Thursday, June 12, 2008

.NET Coding Guidelines

1. Tabs & Indenting

Avoid tab characters (\0x09) usage in code. 4 Space charactors should be use unsteade.

2 Bracing

Open braces should always be at the beginning of the line after the statement that begins the block. Contents of the brace should be indented by 4 spaces. For example:

if (someCondition)

"case" statements should be indented from the switch statement like this:

switch (someExpression)

case 0:

case 1:

case 2:
int n = 1;

Braces should never be considered optional. Even for single statement blocks, you should always use braces. This increases code readability and maintainability of your code.

3 Single line statements

Single line statements can have braces that begin and end on the same line.

public class Foo
int bar;

public int Bar
get { return bar; }
set { bar = value; }


It is suggested that all control structures (if, while, for, etc.) use braces, but it is not required.

4 Commenting

Comments should be used to describe intention, logical as well as execution flow, algorithmic overview. It would be ideal, if from reading the comments alone, someone other than the author could understand a function's intended behavior and general operation. While there are no minimum comment requirements and certainly some very small routines need no commenting at all, it is hoped that most routines will have comments reflecting the programmer's intent and approach.

Copyright notice

Each file should start with a copyright notice. To avoid errors in doc comment builds, you don't want to use triple-slash doc comments, but using XML makes the comments easy to replace in the future. Final text will vary by product (you should contact legal for the exact text), but should be similar to:

// <copyright file="ContainerControl.cs" company="Microsoft">
// Copyright (c) Microsoft Corporation. All rights reserved.
// </copyright>

Documentation Comments

All methods should use XML doc comments. For internal dev comments, the <devdoc> tag should be used.

public class Foo

/// <summary>Public stuff about the method</summary>
/// <param name="bar">What a neat parameter!</param>
/// <devdoc>Cool internal stuff!</devdoc>
public void MyMethod(int bar) { … }


However, it is common that you would want to move the XML documentation to an external file – for that, use the <include> tag.

public class Foo

/// <include file='doc\Foo.uex' path='docs/doc[@for="Foo.MyMethod"]/*' />
public void MyMethod(int bar) { … }


UNDONE§ there is a big doc with all the comment tags we should be using… where is that?

Comment Style

The // (two slashes) style of comment tags should be used in most situations. Where ever possible, place comments above the code instead of beside it. Here are some examples:

// This is required for WebClient to work through the proxy
GlobalProxySelection.Select = new WebProxy("http://itgproxy/");

// Create object to access Internet resources
WebClient myClient = new WebClient();

Comments can be placed at the end of a line when space allows:

public class SomethingUseful
private int itemHash; // instance member
private static bool hasDoneSomething; // static member

5 Spacing

Spaces improve readability by decreasing code density. Here are some guidelines for the use of space characters within code:

  • Do use a single space after a comma between function arguments.
    Right: Console.In.Read(myChar, 0, 1);
    Wrong: Console.In.Read(myChar,0,1);
  • Do not use a space after the parenthesis and function arguments
    Right: CreateFoo(myChar, 0, 1)
    Wrong: CreateFoo( myChar, 0, 1 )
  • Do not use spaces between a function name and parenthesis.
    Right: CreateFoo()
    Wrong: CreateFoo ()
  • Do not use spaces inside brackets.
    Right: x = dataArray[index];
    Wrong: x = dataArray[ index ];
  • Do use a single space before flow control statements
    Right: while (x == y)
    Wrong: while(x==y)
  • Do use a single space before and after comparison operators
    Right: if (x == y)
    Wrong: if (x==y)

6 Naming

Follow all .NET Framework Design Guidelines for both internal and external members. Highlights of these include:

  • Do not use Hungarian notation
  • Do not use a prefix for member variables (_, m_, s_, etc.). If you want to distinguish between local and member variables you should use "this." in C# and "Me." in VB.NET.
  • Do use camelCasing for member variables
  • Do use camelCasing for parameters
  • Do use camelCasing for local variables
  • Do use PascalCasing for function, property, event, and class names
  • Do prefix interfaces names with "I"
  • Do not prefix enums, classes, or delegates with any letter

The reasons to extend the public rules (no Hungarian, no prefix for member variables, etc.) is to produce a consistent source code appearance. In addition a goal is to have clean readable source. Code legibility should be a primary goal.

7 Naming Conventions

Interop Classes

Classes that are there for interop wrappers (DllImport statements) should follow the naming convention below:

  • NativeMethods – No suppress unmanaged code attribute, these are methods that can be used anywhere because a stack walk will be performed.
  • UnsafeNativeMethods – Has suppress unmanaged code attribute. These methods are potentially dangerous and any caller of these methods must do a full security review to ensure that the usage is safe and protected as no stack walk will be performed.
  • SafeNativeMethods – Has suppress unmanaged code attribute. These methods are safe and can be used fairly safely and the caller isn't needed to do full security reviews even though no stack walk will be performed.

class NativeMethods
private NativeMethods() {}

internal static extern void FormatHardDrive(string driveName);

class UnsafeNativeMethods
private UnsafeNativeMethods() {}

internal static extern void CreateFile(string fileName);

class SafeNativeMethods
private SafeNativeMethods() {}

internal static extern void MessageBox(string text);

All interop classes must be private, and all methods must be internal. In addition a private constructor should be provided to prevent instantiation.

8 File Organization

  • Source files should contain only one public type, although multiple internal classes are allowed
  • Source files should be given the name of the public class in the file
  • Directory names should follow the namespace for the class

For example, I would expect to find the public class "System.Windows.Forms.Control" in "System\Windows\Forms\Control.cs"…

  • Classes member should be alphabetized, and grouped into sections (Fields, Constructors, Properties, Events, Methods, Private interface implementations, Nested types)
  • Using statements should be inside the namespace declaration.

namespace MyNamespace

using System;

public class MyClass : IFoo

// fields
int foo;

// constructors
public MyClass() { … }

// properties
public int Foo { get { … } set { … } }

// events
public event EventHandler FooChanged { add { … } remove { … } }

// methods
void DoSomething() { … }
void FindSomethind() { … }

//private interface implementations
void IFoo.DoSomething() { DoSomething(); }

// nested types
class NestedType { … }