C# .NET Coding Conventions

We are a dedicated team of professionals with strong will to follow the best practices when we code.

As a team, we have to manage several documents with all the coding conventions, design patterns and principles we have to follow while writing our code.

While doing reviews, we are targeting pages from the conventions, so the team stays focused on the rules.

The team updates the documentation or introduces new rules only after a detailed investigation.

We have decided to make the documentation public in order to help others who will want to implement the same.

Today, we are making public our internal “Coding Tutorial” document.

Credits

This C# style recommends best practices so that developers can write code maintainable by other C# developers.
The document contains data collected from various sources, language styles, and communities.

• docs.microsoft.com
• dofactory.com
• github.com/ktaranov
• c-sharpcorner.com
• stylecop.soyuz5.com
• google.github.io

Table of contents

• General
  • Naming
  • Brackets
• Structure and layout
  • Namespaces
  • Interfaces
  • Classes
  • Modifiers
  • Documentation
  • Regions
  • Comments
• Spacing and readability
  • Tabs and line break
  • Curly brackets
  • Square brackets
  • Parenthesis
  • Symbols
  • Signs
  • Layout
  • Parameters
  • Misc
• Types and variables
• Expressions
• Statements
• Queries and Linq

General

Naming

• ✔ Use PascalCase, camelCase and SNAKE_CASE

Object Name	Notation	Length	Char Mask
Class name	PascalCase	128	[A-z][0-9]
Constructor name	PascalCase	128	[A-z][0-9]
Method name	PascalCase	128	[A-z][0-9]
Method arguments	camelCase	128	[A-z][0-9]
Local variables	camelCase	50	[A-z][0-9]
Constants name	SNAKE_CASE	50	[A-z][0-9]
Field name	camelCase	50	[A-z][0-9]
Properties name	PascalCase	50	[A-z][0-9]
Delegate name	PascalCase	128	[A-z]
Enum type name	PascalCase	128	[A-z]

• ✔ Use PascalCasing to name classes, methods, and properties

class ClassName

void MethodName();

string PropertyName { get; set; }

• ✔ Use camelCasing to name method arguments, local variables, and fields

string fieldName;

void Method(int argumentOne, int argumentTwo);

Method(argumentOne, argumentTwo);

int localName = 10;

• ✔ Use SNAKE_CASE to name constants

const string SOME_CONSTANT = "constant value";

Brackets

• ✔ Vertically align curly brackets
  • Allman style. Wikipedia

namespace Application
{
    class Program
    {
        static void Main(string[] args)
        {
            if (...)
            {
            }
            else
            {
            }
                  
            while (...)
            {
            }
        }
    }
}

• ✖ Do not omit curly brackets
  • Always wrap the body of the statement in curly brackets.
  • Although this is legal in C#, the curly brackets are required to be present. They increase the readability and maintainability of the code.

✔

if (true)
{
    return this.x;
}

if (true)
{
    this.x = 42;

    return this.x;
}

✖

if (true) return this.x;

if (true)
    return this.x;

if (true)
    this.x = 42;

    return this.x;

• ✖ Do not place curly brackets on the same line with statements
  • Ensure that both opening and closing curly brackets are placed on their own (vertical) line.
  • Curly brackets should not share their line with any other code, other than comments.

✔

object Method()
{
    lock (...)
    {
        return this.x;
    }
}

✖

object Method() {
    lock (...) {
        return this.x;
    }
}

object Method()
{
    lock (...) { return this.x; }
}

Structure and layout

Namespaces

• ✔ Organize namespaces with a clearly defined structure
  • Use PascalCasing to name namespaces.

namespace Company.Product.Module.SubModule
namespace Product.Module.Component
namespace Product.Layer.Module.Group

• ✖ Do not place multiple namespaces within a single file
  • Ensure that each file contains only one namespace.
  • To increase long-term maintainability of the code-base, each file should contain at most one namespace.

// A.cs
namespace Project
{
    class A
    {
    }
}
      
// B.cs
namespace Project
{
    class B
    {
    }
}

• ✔ Separate non-static from static usings
  • Order usings alphabetically. Order by non-static, then by static.
  • Do not separate usings, or static/non-static blocks by blank line(s).

✔

using System;
using System.Linq;
using static System.Linq.Enumerable;
using static System.Math;

✖

using System;
using System.Linq;
      
using static System.Linq.Enumerable;
using static System.Math;

using System;
using static System.Math;
using System.Linq;
using static System.Linq.Enumerable;

• ✖ Do not line-wrap using statements
  • Always write using statements on a single line.

✔

using System.Security.Cryptography;

✖

using System
    .Security.Cryptography;

Interfaces

• ✔ Prefix interface names with letter I
  • Interface names are noun or adjectives.

✔

interface ILogger

interface IApplicationBuilder

interface ICollection

✖

interface LoggerSignature

interface LoggerInterface

interface LoggerIFace

• ✖ Do not (habitually) add new signatures at the end of the interface

✔

interface ITransfer
{
    void Connect();
    void Download();
    void Upload(); // Recently added signature
    void Notify();
    void Stop();
}

✖

interface ITransfer
{
    // ...
    void Stop();
    void Upload(); // Recently added signature
}

Classes

• ✔ Write each class in its own file
  • Use the same notation for file and class name.
  • Avoid nested classes.

✔

// Application.cs
class Application
{
}
      
// Program.cs
class Program
{
}

✖

// Application.cs
class ApplicationManager
{
    class Program
    {
    }
}

• ✔ Use PascalCasing when abbreviating three or more characters
  • When there are two characters, both are uppercase.

