Coding Standards Guidelines for MS Professionals

This document describes rules and recommendations for developing applications and class libraries using the C# Language. The goal is to define guidelines to enforce consistent style and formatting and help developers avoid common pitfalls and mistakes.

Specifically, this document covers Naming Conventions, Coding Style, Language Usage, and Object ModelDesign.

Scope

This document only applies to the C# Language and the .NET Framework Common Type System(CTS) itimplements. Although the C# language is implemented alongside the .NET Framework, this document does notaddress usage of .NET Framework class libraries. However, common patterns and problems related to C#’s usage of the .NET Framework are addressed in a limited fashion.

Even though standards for curly-braces ({ or }) and white space(tabs vs. spaces) are always controversial, these topics are addressed here to ensure greater consistency and maintainability of source code.

Document Conventions

Much like the ensuing coding standards, this document requires standards in order to ensure clarity when stating the rules and guidelines. Certain conventions are used throughout this document to add emphasis.

Below are some of the common conventions used throughout this document.

Coloring & Emphasis

Blue Text colored blue indicates a C# keyword or .NET type.
Bold Text with additional emphasis to make it stand-out.

Keywords

Always Emphasizes this rule must be enforced.
Never Emphasizes this action must not happen.
Do Not Emphasizes this action must not happen.
Avoid Emphasizes that the action should be prevented, but some exceptions may exist.
Try Emphasizes that the rule should be attempted whenever possible and appropriate.
Example Precedes text used to illustrate a rule or recommendation.
Reason Explains the thoughts and purpose behind a rule or recommendation.

Terminology & Definitions

The following terminology is referenced throughout this document

Access Modifier

C# keywords public, protected, internal, and private declare the allowed code-accessibility of types and their members. Although default access modifiers vary, classes and mostother members use the default of private. Notable exceptions are interfaces and enums whichboth default to public

Camel Case

A word with the first letter lowercase, and the first letter of each subsequent word-part capitalized.Example:customerName

Common Type System

The .NET Framework common type system (CTS) defines how types are declared, used, andmanaged. All native C# types are based upon the CTS to ensure support for cross-language integration.

Identifier

A developer defined token used to uniquely name a declared object or object instance.Example: public class MyClassNameIdentifier{ … }

Magic Number

Any numeric literal used within an expression (or to initialize a variable) that does not have anobvious or well-known meaning. This usually excludes the integers 0 or 1 and any other numeric equivalent precision that evaluates as zero.

Pascal Case

A word with the first letter capitalized, and the first letter of each subsequent word-part capitalized. Example: CustomerName

Premature Generalization

As it applies to object model design; this is the act of creating abstractions within an object modelnot based upon concrete requirements or a known future need for the abstraction. In simplest terms: “Abstraction for the sake of Abstraction”.

Quick Summary

This section contains tables describing a high-level summary of the major standards covered in this document.These tables are not comprehensive, but give a quick glance at commonly referenced elements.

Naming Conventions

“c” camelCase
“P” PascalCase
“_” Prefix with _Underscore
“x” Not Applicable

Identifier Public Protected Internal Private Notes
Project File P x x x Match Assembly & Namespace
Source File P x x x Match contained class
Other Files P x x x Apply where possible
Namespace P x x x Partial Project/Assembly match
Class P P P P Add suffix of subclass
Struct P P P P Add suffix of subclass
Interface P P P P Prefix with a capital I
GenericClass P P P P Use T or K as Type identifier
Method P P P P Use a Verb or Verb-Object pair
Property P P P P Do not prefix with Get or Set
Field P P P _c Only use Private fields
No Hungarian Notation
Constant P P P _c
Static Field P P P _c Only use Private fields
Enum P P P P Options are also PascalCase
Delegate P P P P
Event P P P P
Inline Variable x x x c Avoid single-character and enumeratednames
Parameter x x x c

Coding Style

Code Style
Source Files One Namespace per file and one class per file.
Curly Braces On new line. Always use braces when optional.
Indention Use tabs with size of 4.
Comments Use // or /// but not /* … */ and do not flowerbox.
Variables One variable per declaration.

