Single-line and Multi-line Comments in C#

Introduction

A comment is an annotation in a source code with the intention to give a programmer a readable explanation of the code. These annotations are ignored by compilers when compiling your code. Comments should explain, at a higher level of abstraction than the code, what you're trying to do.

C# has different syntax for comments. In this guide, we’ll look at single-line and multi-line comments.

Single-line Comment Examples

Single-line comments allow narrative on only one line at a time. Single-line comments can begin in any column of a given line and end at a new line or carriage return.

The // character sequence marks the text following it as a single-line comment. Here’s an example

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class Account
{
  private string _accountNo;

  public Account(string accountNo, int balance)
  {
    AccountNo = accountNo;
    Balance = balance;
  }

  public string AccountNo
  {
    get => _accountNo;
    set
    {
      //raise exception if value is null
      if(String.IsNullOrEmpty(value))
      throw new InvalidOperationException();
      _accountNo = value;
    }
  }

  public int Balance { get; set; }

  public void Credit(int amount)
  {
    Balance = amount + Balance; //update the balance with a summation of the inputted amount and the current balance
    //Logs the new balance to the screen
    Console.WriteLine(Balance);
  }
}

The code above uses single-line comments within the Credit method and the set accessor for the AccountNo property.

Multi-line Comment Examples

Multi-line comments have one or more lines of narrative within a set of comment delimiters. The /* delimiter marks the beginning of the comment, and the */ marks the end. You can have your comment span multiple lines and anything between those delimiters is considered a comment

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class Account
{
  /* Account class constructor.
    In it we initialise the AccountNo and Balance property.
    These properties are needed to identify an account and perform transaction using its available methods
    */
  public Account(int accountNo, int balance)
  {
    AccountNo = accountNo;
    Balance = balance;
  }

  public int AccountNo { get; set; }

  public int Balance { get; set; }

  public void Credit(int amount)
  {
    Balance = amount + Balance;
  }
}

It can also be placed inside code statements.

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var account = new Account(2 /* this is a dummy account number */, 2000);

The code above tells the reader that the number 2 is just a fake account number that should be replaced later. Be careful with the use of comments. If a code block is hard to read, endeavour to re-write to a more readable form.

That’s a Wrap!

Code comments can be extremely useful in helping you, or other programmers who will use your code, to understand your code better. It is a way of annotating source code with helpful narratives. Over-use it and you get source code that’s hard to read and understand.

We looked at single-line and multi-line comment in C#. Single-line comments end at the first end-of-line following the // comment marker. You can place it at the top of the code statement or after the code statement. If it’s after a code statement, whatever text following it is regarded as the comment. On the other hand, multi-line comments can span many lines or be placed within a code statement and only the content between the comment delimiters will be treated as the comment and ignored during compilation.