✔

HtmlHelper htmlHelper;
XmlDocument xmlDocument;
IOException ioException;
UIElement uiElement;

✖

HTMLHelper htmlHelper;
XMLDocument xmlDocument;
IoException ioException;
UiElement uiElement;

• ✔ Write both accessors single-line or multi-line. Do not mix styles.
  • Write both accessors single-line when the accessors are short.
  • Expand both accessors multi-lines when the accessors are long.

✔

bool IsEnabled { get; set; }

bool IsEnabled
{
    get => this.enabled;
    set => this.enabled = value;
}

bool IsEnabled
{
    get { return this.enabled; }
    set { this.enabled = value; }
}

bool IsEnabled
{
    get
    {
        return this.enabled;
    }
          
    set
    {
        this.enabled = value;
    }
}

✖

bool IsEnabled
{
    get;
    set;
}

bool IsEnabled
{
    get { return this.enabled; }
    set => this.enabled = value;
}

• ✔ Prefix local calls with this
  • Insert the this prefix before a call to a class member.

✔

class B : A
{
    private int x;
    private int y;
          
    public B(int x, int y, int z)
    {
        base.z = z;
        this.x = x;
        this.y = y;
    }
}

✖

class B : A
{
    private int m_x;
    private int _y;
          
    public B(int x, int y, int z)
    {
        base.z = z;
        m_x = x;
        _y = y;
    }
}

• ✖ Do not prefix calls with base unless local implementation exists
  • A call to a member from an inherited class must begin with base only when local class contains an override or implementation.

✔

public virtual string JoinName(string first, string last)
{
    return $"Base: {first} {last}";
}
      
public override string JoinName(string first, string last)
{
    return $"This: {first} {last}";
}
      
string thisName = this.Join("th", "is");
string baseName = base.Join("ba", "se");

✖

public virtual string JoinName(string first, string last)
{
    return $"Base: {first} {last}";
}
      
string name = base.Join("th", "se");

• ✖ Do not split overloads
  • When a class has multiple constructors, or multiple methods with the same name, these appear sequentially, with no code in between (NOT even private members).

✔

class Application
{
    public Application()
    {
    }
          
    private Application(int x)
    {
    }
          
    public void Execute(int x)
    {
    }
          
    private void Execute(bool status)
    {
    }
          
    public void Display()
    {
    }
}

✖

class Application
{
    public Application()
    {
    }
          
    public void Execute(int x)
    {
    }
          
    private Application(int x)
    {
    }
          
    // ...
}

class Application
{
    // ...
          
    public void Execute(int x)
    {
    }
          
    public void Display()
    {
    }
          
    private void Execute(bool status)
    {
    }
}

• ✖ Do not (habitually) add new methods at the end of the class

✔

class Transfer
{
    void Connect()
    {
    }
        
    void Download()
    {
    }
        
    // Recently added method
    void Upload()
    {
    }
        
    void Notify()
    {
    }
        
    void Stop()
    {
    }
}

✖

class Transfer
{
    // ...
        
    void Stop()
    {
    }
        
    // Recently added method
    void Upload()
    {
    }
}

Modifiers

• ✔ Use proper order of items
  • Within a class, struct, or interface order by group:
    • Constant Fields
    • Fields
    • Constructors
    • Finalizers (Destructors
    • Delegates
    • Events
    • Enums
    • Interfaces (Interface implementations)
    • Properties
    • Indexers
    • Methods
    • Structs
    • Classes
  • Withing each group order by access:
    • public
    • internal
    • protected internal
    • protected
    • private protected
    • private
  • Within each access groups, order by static, then non-static:
    • static
    • non-static
  • Then, order by readonly, then non-readonly:
    • readonly
    • non-readonly

class Application
{
    public const int const1 = 1;
    internal const int const2 = 2;
    protected internal const int const3 = 3;
    protected const int const4 = 4;
    private protected const int const5 = 5;
    private const int const6 = 6;

    public static readonly int field1;
    internal static readonly int field2;
    protected internal static readonly int field3;
    protected static readonly int field4;
    private protected static readonly int field5;
    private static readonly int field6;
    public static int field7;
    internal static int field8;
    protected internal static int field9;
    protected static int field10;
    private protected static int field11;
    private static int field12;
    public readonly int field13;
    internal readonly int field14;
    protected static readonly int field15;
    protected readonly int field16;
    private protected readonly int field17;
    private readonly int field18;
    public int field19;
    internal int field20;
    protected internal int field21;
    protected int field22;
    private protected int field23;
    private int field24;

    public Application(...)
    internal Application(...)
    protected internal Application(...)
    protected Application(...)
    private protected Application(...)
    private Application(...)
            
    // ...
}

• ✔ Declare access modifiers
  • It is allowed to define elements without access modifier and C# will automatically assign an access level.
  • It is a good practice to explicitly define an access modifier for each element. This removes the need for the reader to make assumptions about code and improves readability.

✔

public class A
{
    private A()
    {
    }

    private void Method()
    {
    }
}

✖

class A
{
    A()
    {
    }

    void Method()
    {
    }
}

Documentation

• ✔ Precede documentation elements with a (single) blank line

✔

int First { get; set; }

/// <summary>
/// ...
/// </summary>
int Second { get; set; }

✖

int First { get; set; }
/// <summary>
/// ...
/// </summary>
int Second { get; set; }

• ✖ Do not follow documentation elements with blank line(s)

✔

/// <summary>
/// ...
/// </summary>
int First { get; set; }

✖

/// <summary>
/// ...
/// </summary>
    
int First { get; set; }

• ✔ Documentation header must begin with a single space
  • Header lines should begin with a single space after the three leading forward slashes.

