C# 程式碼風格指南

原文：C# Coding Conventions (C# Programming Guide)

Naming Conventions

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();

Layout Conventions

• four-character indents, tabs saved as spaces
• Write only one statement per line.
• Write only one declaration per line.
• If continuation lines are not indented automatically, indent them one tab stop (four spaces).
• Add at least one blank line between method definitions and property definitions.
• Use parentheses to make clauses in an expression apparent, as shown in the following code.
  • if ((val1 > val2) && (val1 > val3))

Commenting Conventions

• Place the comment on a separate line, not at the end of a line of code.
• Begin comment text with an uppercase letter.
• End comment text with a period.
• Insert one space between the comment delimiter // and the comment text

  // The following declaration creates a query. It does not run
  // the query.

• Do not create formatted blocks of asterisks around comments.

Language Guidelines

• Use string interpolation to concatenate short strings, as shown in the following code.
  • string displayName = $"{nameList[n].LastName}, {nameList[n].FirstName}";
• To append strings in loops, especially when you are working with large amounts of text, use a StringBuilder object.

  var phrase = "la";
  var manyPhrases = new StringBuilder();
  for (var i = 0; i < 10000; i++)
  {
      manyPhrases.Append(phrase);
  }
  //Console.WriteLine("tra" + manyPhrases);

Implicitly Typed Local Variables

• Use implicit typing for local variables when the type of the variable is obvious from the right side of the assignment, or when the precise type is not important.

  var var1 = "This is clearly a string.";
  var var2 = 27;

• Do not use var when the type is not apparent from the right side of the assignment.
  • A variable type is considered clear if it’s a new operator or an explicit cast.

    int var3 = Convert.ToInt32(Console.ReadLine());
    int var4 = ExampleClass.ResultSoFar();

• Use implicit typing to determine the type of the loop variable in for loops.
• Do not use implicit typing to determine the type of the loop variable in foreach loops.

Arrays

Use the concise syntax when you initialize arrays on the declaration line.

// Preferred syntax. Note that you cannot use var here instead of string[].
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[5];
vowels3[0] = "a";
vowels3[1] = "e";

Delegates

// 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.
// Preferred: Create an instance of Del by using condensed syntax.
Del exampleDel2 = DelMethod;
// The following declaration uses the full syntax.
Del exampleDel1 = new Del(DelMethod);

Simplify your code by using the C# using statement

// Method1: try-finally statement with Dispose
Font font1 = new Font("Arial", 10.0f);
try
{
    byte charset = font1.GdiCharSet;
}
finally
{
    if (font1 != null)
    {
        ((IDisposable)font1).Dispose();
    }
}

// Method2: Using statement.
using (Font font2 = new Font("Arial", 10.0f))
{
    byte charset = font2.GdiCharSet;
}

&& and || Operators

• To avoid exceptions and increase performance by skipping unnecessary comparisons, use && instead of & and || instead of | when you perform comparisons
  • The && operator short circuits when the first expression is false
  • 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 Operator

• Use var in when using new: var instance1 = new ExampleClass();
• Use object initializers to simplify object creation.
  • var instance3 = new ExampleClass { Name = "Desktop", ID = 37414, Location = "Redmond", Age = 2.3 };

Event Handling

• If you are defining an event handler that you do not need to remove later, use a lambda expression.

  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());
  }

Static Members

• 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.

LINQ Queries

• Use meaningful names for query variables.

  var seattleCustomers = from customer in customers
                         where customer.City == "Seattle"
                         select customer.Name;

• Use aliases to make sure that property names of anonymous types using Pascal casing.

  var localDistributors =
      from customer in customers
      join distributor in distributors on customer.City equals distributor.City
      select new { Customer = customer, Distributor = distributor };

• Use implicit typing in the declaration of query variables and range variables.
• Align query clauses under the from clause, as shown in the previous examples.
• Use multiple from clauses instead of a join clause to access inner collections.

  // 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 > 90
                   select new { Last = student.LastName, score };