[译]C#编码约定

原文:https://msdn.microsoft.com/en-us/library/ff926074.aspx

编码约定的目的是:

  • 创建统一格式的代码,让读者的注意力更集中在内容上面,而不是结构

  • 让读者基于以前的经验能更快的理解代码

  • 使得copy, 修改, 维护代码更加便利

  • 演示C#最佳实践

命名约定

  • In short examples that do not include using directives, use namespace qualifications. If you know that a namespace is imported by default in a project, you do not have to fully qualify the names from that namespace. Qualified names can be broken after a dot (.) if they are too long for a single line, as shown in the following example.

    var currentPerformanceCounterCategory = new System.Diagnostics.
    PerformanceCounterCategory();
  • 不应该修改vs设计工具生成的对象的名字。

布局约定

好的布局格式化强调你代码的结构,让代码更易读。Microsoft的一些实例代码遵循下面的约定:

  • 使用默认代码编辑器的设置 (smart缩进, 四个字符缩进, tab用空格代替)。详见Options, Text Editor, C#, Formatting

  • 一行只写一个语句。

  • 一行只有一个声明的变量。

  • 如果一个连续的行没有自动缩进,那么使用tab缩进 (4个空格)。

  • 在方法的定义之间和属性定义之间至少添加一个空行。

  • 使用括号把子表达式括起来,如下所示。

    if ((val1 > val2) && (val1 > val3))
    {
    // Take appropriate action.
    }

注释约定

  • 在单独的一行添加注释,不要在代码的最后写注释。

  • 注释文本以大写开头(首字母大写)。

  • 注释文本以句号结尾。

  • 注释符(//)和注释文本中留一个空格,如下所示。

    // The following declaration creates a query. It does not run
    // the query.
  • 不用星号多行注释。

语言指南

下面的章节展示了C#团队在写样例代码的时候所遵循的约定。

String Data Type

  • 使用+号连接短字符串,如下所示。

    string displayName = nameList[n].LastName + ", " + nameList[n].FirstName;
  • 在循环里面append字符串的时候,特别是处理大文本的时候,使用StringBuilder对象。
    var phrase = "lalalalalalalalalalalalalalalalalalalalalalalalalalalalalala";
    var manyPhrases = new StringBuilder();
    for (var i = ; i < ; i++)
    {
    manyPhrases.Append(phrase);
    }
    //Console.WriteLine("tra" + manyPhrases); 吐槽:微软的这个示例并没有遵循他自己在本文中说的//要和注释文本之间留一个空白

本地变量使用隐示类型

  • 当变量的类型明显就是右边的表达式,或类型不是很重要的的时候使用 implicit typing

    // When the type of a variable is clear from the context, use var
    // in the declaration.
    var var1 = "This is clearly a string.";
    var var2 = ;
    var var3 = Convert.ToInt32(Console.ReadLine());
  • 当根据右边的表达式不是很容易能判断出其类型的时候,不使用var 。
    [Author("P. Ackerman", version = 1.1)]
    class SampleClass
  • 不要在变量名中包含变量的类型。
    Author anonymousAuthorObject = new Author("P. Ackerman");
    anonymousAuthorObject.version = 1.1;
  • 不要对 dynamic使用var。
  • for 和 foreach的循环参数中使用隐示类型。
    var syllable = "ha";
    var laugh = "";
    for (var i = ; i < ; i++)
    {
    laugh += syllable;
    Console.WriteLine(laugh);
    }
    foreach (var ch in laugh)
    {
    if (ch == 'h')
    Console.Write("H");
    else
    Console.Write(ch);
    }
    Console.WriteLine();

Unsigned数据类型

  • 通常不建议使用unsigned类型。

数组

  • 使用简单的语法声明初始化数组。

    // 推荐.
    string[] vowels1 = { "a", "e", "i", "o", "u" }; // If you use explicit instantiation, you can use var.
    var vowels2 = new string[] { "a", "e", "i", "o", "u" }; // If you specify an array size, you must initialize the elements one at a time.
    var vowels3 = new string[];
    vowels3[] = "a";
    vowels3[] = "e";
    // And so on.

Delegates

  • 使用简单的语法创建委托实例。

    // First, in class Program, define the delegate type and a method that
    // has a matching signature. // Define the type.
    public delegate void Del(string message); // Define a method that has a matching signature.
    public static void DelMethod(string str)
    {
    Console.WriteLine("DelMethod argument: {0}", str);
    }
    // In the Main method, create an instance of Del.
    
