè)備上。 你現(xiàn)在僅僅有一個(gè)可以運(yùn)行在任何擁有 .NET JIT編譯器的設(shè)備上的 MSIL基本代碼在這些設(shè)備上的 JIT編譯器能夠照顧你的代碼使他們運(yùn)行的很順利。有一個(gè)可以立刻輸出 CPU特定代碼的 C編譯器能夠使代碼的檢查很困難或者甚至不可能。t be said for C and C++, but because C was created from the ground up, Microsoft took the liberty of removing some of the more burdensome features — such as pointers. This section takes a look at the C and C++ languages, tracing their evolution into C. The C programming language was originally designed for use on the UNIX operating system. C was used to create many UNIX applications, including a C piler, and was eventually used to write UNIX itself. Its widespread acceptance in the academic arena expanded to include the mercial world, and software vendors such as Microsoft and Borland released C pilers for personal puters. The original Windows API was designed to work with Windows code written in C, and the latest set of the core Windows operating system APIs remain patible with C to this day. From a design standpoint, C lacked a detail that other languages such as Smalltalk had already embraced: the concept of an object. You39。t worry. All of them are covered in detail in later chapters. Classes All code and data in C must be enclosed in a class. You can39。s name by writing . Properties are like fields, but enable you to write code to specify what should happen when code accesses the value. If the employee39。ve written some C code and you39。re going to want to make use of some alreadypiled .NET code. That code may be supplied by Microsoft as a part of Framework, or it may be supplied by a user over the Inter. The key to using this external code is letting the C piler know what classes and variables are in the other code base so that it can match up the source code you write with the code found in the prepiled code base that you39。re familiar with Microsoft Transaction Server or COM+, you can think of an assembly as the .NET equivalent of a package. There are two types of assemblies: private assemblies and global assemblies. When you build your assembly, you don39。t want to build an entire application. Instead, you may want to build a code library that can be used by others. You may also want to build some utility classes in C, for example, and then hand the code off to a Visual Bas ic .NET developer, who will use your classes in a Visual Basic .NET application. In cases like this, you won39。d have to pile your code twice, ensuring that you put the right code on the right device. With MSIL, you pile once. Installing the .NET Framework on your desktop machine includes a JIT piler that translates your MSIL into CPUspecific code for your desktop. Installing the .NET Framework on your handheld includes a JIT piler that translates that same MSIL into CPUspecific code for your handheld. You now have a single MSIL code base that can run on any device that has a .NET JIT piler. The JIT piler on that device takes care of making your code run on the device. Another reason for the piler39。t be changing as your code runs. Enum type declarations specify a type name for a related group of constants. For example, you could define an enum of Plas with values of Mercury, V those names in your code. Using the enum names in code makes code more readable than if you used a number to represent each pla. C provides a builtin mechanism for d