Language Usage

Code Style
Native Data Types Use built-in C# native data types vs .NET CTS types.
(Use int NOT Int32)
Enums Avoid changing default type.
Generics Prefer Generic Types over standard or strong-typed
Classes.
Properties Never prefix with Get or Set.
Methods Use a maximum of 7 parameters.
base and this Use only in constructors or within an override.
Ternary conditions Avoid complex conditions.
foreach statements Do not modify enumerated items within a foreach statement.
Conditionals Avoid evaluating Boolean conditions against true or false. No embedded assignment. Avoid embedded method invocation.
Exceptions Do not use exceptions for flow control.
Use throw; not throw e, when re-throwing.
Only catch what you can handle.
Use validation to avoid exceptions.
Derive from Execption not ApplicationException.
Events Always check for null before invoking.
Locking Use lock() not Monitor.Enter().
Do not lock on an object type or “this”.
Do lock on private objects.
Dispose() & Close() Always invoke them if offered, declare where needed.
Finalizers Avoid.Use the C# Destructors.
Do not create Finalize() method.
AssemblyVersion Increment manually.
ComVisibleAttribute Set to false for all assemblies.

Naming Conventions

Consistency is the key to maintainable code. This statement is most true for naming your projects, source files and identifiers including Fields, Variables, Properties, Methods, Parameters, Classes, Interfaces, and Namespaces.

General Guidelines

1. Always use Camel Case or Pascal Case names.
2. Avoid ALL CAPS and all lowercase names. Single lowercase words or letters are acceptable.
3. Do not create namespaces, classes, methods, properties, fields, or parameters that vary only by capitalization.
4. Do not use names that begin with a numeric character.
5. Always choose meaningful and specific names.
6. Always err on the side of verbosity not terseness.
7. Variables and Properties should describe an entity not the type or size.
8. Do not use Hungarian Notation Example: strName or iCount
9. Avoid using abbreviations unless the full name is excessive.
10. Avoid abbreviations longer than 5 characters.
11. Any Abbreviations must be widely known and accepted.
12. Use uppercase for two-letter abbreviations, and Pascal Case for longer abbreviations.
13. Do not use C# reserved words as names.
14. Avoid naming conflicts with existing .NET Framework namespaces, or types.
15. Avoid adding redundant or meaningless prefixes and suffixes to identifiers Example:
// Bad

public enum ColorsEnum {…}
public class CVehicle {…}
public struct Rectangle Struct{…}

16. Do not include the parent class name within a property name.
Example: Customer.Name NOT Customer.CustomerName
17. Try to prefix Boolean variables and properties with “Can”, “Is” or “Has”.
18. Append computational qualifiers to variable names like Average, Count, Sum, Min, and Max whereappropriate.
19. When defining a root namespace, use a Product, Company, or Developer Name as the root.

Example: LanceHunt.StringUtilities.

Name Usage & Syntax

Identifier Naming Convention
Project File Pascal Case.
Always match Assembly Name & Root Namespace.
Example:
LanceHunt.Web.csproj->LanceHunt.Web.dll->namespace
LanceHunt.Web
Source File Pascal Case.
Always match Class name and file name.

Avoid including more than one Class, Enum (global), or Delegate (global) per file. Use adescriptive file name when containing multiple Class, Enum, or Delegates

Example:MyClass.cs -> public class MyClass {…}
Resource Try to use Pascal Case.
Or
Embedded File Use a name describing the file contents.
Namespace Pascal Case.
Try to partially match Project/Assembly Name.

Example:namespace LanceHunt.Web{…}
Class or Struct Pascal Case.
Use a noun or noun phrase for class name.
Add an appropriate class-suffix when sub-classing another type
when possible.

Examples:
private class MyClass{…}
internal class SpecializedAttribute : Attribute{…}
public class CustomerCollection : CollectionBase{…}
public class CustomEventArgs : EventArgs{…}
private struct ApplicationSettings{…}

Interface Pascal Case.
Always prefix interface name with capital “I”.

Example:interface ICustomer{…}
Generic Class Always use a single capital letter, such as T or K.
&
Generic

Example:

ParameterType public class FifoStack
{
public void Push( obj)
{…}
public Pop()
{…}
}

Method Pascal Case.
Try to use a Verb or Verb-Object pair.