    // 推荐
    Del exampleDel2 = DelMethod; // The following declaration uses the full syntax.
    Del exampleDel1 = new Del(DelMethod);

try-catch and using Statements in Exception Handling

  • Use a try-catch statement for most exception handling.

    static string GetValueFromArray(string[] array, int index)
    {
    try
    {
    return array[index];
    }
    catch (System.IndexOutOfRangeException ex)
    {
    Console.WriteLine("Index is out of range: {0}", index);
    throw;
    }
    }
  • 使用using替代try finally。
    // This try-finally statement only calls Dispose in the finally block.
    Font font1 = new Font("Arial", 10.0f);
    try
    {
    byte charset = font1.GdiCharSet;
    }
    finally
    {
    if (font1 != null)
    {
    ((IDisposable)font1).Dispose();
    }
    } // You can do the same thing with a using statement.
    using (Font font2 = new Font("Arial", 10.0f))
    {
    byte charset = font2.GdiCharSet;
    }

      

&& and || Operators

  • 使用&& 替代& 、||、 | 这样可以避免不必要的比较从而提高性能。

    Console.Write("Enter a dividend: ");
    var dividend = Convert.ToInt32(Console.ReadLine()); Console.Write("Enter a divisor: ");
    var divisor = Convert.ToInt32(Console.ReadLine()); // If the divisor is 0, the second clause in the following condition
    // causes a run-time error. The && operator short circuits when the
    // first expression is false. That is, it does not evaluate the
    // second expression. The & operator evaluates both, and causes
    // a run-time error when divisor is 0.
    if ((divisor != 0) && (dividend / divisor > 0))
    {
    Console.WriteLine("Quotient: {0}", dividend / divisor);
    }
    else
    {
    Console.WriteLine("Attempted division by 0 ends up here.");
    }

      

New操作符

  • 实例化对象的时候使用隐示类型。

    var instance1 = new ExampleClass();

    上面的代码等于

    ExampleClass instance2 = new ExampleClass();
  • 使用对象初始化器来简单的创建对象。
    // 对象初始化器.
    var instance3 = new ExampleClass { Name = "Desktop", ID = ,
    Location = "Redmond", Age = 2.3 }; // Default constructor and assignment statements.
    var instance4 = new ExampleClass();
    instance4.Name = "Desktop";
    instance4.ID = ;
    instance4.Location = "Redmond";
    instance4.Age = 2.3;

事件处理

  • 如果你定义了一个不需要删除的事件处理器,使用lambda表达式。

    public Form2()
    {
    // You can use a lambda expression to define an event handler.
    this.Click += (s, e) =>
    {
    MessageBox.Show(
    ((MouseEventArgs)e).Location.ToString());
    };
    }

      

    // Using a lambda expression shortens the following traditional definition.
    public Form1()
    {
    this.Click += new EventHandler(Form1_Click);
    } void Form1_Click(object sender, EventArgs e)
    {
    MessageBox.Show(((MouseEventArgs)e).Location.ToString());
    }

静态成员

  • Call static members by using the class name: ClassName.StaticMember. This practice makes code more readable by making static access clear. Do not qualify a static member defined in a base class with the name of a derived class. While that code compiles, the code readability is misleading, and the code may break in the future if you add a static member with the same name to the derived class.

LINQ查询

  • 使用有意义的查询变量名。下面的实例使用seattleCustomers表示在Seattle的客户。

    var seattleCustomers = from cust in customers
    where cust.City == "Seattle"
    select cust.Name; 
  • 匿名类型的属性名使用Pascal casing。
    var localDistributors =
    from customer in customers
    join distributor in distributors on customer.City equals distributor.City
    select new { Customer = customer, Distributor = distributor };
  • 当结果中的属性名容易让人造成误解的时候,重命名这些属性名。例如,查询返回一个客户的名字和经销商的ID,我们不使用Name和ID做为属性名,而是使用CustomerName和DistributorID。
    var localDistributors2 =
    from cust in customers
    join dist in distributors on cust.City equals dist.City
    select new { CustomerName = cust.Name, DistributorID = dist.ID };
  • 使用隐示变量声明query。
    var seattleCustomers = from cust in customers
    where cust.City == "Seattle"
    select cust.Name;
  • 查询子句和from对齐。
  • Use where clauses before other query clauses to ensure that later query clauses operate on the reduced, filtered set of data.
    var seattleCustomers2 = from cust in customers
    where cust.City == "Seattle"
    orderby cust.Name
    select cust;
  • 使用多个from子句来代替join进入到内部关联。
    // Use a compound from to access the inner sequence within each element.
    var scoreQuery = from student in students
    from score in student.Scores
    where score >
    select new { Last = student.LastName, score };
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