2.1.6. The risk of assignment inside an "if"

Beware of the equality operator: remember that the format is "if (a == b)" ... If we do not remember it and write "if (a = b)", we are trying to assign to "a" the value "b".

In some C compilers, this could be a serious problem, because in C language it is acceptable to assign a value within an "if" (although most modern compilers would warn us that it might be an unintended assignment).

For the C# language, such risk does not exist, because in C# the "condition" must be strictly "true" or "false", so an assignment would lead to a compile error: "Can not implicitly convert type 'int' to 'bool'". This is the case in the following program:

/*---------------------------*/
/*  C# Example #11:          */
/*  example11.cs             */
/*                           */
/*  Conditions with if (7)   */
/*    incorrect comparison   */
/*                           */
/*  Intro to C#,             */
/*    Nacho Cabanes          */
/*---------------------------*/
 
using System;
 
public class Example11
{
  public static void Main()
  {
    int number;
 
    Console.WriteLine("Enter a number");
    number = Convert.ToInt32(Console.ReadLine());
    if (number = 0) 
      Console.WriteLine("The number is zero.");
    else
      if (number < 0) 
        Console.WriteLine("The number is negative.");
      else
        Console.WriteLine("The number is positive.");
  }
}