This documentation is archived and is not being maintained.

C# Coding Conventions (C# Programming Guide)

The C# Language Specification does not define a coding standard. However, the guidelines in this topic are used by Microsoft to develop samples and documentation.

Coding conventions serve the following purposes:

  • They create a consistent look to the code, so that readers can focus on content, not layout.

  • They enable readers to understand the code more quickly by making assumptions based on previous experience.

  • They facilitate copying, changing, and maintaining the code.

  • They demonstrate C# best practices.

  • Naming guidelines are covered in Guidelines for Names.

  • You do not have to change the names of objects created by the Visual Studio designer tools to make them fit the guidelines.

  • In short examples that do not include using directives, use namespace qualifications. If you know that a namespace is imported by default in a project, you do not have to fully qualify the names from that namespace. Qualified names can be broken after a dot (.) if they are too long for a single line, as shown in the following example.

    var currentPerformanceCounterCategory = new System.Diagnostics.

Good layout uses formatting to emphasize the structure of your code and to make the code easier to read. Microsoft examples and samples conform to the following conventions:

  • Use the default Code Editor settings (smart indenting, four-character indents, tabs saved as spaces). For more information, see Formatting, C#, Text Editor, Options Dialog Box.

  • Write only one statement per line.

  • Write only one declaration per line.

  • If continuation lines are not indented automatically, indent them one tab stop (four spaces).

  • Add at least one blank line between method definitions and property definitions.

  • Use parentheses to make clauses in an expression apparent, as shown in the following code.

    if ((val1 > val2) && (val1 > val3))
        // Take appropriate action.

  • Place the comment on a separate line, not at the end of a line of code.

  • Begin comment text with an uppercase letter.

  • End comment text with a period.

  • Insert one space between the comment delimiter (//) and the comment text, as shown in the following example.

    // The following declaration creates a query. It does not run
    // the query.
  • Do not create formatted blocks of asterisks around comments.

The following sections describe practices that the C# team follows to prepare code examples and samples.

String Data Type

  • Use the + operator to concatenate short strings, as shown in the following code.

    string displayName = nameList[n].LastName + ", " + nameList[n].FirstName;
  • To append strings in loops, especially when you are working with large amounts of text, use a StringBuilder object.

    var phrase = "lalalalalalalalalalalalalalalalalalalalalalalalalalalalalala";
    var manyPhrases = new StringBuilder();
    for (var i = 0; i < 10000; i++)
    //Console.WriteLine("tra" + manyPhrases);

Implicitly Typed Local Variables

  • Use implicit typing for local variables when the type of the variable is obvious from the right side of the assignment, or when the precise type is not important.

    // When the type of a variable is clear from the context, use var 
    // in the declaration.
    var var1 = "This is clearly a string.";
    var var2 = 27;
    var var3 = Convert.ToInt32(Console.ReadLine());
  • Do not use var when the type is not apparent from the right side of the assignment.

    // When the type of a variable is not clear from the context, use an
    // explicit type.
    int var4 = ExampleClass.ResultSoFar();
  • Do not rely on the variable name to specify the type of the variable. It might not be correct.

    // Naming the following variable inputInt is misleading. 
    // It is a string.
    var inputInt = Console.ReadLine();
  • Avoid the use of var in place of dynamic.

  • Use implicit typing to determine the type of the loop variable in for and foreach loops.

    The following example uses implicit typing in a for statement.

    var syllable = "ha";
    var laugh = "";
    for (var i = 0; i < 10; i++)
        laugh += syllable;

    The following example uses implicit typing in a foreach statement.

    foreach (var ch in laugh)
        if (ch == 'h')

Unsigned Data Type

  • In general, use int rather than unsigned types. The use of int is common throughout C#, and it is easier to interact with other libraries when you use int.


  • Use the concise syntax when you initialize arrays on the declaration line.

    // Preferred syntax. Note that you cannot use var here instead of string[].
    string[] vowels1 = { "a", "e", "i", "o", "u" };
    // If you use explicit instantiation, you can use var.
    var vowels2 = new string[] { "a", "e", "i", "o", "u" };
    // If you specify an array size, you must initialize the elements one at a time.
    var vowels3 = new string[5];
    vowels3[0] = "a";
    vowels3[1] = "e";
    // And so on.


  • Use the concise syntax to create instances of a delegate type.