✔

/// <summary>
/// ...
/// </summary>
void Method();

✖

///<summary>
///...
///</summary>
void Method()

Regions

• ✖ Do not use regions. Seriously!
  • Try to avoid using regions. If you are already doing it, do it right!
  • In many editors, including VS, the regions will appear collapsed by default, hiding the code within the region.
  • It is generally a bad practice to hide code, as this can lead to bad decisions as the code is maintained over time.

✔

(Ctrl + M, O) - Collapse to definitions
(Ctrl + M, L) - Toggle all outlining

• ✖ Do not place regions within elements
  • Code should not contain region(s) within the body of a code statement.

✔

#region
void Method()
{
    // ...
}
#endregion

✖

void Method()
{
    #region
    // ...
    #endregion
}

• ✖ Do not write embedded regions
  • Do not write regions between declaration of statement and opening curly brackets.
  • Place regions outside statement body.

✔

#region
void Method()
{
}
#endregion

✖

void Method()
#region
{
}
#endregion

void Method()
#region
{
#endregion
}

Comments

Good code is its own best documentation. As you’re about to add a comment, ask yourself, “How can I improve the code so that this comment isn’t needed?” Improve the code and then document it to make it even clearer. — Steve McConnell

• ✔ Write self-documenting code and ignore the rest of this section. Seriously!
• ✔ Write comments in English.
• ✔ Comments longer than a word are capitalized and use punctuation.
• ✖ Do not add empty comments
• ✖ Avoid writing comments to explain bad code. Refactor the code to make it self-explanatory.
• ✔ Begin single-line comments with a single space

✔

// Single-line comment

✖

//Single-line comment
//  Single-line comment

• ✔ Write single-line comments properly
  • Single-line comments should always be preceded by a single blank line.
  • Single-line comments should never be followed by blank line(s).

✔

int x;
      
// ...
int y;

✖

int x;
      
// This comment is not valid
      
int y;

int x;
// This comment is not valid
      
int y;

• ✖ Do not write embedded comments
  • Do not write comments between declaration of statement and opening curly brackets.
  • Place comments above statements, or within statement body.

✔

// This method does something..
void Method()
{
}

✖

void Method() // This method does something..
{
}

void Method()
// This method does something..
{
}

• ✔ Use four forward slashes to indicate commented-out code
  • To differentiate comments from commented-out code, use four forward slashes.
  • Do not add space(s) between slashes and code.

✔

int Method()
{
    ////int result = 1 + 2;
    ////return result;
          
    // ...
    return 2 + 1;
}

✖

int Method()
{
    //int result = 1 + 2;
    //return result;
          
    // ...
    return 2 + 1;
}

• ✔ Use Task List friendly comments
  • Using the Task List
  • To open the Task List window in Visual Studio use Ctrl + \, T
  • Use TODO to note missing features or functionality that should be added later.
  • Use HACK to note code where questionable coding practices were used.

✔

void Method()
{
    // TODO: ...
          
    int x = 10;
    int y = 20;
          
    // TODO: ...
}

Spacing and readability

Tabs and line break

• ✖ Do not use tabs
  • The length of the tab character can vary depending upon the editor used to view the code.
  • This can cause spacing and indexing of the code to vary from the developer’s intent and can make the code difficult to read and understand.
  • Each level of indentation should consist of four spaces.

✔

var x = Method(
    100,
    200,
    300);

✖

var x = Method(
               100,
               200,
               300);
var y = Method(
        100,
        200,
        300);

• ✔ Remove unnecessary code
  • Remove any code which once removed does not change the overall logic of the code.
  • Remove duplicate code.

✔

int x = 1 + 2;

✖

try
{
    int x = 1 + 2;
}
catch (Exception ex)
{
}

• ✔ Break lines correctly
  • Break:
    • . – before dot separator
    • , – after comma
    • => – after lambda operator
    • { – before opening curly brackets for in-line initialization
    • before logical operators
  • Split method arguments by the following rule: all on same line, or all on own line.

✔

Method(arg1, arg2, arg3);

await Method(
    arg1, arg2, arg3);

var x = Method(
    arg1,
    arg2);

if ((expression1 || expression2)
    && (expresion3 && expression4)
    || expression5
    || expression6)

var x = collection
    .Where(item => item.RegisterDate.Year > 2000)
    .Join(
        collection2,
        collection1 => new { Date = collection1.RegisterDate, Owner = collection1.RegisteredBy },
        collection2 => new { Date = collection2.Date, Owner = collection2.User },
        (collection1, collection2) => new { OldEntry = collection1, NewEntry = collection2 })
    .Select(pair =>
        new
        {
            Id = pair.OldEntry.Id,
            X = pair.OldEntry.X,
            Y = pair.NewEntry.Y
        })
    .ToList();

✖

var x = collection
    .Join(collection2, // DO NOT
        collection1 => new { Date = collection1.RegisterDate, Owner = collection1.RegisteredBy }),
        collection2 => new { Date = collection2.Date, Owner = collection2.User },
        (collection1, collection2) => new { OldEntry = collection1, NewEntry = collection2 })
// ...

var x = collection
    .Where(item => item.RegisterDate.Year > 2000)
    .Select(item => item.Id).ToList(); // DO NOT

var x = collection.Where(item => item.RegisterDate.Year > 2000) // DO NOT
    .Join(
// ...

