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C# coding standard

Important: Use CSharpGuidelines for any topics not covered in this document.

The coding standard is primarily based on CSharpGuidelines (by Aviva Solutions) but differs from it in these ways:

File Organization

1. Source file name and class name should always match.

MyClass.cs → public class MyClass { ... }

2. Directory names should follow namespace for the class.

System.Windows.Forms.Control should use the path System\Windows\Forms\Control.cs

Do not use namespace name with dots. This will make it easier to map namespaces to the directory layout.

Formatting

Layout

1. Avoid putting multiple namespaces or classes per file.

This will make your code more readable and also make it easier to find the .cs file for a particular class.

2. Place using directives at the top of the file, grouped and ordered alphabetically.

// .NET namespaces first
using System;
using System.Collections;

// Then any other namespaces in alphabetical order
using Company.Business;
using Company.Standard;

using Telerik.Ajax;
using Telerik.WebControls;

3. Maintain a common order for each file.

  1. Member variable
  2. Constructors and Finalizer
  3. Nested Enums, Structs and Classes
  4. Properties
  5. Methods

Sequence declaration within type groups are based on StyleCop's SA1202 ordering: public, internal, protected internal, protected, private.

Indentation

1. Basic indentation should be 4 spaces(not tabs).

// A Hello World! program in C#.
using System;

namespace HelloWorld
{
    class Hello 
    {
        static void Main() 
        {
            Console.WriteLine("Hello World!");
        }
    }
}

2. Maximum line length is 130 characters.

When an expression does not fit, follow the general guidelines:

  • Break after a comma
  • Break after an operator
  • Align the new line with the beginning of the expression at the same level on the previous line
  • Prefer higher-level breaks to lower-level breaks

Example of breaking up method calls:

Good
longMethodCall(expr1, expr2,
               expr3, expr4, expr5);
Bad  
longMethodCall(expr1, expr2
        ,expr3, expr4, expr5);

Example of breaking an arithmetic expression:

Good
var result = a * b / (c - g + f) +
             4 * z;
Bad  
var result = a * b / (c - g +
             f) + 4 * z;

The top one is preferred, since the break occurs outside the parenthesized expression, which is higher-level.

3. Always place curly braces on a new line.

This is known as the https://en.wikipedia.org/wiki/Indent_style#Allman_style[Allman style].

while (x < y)
{
    firstMethod();
    secondMethod();
}

lastMethod();

4. Always put curly braces even if it might not be required.

Such as having only one statement in the if clause. This is to enforce consistency.

if (x > y) 
{
    doSomething();
}

White Space

1. General guidelines.

  • Keywords like if, while should be followed by a white space.
  • Semicolons in for statements should be followed by a white space.
  • Commas should be followed by a white space.
  • Add a white space around operators like +, -, == etc.
  • Do not add white space after ( and before ).

Examples:

Good

a = (b + c) * d;
while (true)
doSomething(a, b, c, d)
for (i = 0; i < 10; i++)

Bad  

a=(b+c)*d;
while(true)
doSomething(a,b,c,d)
for(i=0;i<10;i++)

Naming

1. All names should be written in English.

English is the preferred language for international development.

2. Use proper casing for language elements.

  • Pascal casing: the first letter of every word is capitalized.
  • Camel casing: the first letter of every word, except for the first word, is capitalized.
Language element Casing Example
Class, Struct Pascal AppDomain
Interface Pascal IBusinessService
Enumeration type Pascal ErrorLevel
Enumeration values Pascal FatalError
Event Pascal Click
Private field Camel listItem
Protected field Pascal MainPanel
Constant field Pascal MaximumItems
Constant local variable Camel maximumItems
Read-only static field Pascal RedValue
Local variable Camel listOfValues
Method Pascal ToString
Namespace Pascal System.Drawing
Parameter Camel typeName
Type parameter Pascal TView
Property Pascal BackColor

3. Avoid using abbreviations.

Unless the full name is excessive:

  • Avoid abbreviations longer than 5 characters.
  • Abbreviations must be widely known and accepted.
  • Use upper case for 2-character abbreviations, and Pascal Case for longer abbreviations.
Good
UIControl
HtmlSource
Bad  
UiControl
HTMLSource

4. Prefix boolean variables with Can, Is, or Has.

Examples: CanEvaluate, IsVisible, HasLicense.

Avoid boolean variables that represent the negation of things. e.g., use IsInitialized instead of IsNotInitialized.

5. Do not include the parent class name within a property name.

Good
Customer.Name
Bad  
Customer.CustomerName

6. Do not use Hungarian Notation.

Hungarian notation is a defined set of pre and postfixes which are applied to names to reflect the type of the variable. This style was used in early Windows programming, but is now obsolete.

Good
Name
Colors
Bad  
strName
ColorsEnum

Exception: All fields and variable names that contain GUI elements like button should be postfixed with their type name without abbreviations. e.g., cancelButton, nameTextBox.

Commenting

1. General guidelines.

  • Place the comment on a separate line, not at the end of a line of code.
  • Begin comment text with an upper case letter.
  • Insert one space between comment delimiter (//) and comment text.
  • Use // or /// but never /* ... */.
  • The length of comment should not exceed the length of code.

2. Document all public, protected and internal types and members.

Documenting your code allows Visual Studio to pop-up the documentation when your class is used somewhere else. You can form your documentation using https://msdn.microsoft.com/en-us/library/5ast78ax.aspx[XML tags].

/// <summary>
/// Get a value indicating whether the user has a license.
/// </summary>
/// <returns>
/// <c>true</c> if the user has a license; otherwise <c>false</c>.
/// </returns>
public bool HasLicense() { ... }

Language Conventions

1. Do not omit access modifiers.

Explicitly declare all identifiers with the appropriate access modifiers instead of allowing the default.

Good
private void WriteEvent(string message)
Bad  
void WriteEvent(string message)

2. Always use the built-in C# data type aliases, instead of the .NET common type system.

Good
short
int
long
string
Bad  
Int16
Int32
Int64
String

3. Only use var when the type is very obvious.

When the type of a variable is clear from the context, use var in the declaration.

var welcomeMessage = "This is a welcome message!";
var account = new Account();

Do not use var when the type is not apparent from the right side of the assignment.

int result = ExampleClass.ResultSoFar();

To know more about when to use/not to use implicit typing read Uses and misuses of implicit typing.

4. Favor Object and Collection initializers over separate statements.

Good
var startInfo = new ProcessStartInfo("myapp.exe");
{
    StandardOutput = Console.Output,
    UseShellExecute = true
};
Bad  
var startInfo = new ProcessStartInfo("myapp.exe");
startInfo.StandardOutput = Console.Output;
startInfo.UseShellExecute = true;

References