    // First, in class Program, define the delegate type and a method that  
    // has a matching signature.
    // Define the type.
    public delegate void Del(string message);
    // Define a method that has a matching signature.
    public static void DelMethod(string str)
        Console.WriteLine("DelMethod argument: {0}", str);
    // In the Main method, create an instance of Del.
    // Preferred: Create an instance of Del by using condensed syntax.
    Del exampleDel2 = DelMethod;
    // The following declaration uses the full syntax.
    Del exampleDel1 = new Del(DelMethod);

try-catch and using Statements in Exception Handling

  • Use a try-catch statement for most exception handling.

    static string GetValueFromArray(string[] array, int index)
            return array[index];
        catch (System.IndexOutOfRangeException ex)
            Console.WriteLine("Index is out of range: {0}", index);
  • Simplify your code by using the C# using statement. If you have a try-finally statement in which the only code in the finally block is a call to the Dispose method, use a using statement instead.

    // This try-finally statement only calls Dispose in the finally block.
    Font font1 = new Font("Arial", 10.0f);
        byte charset = font1.GdiCharSet;
        if (font1 != null)
    // You can do the same thing with a using statement.
    using (Font font2 = new Font("Arial", 10.0f))
        byte charset = font2.GdiCharSet;

&& and || Operators

  • To avoid exceptions and increase performance by skipping unnecessary comparisons, use && instead of & and || instead of | when you perform comparisons, as shown in the following example.

    Console.Write("Enter a dividend: ");
    var dividend = Convert.ToInt32(Console.ReadLine());
    Console.Write("Enter a divisor: ");
    var divisor = Convert.ToInt32(Console.ReadLine());
    // If the divisor is 0, the second clause in the following condition
    // causes a run-time error. The && operator short circuits when the
    // first expression is false. That is, it does not evaluate the
    // second expression. The & operator evaluates both, and causes 
    // a run-time error when divisor is 0.
    if ((divisor != 0) && (dividend / divisor > 0))
        Console.WriteLine("Quotient: {0}", dividend / divisor);
        Console.WriteLine("Attempted division by 0 ends up here.");

New Operator

  • Use the concise form of object instantiation, with implicit typing, as shown in the following declaration.

    var instance1 = new ExampleClass();

    The previous line is equivalent to the following declaration.

    ExampleClass instance2 = new ExampleClass();
  • Use object initializers to simplify object creation.

    // Object initializer.
    var instance3 = new ExampleClass { Name = "Desktop", ID = 37414, 
        Location = "Redmond", Age = 2.3 };
    // Default constructor and assignment statements.
    var instance4 = new ExampleClass();
    instance4.Name = "Desktop";
    instance4.ID = 37414;
    instance4.Location = "Redmond";
    instance4.Age = 2.3;

Event Handling

  • If you are defining an event handler that you do not need to remove later, use a lambda expression.

    public Form2()
        // You can use a lambda expression to define an event handler.
        this.Click += (s, e) =>
    // Using a lambda expression shortens the following traditional definition.
    public Form1()
        this.Click += new EventHandler(Form1_Click);
    void Form1_Click(object sender, EventArgs e)

Static Members

  • Call static members by using the class name: ClassName.StaticMember. Do not access a static member that is defined in a base class from a derived class.

LINQ Queries

  • Use meaningful names for query variables. The following example uses seattleCustomers for customers who are located in Seattle.

    var seattleCustomers = from cust in customers
                           where cust.City == "Seattle"
                           select cust.Name;
  • Use aliases to make sure that property names of anonymous types are correctly capitalized, using Pascal casing.

    var localDistributors =
        from customer in customers
        join distributor in distributors on customer.City equals distributor.City
        select new { Customer = customer, Distributor = distributor };
  • Rename properties when the property names in the result would be ambiguous. For example, if your query returns a customer name and a distributor ID, instead of leaving them as Name and ID in the result, rename them to clarify that Name is the name of a customer, and ID is the ID of a distributor.

    var localDistributors2 =
        from cust in customers
        join dist in distributors on cust.City equals dist.City
        select new { CustomerName = cust.Name, DistributorID = dist.ID };
  • Use implicit typing in the declaration of query variables and range variables.

    var seattleCustomers = from cust in customers
                           where cust.City == "Seattle"
                           select cust.Name;
  • Align query clauses under the from clause, as shown in the previous examples.

  • Use where clauses before other query clauses to ensure that later query clauses operate on the reduced, filtered set of data.

    var seattleCustomers2 = from cust in customers
                            where cust.City == "Seattle"
                            orderby cust.Name
                            select cust;
  • Use multiple from clauses instead of a join clause to access inner collections. For example, a collection of Student objects might each contain a collection of test scores. When the following query is executed, it returns each score that is over 90, along with the last name of the student who received the score.

    // Use a compound from to access the inner sequence within each element.
    var scoreQuery = from student in students
                     from score in student.Scores
                     where score > 90
                     select new { Last = student.LastName, score };

Follow the guidelines in Secure Coding Guidelines.