Curly brackets

• ✔ Space curly brackets correctly
  • Opening curly brackets should be preceded by a single space, unless it’s part of a method call.
  • Opening curly brackets should be followed by a single space, unless it’s the last character on the line.
  • Closing curly brackets should be followed by a single space, unless it’s the last character on the line, or it’s followed by closing parenthesis, comma, or semicolon.
  • Closing curly brackets should be preceded by a single space, unless it’s the first character on the line.

✔

void Method()
{
}

var x = Method({ 1, 2 }, 3);
var x = Method({ 1, 2 } + { 3, 4 }, 5);

int[] ints = new[] { 1, 2, 3 };
int[] ints = new[] {1, 2, 3}; // Generally accepted, but be consistent!

var x = new { X = 1, Y = "2" };
var x = new
{
    X = 1,
    Y = "2"
};

✖

void Method() { }
void Method() {
}
void Method()
{}
void Method()
{ }

var x = Method( { 1, 2 } , 3);
var x = Method( { 1, 2 } + { 3, 4 } , 5);

int[] ints = new[]{ 1, 2, 3 };

var x = new{X = 1, Y = "2"};

• ✔ Follow closing curly brackets by a blank line
  • Ensure a blank line follows closing curly brackets.

✔

void Method()
{
    if (...)
    {
    }
}

✖

void Method()
{
    if (...)
    {
    }}

• ✖ Do not wrap elements in opening and closing curly brackets
  • Write elements so they expand across multiple lines.
  • Exception: accessors within properties, events, or indexers.

✔

int Property { get; set; }

if (...)
{
    return true;
}

✖

if (...) { return true; }

• ✖ Do not follow or precede opening curly brackets with a blank line
  • Opening curly brackets should always be followed by statements, not blank line(s).
  • Opening curly brackets should never be preceded by blank line(s).

✔

void Method()
{
    // ...
}

✖

void Method()
      
{
      
    // ...
}

• ✖ Do not follow or precede closing curly brackets with a blank line
  • Closing curly brackets should always be preceded by statements, not blank line(s).
  • Closing curly brackets should never be followed by blank line(s).

✔

void Method()
{
    // ...
}

✖

void Method()
{
    // ...
      
}
       

Square brackets

• ✔ Space square brackets correctly
  • Opening square brackets should never be followed by a whitespace, unless it’s the last character on the line.
  • Opening square brackets should never be preceded by a whitespace, unless it’s the first character on the line.
  • Closing square brackets should never be preceded by a whitespace, unless it’s the first character on the line.
  • Closing square brackets should never pe followed by a whitespace, except when it’s followed by certain operators, or it is part of an array initialization.

✔

int x = array[10];
int x = array[10] + 1;
int x = matrix[10, 10];

int[] array = new int[2];
int[] array = new int[] { 1, 2, 3 };
int[] array = new[] { 1, 2, 3 };
int[,] matrix = new int[2, 2];

✖

int x = array [10];
int x = array[10]+1;
int x = matrix [10,10];

int [] array = new int[2];
int[] array = new int [] { 1, 2, 3 };
int[] array = new [] { 1, 2, 3 };

Parenthesis

• ✔ Space parenthesis correctly
  • Opening parenthesis should not be preceded by a whitespace, unless it is the first character on a line.
  • Opening parenthesis is allowed to be preceded by whitespace when it’s preceded by certain C# keywords (if, while, for etc..).
  • Opening parenthesis is allowed to be preceded by whitespace when it follows an operator symbol within an expression.
  • Closing parenthesis should not be followed by a whitespace.
  • Closing parenthesis is not allowed to be followed by whitespace when it comes at the end of a cast.
  • Closing parenthesis is allowed to be followed by whitespace when it’s followed by certain operator symbols.

✔

void Method();

int x = (a + b) * c;
int x = a / (b - c);

int x = (int)((a + b) % c);

if (a == b)

Method(Math.Max(1, 2), Math.Sqrt(144));

LongMethodCall(
    (200 - 144) * 3
    + (999 / 18),
    1,
    2);

✖

void Method ()

int x = (a + b)*c;
int x = a/(b - c);

int x = (int) ((a + b) % c);

if(a == b)

Method( Math.Max(1, 2) , Math.Sqrt(144) );

• ✔ Open parenthesis on declaration line
  • The opening parenthesis in a call to a method must be placed on same line as the method.
  • The opening parenthesis in a call to an indexer must be placed on same line as the indexer name.
  • The opening parenthesis in a method declaration must be placed on same line as the method.
  • The opening parenthesis in an indexer declaration must be placed on same line as the indexer name.

✔

bool Method(int x, int y);

bool isTrue = Method();

int x = array[0];

int this[int x]
{
    get => array[x];
}

✖

bool Method
(
    int x,
    int y
);

• ✔ Close parenthesis on line with last parameter
  • The closing parenthesis in a call to a method must be placed on same line as the last parameter.
  • The closing parenthesis in a call to an indexer must be placed on same line as the last parameter.
  • The closing parenthesis in a method declaration must be placed on same line as the last parameter.
  • The closing parenthesis in an indexer declaration must be placed on same line as the last parameter.

✔

bool Method(int x, int y);;

bool isTrue = Method();

int x = array[0];

int this[int x]
{
    get => array[x];
}

✖

bool Method
(
    int x,
    int y
);

bool isTrue = Method(
    100
);

int x = matrix[
    1,
    2
];

• ✖ Do not use unnecessary parenthesis
  • It is possible to insert parenthesis around virtually any type of expression, statement, or clause.
  • Excessive parenthesis can have a negative effect, making it more difficult to read and maintain code.

