我得到了 CS0029 C# 无法将类型“int”隐式转换为“bool”

Question

im learning and i want to make so that if the age entered is 15 it will make a special message i just started yesterday so im trying to do random things to be sure i understand but i didnt learn that yet

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace Meme
{
class Program
{
    static void Main(string[] args)
    {
        string yourName;
        Console.WriteLine("What is your name?");
        yourName = Console.ReadLine();
        Console.WriteLine("Hello {0}", yourName);
        Console.WriteLine("What is your age?");
        int yourAge = Convert.ToInt32(Console.ReadLine());
        Console.WriteLine("Hello {0}, you are {1} years old", yourName, yourAge);
        Console.WriteLine("What is your rank?");
        int yourRank;
        yourRank = Convert.ToInt32(Console.ReadLine());
        const int Y = 15;
        if ((yourAge = Y))
        {
            Console.WriteLine("NO");
        }
    }
}

}

Answer 1

C# uses == to mean "compare for equality" and = to mean "assign value to variable or property". You've mixed them up.

Moreover, in C# (and many other languages), x = y is an expression that assigns the value of y to variable x and then produces the assigned value as a result . So if (yourAge = Y) means "assign Y to yourAge , then use the integer value assigned to make the decision in the if ". But the condition of an if is required to be convertible to a bool , and int is not. Hence the error.

It would have been better to special-case this behaviour in the compiler so that accidental use of = instead of == produces a better error message. C# does so in this situation, but only this situation:

bool b = whatever;
if (b = true)

There it says, sensibly, that you are probably using = where == is intended. I wish we had made the compiler give this kind of error in more situations. (Though if (b==true) is only marginally better; the right thing to type there is if (b) !)