Example:

public void Execute()
{…}
private string GetAssemblyVersion(Assembly target)
{…}

Property Pascal Case.
Property name should represent the entity it returns. Never prefix property names with“Get” or “Set”.

Example:public string Name
{
get{…}
set{…}
}

Field Pascal Case.
(Public, Avoid using non-private Fields
Protected, Use Properties instead.
or Internal) Example:public string Name;protected IList InnerList;

Field (Private) Camel Case and prefix with a single underscore (_) character.
Example:private string _name;

Constant or Treat like a Field.
Static Field Choose appropriate Field access-modifier above.

Enum Pascal Case (both the Type and the Options).
Add the FlagsAttribute to bit-mask multiple options.

Example:public enum CustomerTypes
{
Consumer,
Commercial
}

Delegate or Event Treat as a Field.
Choose appropriate Field access-modifier above.

Example:public event EventHandler LoadPlugin;

Variable (inline) Camel Case.
Avoid using single characters like “x” or “y” except in FOR loops.
Avoid enumerating variable names like text1, text2, text3 etc.

Parameter Camel Case.

Example:

public void Execute(string commandText, int iterations){…}

Coding Style

Coding style causes the most inconsistency and controversy between developers. Each developer has a preference, and rarely are two the same. However, consistent layout, format, and organization are key tocreating maintainable code. The following sections describe the preferred way to implement C# source code inorder to create readable, clear, and consistent code that is easy to understand and maintain.

Formatting

1. Never declare more than 1 namespace per file.
2. Avoid putting multiple classes in a single file.
3. Always place curly braces ({ and }) on a new line.
4. Always use curly braces ({ and }) in conditional statements.
5. Always use a Tab & Indention size of 4.
6. Declare each variable independently – not in the same statement.
7. Place namespace “using” statements together at the top of file. Group .NET namespaces abovecustom namespaces.
8. Group internal class implementation by type in the following order:a. Member variables.b. Constructors & Finalizers.c. Nested Enums, Structs, and Classes.d. Propertiese. Methods
9. Sequence declarations within type groups based upon access modifier and visibility:a. Publicb. Protectedc. Internald. Private
10. Segregate interface Implementation by using #region statements.
11. Append folder-name to namespace for source files within sub-folders.
12. Recursively indent all code blocks contained within braces.
13. Use white space (CR/LF, Tabs, etc) liberally to separate and organize code.
14. Avoid declaring multiple attribute declarations within a single line. Instead stack each attributeas a separate declaration.

Example:

// Bad
[Attrbute1, Attrbute2, Attrbute3]
public class MyClass{…}
// Good
[Attrbute1]
[Attrbute2]
[Attrbute3]
public class MyClass{…}
15. Place Assembly scope attribute declarations on a separate line.
16. Place Type scope attribute declarations on a separate line.
17. Place Method scope attribute declarations on a separate line.
18. Place Member scope attribute declarations on a separate line.
19. Place Parameter attribute declarations inline with the parameter.
20. If in doubt, always err on the side of clarity and consistency.

Code Commenting

21. All comments should be written in U.S. English.
22. Use // or /// but never /* … */
23. Do not “flowerbox” comment blocks.

Example:
// ***************************************
// Comment block
// ***************************************

24. Use inline-comments to explain assumptions, known issues, and algorithm insights.
25. Do not use inline-comments to explain obvious code. Well written code is self documenting.
26. Only insert inline-comments for Bad Code to say “fix this code” – otherwise, rewrite it
27. Include Task-List keyword flags to enable comment-filtering.

Example:
// TODO: Place Database Code Here
// UNDONE: Removed P\Invoke Call due to errors
// HACK: Temporary fix until able to refactor

28. Always apply C# comment-blocks (///) to public, protected, and internal declarations.
29. Only use C# comment-blocks for documenting the API.
30. Always include

comments. Include , , and comment sections where applicable.
31. Include and where possible.
32. Always add CDATA tags to comments containing code and other embedded markup in order toavoid encoding issues.

Example:
///
/// Add the following key to the “appSettings” section of your config:
///<![CDATA
///
///
///
///
///
/// ]>

///

Language Usage

General

1. Do not omit access modifiers. Explicitly declare all identifiers with the appropriate access modifierinstead of allowing the default.