✔

int x = y + z;
string y = this.Method().ToString();

return a + b;
return x.Value;

✖

int x = (y + z);
string y = (this.Method()).ToString();

return (a + b);
return (x.Value);

Symbols

• ✔ Space symbols correctly
  • Symbols: colons, operators (arithmetic, assignment, conditional, logical, relational, shift, lambda)
  • Symbols should always be surrounded by a single space on either side.
  • Unary operators should be preceded by a single space, but must never be followed by any space.
  • Exception: Unary operators preceded or followed by a parenthesis or bracket, when there should be no spaces.

✔

int x = y + z;

bool isTrue = (x == y);
bool isTrue = (x > y);
bool isTrue = (x < y);
bool isTrue = (x >= y);
bool isTrue = (x <= y);
bool isTrue = (x != y);

int shift = 1 << 32;

Func<int, int, int> sum = (x, y) => x + y;

var x = collection
    .Where(item => item.Value >= 100)
    .ToList();

if (!value)
if (!(expression1 && expression2))

bool x = !expression;

✖

int x = y+z;

bool isTrue= (x == y);
bool isTrue =(x > y);
bool isTrue = (x< y);
bool isTrue = (x >=y);
bool isTrue = (x<=y);
bool isTrue=(x!=y);

int shift = 1<<32;

Func<int, int, int> sum = (x, y)=>x + y;

var x = collection
    .Where(item=>item.Value>=100)
    .ToList();

if ( !value)
if ( ! value)
if (! (expression1 && expression2))

bool x=!expression;
bool x =! expression;

• ✔ Space commas correctly
  • Commas should always be followed by a single space, unless it is the last character on the line.
  • Commas should never be preceded by any whitespace.

✔

void Method(int x, int y, int z);
void Method(
    int x,
    int y,
    int z);

Method(x, y, z);

✖

void Method(int x,int y,int z);
void Method(int x ,int y ,int z);
void Method(int x , int y , int z);

void Method(
    int x
    ,int y
    , int z);

• ✔ Space semicolons correctly
  • Semicolons should always be followed by a space, unless it is the last character on the line.
  • Semicolons should never be preceded by any whitespace.

✔

int X { get; set; }

string s = "semicolons";

for (int i = 0; i < 10; ++i)

✖

int X { get ; set ; }

string s = "semicolons" ;

for (int i = 0;i < 10;++i)
for (int i = 0 ; i < 10 ; ++i)

• ✔ Space colons correctly
  • Colons should never be the only element on a single line.
  • Colons appearing within an element declaration must always have a single space on either side, unless it’s the first character on the line.
  • Colons used in a conditional statement must always contain a single space on either side, unless it’s the first character on the line.
  • Colons appearing at the end of a case statement should never be preceded by a whitespace.
  • Colons appearing at the end of a case statement should always be the followed by a whitespace, or be last character on the line.

✔

class B<T> : A
    where T : class
{
    B(int x)
        : base(x)
    {
    }
}

int x = isTrue ? y : z;
int x = isTrue
    ? y
    : z;

switch (x)
{
    case 1:
        y = 1;
        break;
    case 2:
        break;
    default:
        y = 100;
        break;
}

✖

class B<T>:A
    where T:class
{
    B(int x):base(x)
    {
    }
}

int x = isTrue?x:y;
int x = isTrue
    ?
    x
    :
    y;

switch (x)
{
    case 1 :
        y = 1;
        break;
    case 2: break; // Accepted, but should be avoided. Be consistent!
    default :
        y = 100;
        break;
}

• ✔ Space increment and decrement correctly
  • The should be no whitespace between the increment or decrement symbol and the item is being incremented or decremented.

✔

int x = ++y;
int x = y++;
int x = --y;
int x = y--;
int x = y++ + ++z;

✖

int x = ++ y;
int x = y ++;
int x = -- y;
int x = y --;
int x = y ++ + ++ z;

• ✔ Space member access correctly
  • Member access symbol should never have whitespace on either side, unless it’s the first character on the line.

✔

int x = this.count;

var x = this.tuple.Item1;

var ids = collection.Select(item => item.Id).ToList();

var ids = collection
    .Select(item => item.Id)
    .ToList();

✖

int x = this. count;
int x = this .count;
int x = this . count;

var ids = this .tuple .Item1;

var ids = collection.
    Select(item => item.Id).
    ToList();

• ✖ Do not space nullable type symbols
  • Nullable type symbol should never be preceded by whitespace, unless the symbol is the first on the line.

✔

DateTime? date;

DateTime? start = new DateTime(2000, 1, 1);
DateTime? end = new DateTime(3000, 1, 1);
var range = new { start, end };

int startYear = range.start?.Year ?? 2000;
int endYear = range
    .end
    ?.Year ?? 3000;

✖

DateTime ? date;

DateTime? start = new DateTime(2000, 1, 1);
DateTime? end = new DateTime(3000, 1, 1);
var range = new { start, end };

var startYear = range.start ? .Year ?? 2000;
var endYear = range
    .end?
    .Year ?? 2000;

Signs

• ✔ Space positive sign correctly
  • Positive sign should always be preceded by a single space.
  • Positive sign should never be the last character on a line.
  • Exception when it is:
    • the first character after an opening square bracket
    • the first character after an opening parenthesis
    • the first character on the line

✔

x += y;

int x = dictionary[+y];

int x = Method(
    (999 / 9)
    + 10_000,
    -11);

string s = "First" + "Middle" + "Last";
string s = "First"
    + "Middle"
    + "Last";

