C# 错误：“命名空间不能直接包含字段或方法等成员”

Question

A method receiving 2 numbers and I need to return the numbers of common digits for them. For example, the numbers 2201 and 3021 returns 3 because these numbers have 3 common digits: 0, 1, and 2.

I get this error and don't understand it: A namespace cannot directly contain members such as fields or methods

Here is the code:

public static int AlphaRomeo(int a, int b)
{
    int count = 0;
    while (a > 0)
    {
        int tempa = a % 10;
        a = a / 10;
        int tempb = b % 10;
        b = b / 10;
        if (tempa == tempb)
            count++;
    }
    return count;

}

Answer 1

Might be easier to avoid the mathematics:

private static string _digits = "0123456789";

public static int AlphaRomeo(int a, int b)
{
    string aStr = a.ToString();
    string bStr = b.ToString();
    int common = 0;

    for (int i = 0; i < _digits.Length; i++)
    {
        if (aStr.Contains(_digits[i]) && bStr.Contains(_digits[i]))
            common++;
    }

    return common;
}

Answer 2

Consider this example, you don't have a class in your code:

using System;  // Imports

namespace LearnClasses    // Namespace
{
    class Program    //class
    {
        static void Main(string[] args)   // Method 1
        {
           Console.WriteLine( AlphaRomeo(2201, 3021));
        }

        public static int AlphaRomeo(int a, int b)  // Method 2
        {
            int count = 0;
            // Your code
            return count;
        }
    }
}