Example:

// Bad
Void WriteEvent(string message){…}
// Good
private Void WriteEvent(string message){…}

2. Do not use the default (“1.0.*”) versioning scheme. Increment the AssemblyVersionAttributevalue manually.
3. Set the ComVisibleAttribute to false for all assemblies. Afterwards, selectively enable theComVisibleAttribute for individual classes as needed.Example:[assembly: ComVisible(false)][ComVisible(true)]public MyClass{…}
4. Consider factoring classes with unsafe code blocks into a separate assembly.
5. Avoid mutual references between assemblies.

Variables & Types

1. Try to initialize variables where you declare them.
2. Use the simplest data type, list, or object required. For example, use int over. Long unless youknow you need to store 64bit values.
3. Always use the built-in C# data type aliases, not the .NET common type system (CTS).

Example:

short NOT System.Int16
int NOT System.Int32
long NOT System.Int64
string NOT System.String

4. Only declare member variables as private. Use properties to provide access to them withpublic, protected, or internal access modifiers.
5. Avoid specifying a type for an enum – use default of int unless you have an explicit need for long.
6. Avoid using inline numeric literals (magic numbers). Instead, use a Constant or Enum.
7. Avoid declaring inline string literals. Instead use Constants, Resources, Registry or other datasources.
8. Only declare constants for simple types.
9. Declare readonly or static readonly variables instead of constants for complex types.
10. Avoid direct casts. Instead, use the “as” operator and check for null.Example:object dataObject = LoadData();DataSet ds = dataObject as DataSet;if(ds != null){…}
11. Always prefer C# Generic collection types over standard or strong-typed collections.
12. Always explicitly initialize arrays of reference types using a for loop.
13. Avoid boxing and unboxing value types.Example:int count = 1;object refCount = count;// Implicitly boxed.int newCount = (int)refCount; // Explicitly unboxed.
14. Floating point values should include at least one digit before the decimal place and one after.Example: totalPercent = 0.05;
15. Try to use the “@” prefix for string literals instead of escaped strings.
16. Prefer String.Format() or StringBuilder over string concatenation.
17. Never concatenate strings inside a loop.
18. Do not compare strings to String.Empty or “” to check for empty strings. Instead, compare byusing String.Length == 0.
19. Avoid hidden string allocations within a loop. Use String.Compare() instead.

Example:

(ToLower() creates a temp string)
// Bad
int id = -1;
string name = “lance hunt”;
for(int i=0; i < customerList.Count; i++)
{
if(customerList[i].Name.ToLower() == name)
{id = customerList[i].ID;}
}
// Good
int id = -1;
string name = “lance hunt”;
for(int i=0; i < customerList.Count; i++)
{
// The “ignoreCase = true” argument performs a
// case-insensitive compare without new allocation.
if(String.CompareString.Compare(customerList[i].Name, name, true)== 0)
{id = customerList[i].ID;}}

Flow Control

1. Avoid invoking methods within a conditional expression.
2. Avoid creating recursive methods. Use loops or nested loops instead.
3. Avoid using foreach to iterate over immutable value-type collections. E.g. String arrays.
4. Do not modify enumerated items within a foreach statement.
5. Use the ternary conditional operator only for trivial conditions. Avoid complex or compound ternaryoperations.
Example: int result = isValid ? 9 : 4;
6. Avoid evaluating Boolean conditions against true or false.
Example:// Bad!if (isValid == true){…}// Good!if (isValid){…}
7. Avoid assignment within conditional statements.
Example: if((i=2i=2i=2i=2)==2) {…}
8. Avoid compound conditional expressions – use Boolean variables to split parts into multiplemanageable expressions.

Example:

// Bad
if (((value > _highScore) && (value != _highScore)) && (value = _highScore);isTiedHigh = (value == _highScore);isValid = (value < _maxValue);
if ((isHighScore && ! isTiedHigh) && isValid)
{…}
9. Avoid explicit Boolean tests in conditionals.
Example:// Bad!if(IsValid == true){…};// Good!if(IsValid){…}
10. Only use switch/case statements for simple operations with parallel conditional logic.
11. Prefer nested if/else over switch/case for short conditional sequences and complexconditions.
12. Prefer polymorphism over switch/case to encapsulate and delegate complex operations.