✖

x+= y;

int x = dictionary[ +y ];

int x = Method(
    (999 / 9) +
    10_000,
    -11);

string s = "First"+"Middle"+"Last";
string s = "First" +
    "Middle" +
    "Last";

• ✔ Space negative sign correctly
  • Negative sign should always be preceded by a single space.
  • Negative sign should never be the last character on a line.
  • Exception when it is:
    • the first character after an opening square bracket
    • the first character after an opening parenthesis
    • the first character on the line

✔

int x = -y;
int x = -(y + z);

x -= y;

int x = dictionary[-y];

int x = Method(-y, -z);

int x = Method(
    -y, -z);
        
int x = Method(
    -y,
    -z);
        
int x = Method(
    (900 + 99)
    - 888,
    -77);

✖

int x =-y;
int x =-(y + z);

x-= y;

int x = dictionary[ -y ];

int x = Method( -y, -z);

int x = Method(
    999,
     -88,
     -7);
        
int x = Method(
    (900 + 99) -
    888,
    -77);

Layout

• ✖ Never align code
  • Alignment improves readability.. for a minute, or so. In reality, alignment creates problems for future maintenance!
  • A future change that needs to touch just one line of code will leave the formerly-pleasing formatting mangled.
  • The smallest change, as a variable rename, will break your neatly formatted code.
  • There should be no need to modify that extra piece of code. If the case raises it will be, most likely, left behind.
  • These blocks of code can slow down reviewers and exacerbates merge conflicts.

✔

int count; // Allowed comment
string name; // Allowed comment

// Allowed!
if (expression1
    && expression2)

✖

int count;   // Alligned
string name; // comments

int activeItems;   // Will no longer
string name; // be aligned after future edits

public  int     count;
private string  name;

private readonly  int     count;
private string  name;

public  int     count;
protected DateTime releaseDate;
private string  name;

void Method(int argument1,
            int argument2);
void MethodRename(int argument1,
            int argument2);

var x = collection
    .Where(i => i.Date.Year > 2000
                && i.Owner == User)
    .ToList();
var x = collection
    .Where(currentItem => currentItem.Date.Year > 2000
                && currentItem.Owner == User)
    .ToList();

• ✔ Separate elements by a blank line
  • Add a blank line between adjacent elements.

✔

Constructor()
{
}

void Method1()
{
}

void Method2()
{
}

✖

Constructor()
{
}
void Method1()
{
}
void Method2()
{
}

• ✖ Do not use multiple blank lines in a row
  • To improve code readability, blank lines are required in certain situations, but are prohibited in others.
  • This results in a consistent visual pattern and can improve recognition of unfamiliar code.
  • Use a single blank line to separate logic blocks in methods, or file sections.

✔

class Application
{
    int x;
          
    bool Method()
    {
        var one = MethodOne();
        var two = MethodTwo();
              
        return one != two;
    }
}

✖

class Application
{
    int x;
          
          
    bool Method()
    {
        var one = MethodOne();
        var two = MethodTwo();
              
              
        return one != two;
    }
}

• ✖ Do not leave blank lines at start or end of a file
  • Files should not start with one, or more blank lines.
  • Files should not end with multiple blank lines.

✔

using System;

namespace Program
{
}

✖

       
using System;

namespace Program
{
}
       
       

Parameters

• ✔ Split parameter list correctly
  • Parameters must be placed all on one line, or each on a separate line.

✔

void Method(int x, int y, int z)

void Method(
    int x, int y, int z)

void Method(
    int x,
    int y,
    int z)

✖

void Method(int x, int y,
    int z)

void Method(
    int x,
    int y, int z)

• ✔ Parameter list must follow declaration
  • The start of the parameter list of a method or indexer must begin on same line or next line of the opening parenthesis.

✔

void Method(int x, int y, int z)

void Method(
    int x, int y, int z)

void Method(
    int x,
    int y,
    int z)

✖

void Method(int x, int y,
          
    int z)

void Method(

    int x, int y, int z)

void Method(

    int x,
    int y,
    int z)

• ✔ Parameters must follow comma
  • Parameters must be written on same, or next line as previous parameter.

✔

void Method(
    int x,
    int y,
    int z)

✖

void Method(
    int x,

    int y,

    int z)

• ✔ Ensure comma is on same line as previous parameter

✔

Method(
    x,
    y,
    z);

✖

Method(
    x
    , y
    ,z);

• ✖ Do not span one parameter on multiple lines
  • Ensure parameters do not span multiple lines.
  • This ensures method calls don’t become excessively complicated, or unreadable.
  • Exceptions:
    • The first parameter is allowed to span across multiple lines.
    • Anonymous methods passed as parameter is always allowed to span multiple lines.

✔

return JoinStrings(
    "a very long string.."
    + "concatenated with another very long string...",
    "second parameter goes here");

return JoinStrings(
    "x",
    "y" + "z");

✖

return JoinStrings(
    "x",
    "y"
    + "z");

Misc

• ✔ Space keywords correctly

✔

if (...)
while (...)
for (...)
switch (...)

return -1;

throw new Exception("...");

var integers = new[] { 1, 2, 3 };

✖

if(...)
while(...)
for(...)
switch(...)

return-1;

var integers = new [] { 1, 2, 3 };

Keyword	Followed by space
catch	Yes
fixed	Yes
for	Yes
foreach	Yes
from	Yes
group	Yes
if	Yes
in	Yes
into	Yes
join	Yes
let	Yes
lock	Yes
orderby	Yes
return	Yes
select	Yes
stackalloc	Yes
switch	Yes
throw	Yes
using	Yes
where	Yes
while	Yes
yield	Yes
checked	No
default	No
sizeof	No
typeof	No
unchecked	No
new (ctor)	Yes
new (array)	No

• ✔ Space attributes correctly
  • Opening attribute brackets should never be followed by whitespace.
  • Closing attribute brackets should never be preceded by whitespace.

