Coding Guidelines

NOTE: This coding standard for MonoGame is a work in progress and much of the code does not currently conform to these rules. This is something that will be addressed by the team in the coming weeks.

Introduction

As the MonoGame project gains more traction and becomes more widely used, we are aiming to provide a more professional and consistent look to the large amount of source now in the project. It was a broadly supported decision by the core development team to follow the Microsoft coding guidelines (the default provided in Visual Studio's C# editor). These coding guidelines listed below have been based on a MSDN blog post from 2005 by Brad Abrams describing the internal coding guidelines at Microsoft, with some changes to suit our project.

Coding Guidelines

Tabs & Indenting

Tab characters (\0x09) should not be used in code. All indentation should be done with 4 space characters.

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. Single statements do not have braces. For example:

if (someExpression)
{
   DoSomething();
   DoAnotherThing();
}
else
   DoSomethingElse();

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

switch (someExpression) 
{
   case 0:
      DoSomething();
      break;

   case 1:
      DoSomethingElse();
      break;

   case 2: 
      {
         int n = 1;
         DoAnotherThing(n);
      }
      break;
}

Braces are not used for single statement blocks immediately following a for, foreach, if, do, etc. The single statement block should always be on the following line and indented by four spaces. This increases code readability and maintainability.

for (int i = 0; i < 100; ++i)
    DoSomething(i);

Single line property statements

Single line property statements can have braces that begin and end on the same line. This should only be used for simple property statements.

public class Foo
{
   int bar;

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

Commenting

Comments should be used to describe intention, algorithmic overview, and/or logical flow. 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.

Comments must provide added value or explanation to the code. Simply describing the code is not helpful or useful.

    // Wrong
    // Set count to 1
    count = 1;

    // Right
    // Set the initial reference count so it isn't cleaned up next frame
    count = 1;

Copyright/License 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. This is a short statement declaring the project name, copyright notice and directing the reader to the license document elsewhere in the project.

// MonoGame - Copyright (C) The MonoGame Team
// This file is subject to the terms and conditions defined in
// file 'LICENSE.txt', which is part of this source code package.

Documentation Comments

All methods should use XML doc comments. For internal dev comments, the 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)
    {
        …
    }
}

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();

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.

Console.In.Read(myChar, 0, 1);  // Right
Console.In.Read(myChar,0,1);    // Wrong

Do not use a space after the parenthesis and function arguments

CreateFoo(myChar, 0, 1)         // Right
CreateFoo( myChar, 0, 1 )       // Wrong

Do not use spaces between a function name and parenthesis.

CreateFoo()                     // Right
CreateFoo ()                    // Wrong

Do not use spaces inside brackets.

x = dataArray[index];           // Right
x = dataArray[ index ];         // Wrong

Do use a single space before flow control statements

while (x == y)                  // Right
while(x==y)                     // Wrong

Do use a single space before and after comparison operators

if (x == y)                     // Right
if (x==y)                       // Wrong

Naming

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

• Do not use Hungarian notation
• Do use an underscore prefix for member variables, e.g. _foo
• Do use camelCasing for member variables (first word all lowercase, subsequent words initial uppercase)
• Do use camelCasing for parameters
• Do use camelCasing for local variables
• Do use PascalCasing for function, property, event, and class names (all words initial uppercase)
• 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, underscore 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.

File Organization

• Source files should contain only one public type, although multiple internal classes are allowed if required
• Source files should be given the name of the public class in the file
• Directory names should follow the namespace for the class after Framework. For example, I would expect to find the public class Microsoft.Xna.Framework.Graphics.GraphicsDevice in MonoGame.Framework\Graphics\GraphicsDevice.cs
• Class members should be grouped logically, and encapsulated into regions (Fields, Constructors, Properties, Events, Methods, Private interface implementations, Nested types)
• Using statements should be before the namespace declaration.

using System;

namespace MyNamespace 
{
    public class MyClass : IFoo 
    {
        #region Fields
        int foo;
        #endregion

        #region Properties
        public int Foo { get { … } set { … } }
        #endregion

        #region Constructors
        public MyClass()
        {
            …
        }
        #endregion

        #region Events
        public event EventHandler FooChanged { add { … } remove { … } }
        #endregion

        #region Methods
        void DoSomething()
        {
            …
        }

        void FindSomething()
        {
            …
        }
        #endregion

        #region Private interface implementations
        void IFoo.DoSomething()
        {
            DoSomething();
        }
        #endregion

        #region Nested types
        class NestedType
        {
            …
        }
        #endregion
    }
}

Useful Links

C# Coding Conventions (MSDN)