Exception Handling

1. Do not use try/catch blocks for flow-control.
2. Only catch exceptions that you can handle.
3. Never declare an empty catch block.
4. Avoid nesting a try/catch within a catch block.
5. Use exception filters where possible.
6. Order exception filters from most to least derived exception type.
7. Avoid re-throwing an exception. Allow it to bubble-up instead.
8. If re-throwing an exception, omit the exception argument from the throw statement so the originalcall stack is preserved.

Example:

// Bad
catch(Exception ex)
{
Log(ex);
throw ex;
}
// Good
catch(Exception ex)
{
Log(ex);
throw;
}
9. Only use the finally block to release resources from a try statement.
10. Always use validation to avoid exceptions.
Example:
// Bad
try
{
conn.Close();
}
Catch(Exception ex)
{
// handle exception if already closed!
}
// Good
if(conn.State != ConnectionState.Closed)
{
conn.Close();
}
11. Avoid defining custom exception classes. Use existing exception classes instead.
12. When a custom exception is required –
a. Always derive from Exception not ApplicationException.
b. Always override the ToString() method and String implicit operator to provideserialization.
c. Always implement the Exception Constructor Pattern:
public MyCustomException ();
public MyCustomException (string message);
public MyCustomException (string message, Exception innerException);
13. When throwing a new Exception, always pass the innerException in order to maintain theexception tree & inner call stack.

Events, Delegates, & Threading

1. Always check Event & Delegate instances for null before invoking.
2. Use the default EventHandler and EventArgs for most simple events.
3. Always derive a custom EventArgs class to provide additional data.
4. Use the existing CancelEventArgs class to allow the event subscriber to control events.
5. Always use the “lock” keyword instead of the Monitor type.
6. Only lock on a private or private static object.
Example: lock(myVariable);
7. Avoid locking on a Type.
Example: lock(typeof(MyClass));
8. Avoid locking on the current object instance.
Example: lock(this);

Object Composition

1. Always declare types explicitly within a namespace. Do not use the default “{global}” namespace.
2. Avoid declaring methods with more than 7 parameters. Refactor or consider passing a struct orclass instead.
3. Do not use the “new” keyword to hide members of a derived type.
4. Only use the “base” keyword when invoking a base class constructor or base implementation withinan override.
5. Do not use the protected access modifier in sealed classes.
6. Consider using method overloading instead of the params attribute.
7. Always validate an enumeration variable or parameter value before consuming it. They may containany value that the underlying Enum type (default int) supports.

Example:

public void Test(BookCategory cat)
{
if (Enum.IsDefined(typeof(BookCategory), cat))
{…}
}

8. Consider overriding Equals() on a struct.
9. Always override the Equality Operator (==) when overriding the Equals() method.
10. Always override the String Implicit Operator when overriding the ToString() method.
11. Always call Close() or Dispose() on classes that offer it.
12. Wrap instantiation of IDisposable objects with a “using” statement to ensure that Dispose() isautomatically called.

Example:

using(SqlConnection cn = new SqlConnection(_connectionString)){…}
13. Always implement the IDisposable interface & pattern on classes referencing external resources.

Example:

(shown with optional Finalizer)
public void Dispose()
{
Dispose(true);
GC.SuppressFinalize(this);
}
protected virtual void Dispose(bool disposing)
{
if (disposing)
{
// Free other state (managed objects).
}
// Free your own state (unmanaged objects).
// Set large fields to null.
}
// C# finalizer.
(optional)Base()
{
// Simply call Dispose(false).
Dispose (false);
}
14. Avoid implementing a Finalizer.Never define a Finalize() method as a finalizer. Instead use the C# destructor syntax.

Example:

// Good
MyClass
{…}
// Bad
void Finalize()
{…}

Object Model Design

1. Always prefer delegation over inheritance.
2. Avoid “Premature Generalization”. Create abstractions only when the intent is understood.
3. Do the simplest thing that works, then refactor as time permits.
4. Always make object-behavior transparent to API consumers.
5. Always separate presentation layer from business logic.
6. Always prefer interfaces over abstract classes.
7. Try to append the design-pattern name to class names where appropriate.
8. Make members virtual if they are designed and tested for extensibility.
9. Consider using the “sealed” keyword to break the inheritance chain.