✔

[Attribute]
void Method()

[Attribute1]
[Attribute2]
void Method()

[Attribute1, Attribute2]
void Method()

✖

[ Attribute1]
[Attribute2 ]
[ Attribute3 ]
void Method()

[ Attribute1, Attribute2 ]
void Method()

• ✔ Space operator keyword correctly
  • The operator keyword should always be preceded and followed by a single space.

✔

Space operator +(Space space1, Space space2)

✖

Space operator+(Space space1, Space space2)

• ✖ Do not precede preprocessor keywords by space
  • Preprocessor directives should not be preceded by space(s).

✔

#if debug
#endif

✖

#  if debug
# endif

Types and variables

• ✖ Do not use underscores in identifiers
  • c-sharpcorner.com article
  • Discards, introduced in C# 7.0, are the only exception.

✔

private int x;

private readonly IDependencyInjection dependencyInjection;

var x = list1
    .Join(list2, l1 => l1.Id, l2 => l2.Id, (l1, _) => l1)
    .ToList();

services.AddScope<ISignature>(_ => new Implementation(99));

✖

private int m_x;
private int _x;

private readonly IDependencyInjection _dependencyInjection;

• ✔ Fields must be private
  • For maintainability reasons, properties should always be used as the mechanism for exposing fields outside of a class.
  • This allows the internal implementation of the property to change over time without changing the interface of the class.
  • Exception: fields within structs are allowed to have any access level.

✔

private int count;

public int Count
{
    get => this.count;
    set => this.count = value;
}

✖

public int count;

• ✔ Use built-in type alias

Alias	Type	Fully qualified type
bool	Boolean	System.Boolean
byte	Byte	System.Byte
char	Char	System.Char
decimal	Decimal	System.Decimal
double	Double	System.Double
short	Int16	System.Int16
int	Int32	System.Int32
long	Int64	System.Int64
object	Object	System.Object
sbyte	SByte	System.SByte
float	Single	System.Single
string	String	System.String
ushort	UInt16	System.UInt16
uint	UInt32	System.UInt32
ulong	UInt64	System.UInt64

1. Use predefined type names, instead of system type names.
2. Do not use basic types.
3. Do not use full namespace for types.

✔

int index;
bool isTrue;
object obj;
string name;

✖

Int32 index;
Boolean isTrue;
Object obj;
String name;

• ✔ Use shorthand for nullable types
  • Define nullable types using the C# shorthand/predefined types.

✔

int? count;
DateTime? date;

✖

Nullable<int> count;
Nullable<DateTime> date;

• ✖ Do not use Hungarian notation, or type identification in identifiers

✔

int age;
string address;
DateTime dateOfBirth;
List<Person> persons;

✖

int iAge;
string strAddress;
List<Person> personList;

• ✖ Do not use abbreviations
  • Exceptions:
    • common names and notations: Id, Url, Ftp, Xml, Http, etc..
    • for statement initializer(s)

✔

IConfiguration configuration;
DateTimeOffset dateTimeOffset;
CancellationToken cancellationToken;
string name;

UserId userId;
XmlDocument xmlDocument;
HtmlHelper htmlHelper;

✖

IConfiguration cfg;
DateTimeOffset offset;
CancellationToken ct;
string s;

Expressions

• ✔ Conditional expressions must declare precedence
  • C# maintains a hierarchy of precedence for conditional operators.
  • It is allowed to string multiple operations together on one statement and the compiler will automatically set the order based on per-established rules.
  • In order to achieve full understanding of the code, the developer must know and understand the basic operator precedents rules in C#.
  • To increase readability and maintainability and reduce the risk of introducing bugs later, it is recommended to insert parenthesis to explicitly declare the operator precedence.
  • Inserting parenthesis makes the code more obvious and easy to understand, and removes the need for the reader to make assumptions about the code.

✔

if (x || (y && z && a) || b)

return a || (b && c);
return a || b;

✖

if (x || y && z && a || b)

return a || b && c;
return (a || b);

• ✔ Arithmetic expressions must declare precedence
  • C# mentains a hierarchy of precedence for arithmetic operators.
  • It is allowed to string multiple operations together on one statement and the compiler will automatically set the order based on pre-established rules.
  • In order to achieve full understanding of the code, the developer mustt know and understand the basic operator precedente rules in C#.
  • To increase readability and maintainability and reduce the risk of introducing bugs later, it is recommended to insert parenthesis to explicitly declare the operator precedence.
  • Inserting parenthesis makes the code more obvious and easy to understand, and removes the need for the reader to make assumptions about the code.

✔

int x = 1 + ((10 % y) * a) / b) - 2;

✖

int x = 1 + 10 % y * a / b - 2;

• ✖ Do not use empty strings

✔

string s = string.Empty;

✖

string s = "";

Statements

• ✔ Write statements on a single line
  • Do not write multiple statements on the same line.
  • Do not write statements and curly brackets on the same line.

✔

int Method()
{
    int x = 1;
    int y = 2;
          
    return x + y;
}

✖

int Method()
{
    int x = 1; int y = 2;
          
    return x + y;
}

int Method() { int x = 1; int y = 2; return x + y; }

• ✖ Do not write multiple statements on one line
  • Each statement must begin on a new line.

✔

int Sum(int x, int y)
{
    int sum = x + y;
          
    return sum;
}

int a;
int b;
string firstName;
string lastName;

✖

int Sum(int x, int y)
{
    int sum = x + y; return sum;
}

int a, b;
string firstName, lastName;

• ✖ Do not write empty statements
  • Remove unneeded semicolon(s) from code.
  • Syntactically, this results in an extra, empty, statement in the code.

✔

int x = y;

✖

int x = y;;
int y = y; ;

• ✔ Chain statement blocks without blank lines
  • Some types of C# statements can only be used when chained to the bottom of another statement.
  • Remove any blank lines between chained statements.

✔

try
{   
}
catch
{
}
finally
{
}

if (...)
{
}
else
{
}

✖

try
{
}

catch
{
}

finally
{
}

if (...)
{
}

else
{
}

• ✔ Comment fall-through cases
  • Within a switch block, each statement can be terminated abruptly by break, continue, return, or throw keywords.
  • To mark statements with same result it is recommended, but not mandatory, to use an expressive comment.
  • Usually // fall through is enough.

✔

switch (x)
{
    case 1:
        // fall through
    case 2:
        HandleOneAndTwo();
        break;
    case 3:
        HandleThree();
        break
    default:
        HandleDefault();
        break;
}

switch (ch)
{
    case 'a':
    case 'e':
    case 'i':
    case 'o':
    case 'u':
    case 'A':
    case 'E':
    case 'I':
    case 'O':
    case 'U':
        HandleVowel();
        break;
    default:
        HandleConsonant();
        break;
}

✖

switch (ch)
{
    case 'a':
        // fall through
    case 'e':
        // fall through
    case 'i':
        // fall through
    case 'o':
        // fall through
    case 'u':
        // fall through
    case 'A':
        // fall through
    case 'E':
        // fall through
    case 'I':
        // fall through
    case 'O':
        // fall through
    case 'U':
        HandleVowel();
        break;
    default:
        HandleConsonant()
        break;
}

Queries and Linq

• ✔ Write all query clauses on separate lines, or all on one line
  • Query expressions should be placed on separate lines.
  • Exception: Short queries can be written on same line.

✔

var x = collection.Where(item => item.Date.Year.Equals(currentYear)).ToList();

var x = collection
    .Where(item => item.Date.Year.Equals(currentYear))
    .ToList();

var x = select a in b from c;

✖

var x = collection
    .Where(item => item.Date.Year.Equals(currentYear)).ToList();
var x = collection.Where(item => item.Date.Year.Equals(currentYear))
    .ToList();
var x = collection.Where(item => item.Date.Year.Equals(currentYear))
                  .ToList();

var x = select a
    in b from c;

• ✔ Write query clauses on multiple lines when previous clause spans multiple lines
  • Write ALL clauses on new lines when one clause spans multiple lines.

✔

var x = collection
    .Where(item => start >= item.StartDate && end <= item.EndDate)
    .Select(item => new { Id = item.Id, Name = item.Name })
    .ToList();

var x = collection
    .Where(item =>
        start >= item.StartDate
        && end <= item.EndDate)
    .Select(item => new { Id = item.Id, Name = item.Name })
    .ToList();

var x =
    select a
    in b.Method(
        2, “x”)
    from c;

✖

var x = collection
    .Where(item => start >= item.StartDate && end <= item.EndDate)
    .Select(item => new { Id = item.Id, Name = item.Name }).ToList();

var x = collection.Where(item =>
        start >= item.StartDate
        && end <= item.EndDate)
    .Select(item => new { Id = item.Id, Name = item.Name })
    .ToList();

var x =
    select a
    in b.Method(
        2, “x”) from c;

• ✔ Write query clauses on own line when spanning multiple lines
  • Query clauses must be written on own line when spanning multiple lines.

✔

var x = collection
    .Where(item => start >= item.StartDate && end <= item.EndDate)
    .Select(item => new { Id = item.Id, Name = item.Name })
    .ToList();

var x = collection
    .Where(item =>
        start >= item.StartDate
        && end <= item.EndDate)
    .Select(item => new { Id = item.Id, Name = item.Name })
    .ToList();

var x = collection
    .Where(item => start >= item.StartDate && end <= item.EndDate)
    .Select(item =>
        new
        {
            Id = item.Id,
            Name = item.Name
        })
    .ToList();

var x = collection
    .Where(item =>
        start >= item.StartDate
        && end <= item.EndDate)
    .Select(item =>
        new
        {
            Id = item.Id,
            Name = item.Name
        })
    .ToList();

var x =
    select a
    in b
    from c.Method(
        2, “x”);

✖

var x = collection.Where(item =>
        start >= item.StartDate
        && end <= item.EndDate)
    .Select(item => new { Id = item.Id, Name = item.Name })
    .ToList();

var x = collection.Select(item =>
        new
        {
            Id = item.Id,
            Name = item.Name
        })
    .ToList();

var x =
    select a
    in b from c.Method(
        2, “x”);

• ✔ Query clause must follow previous clause
  • Query clause must begin on the same line as previous clause, or on the next line.

✔

var x = select a in b from c;
var x =
    select a
    in b
    from c;

✖

var x = select a in b
    from c;
var x = select a in b
        from c;

var x = select a
        in b
        from c;
var x = select a in b
                 from c;