如何检查输入类型并使用 if..else 条件而不会在 c# 中出现错误

Question

我在做一个必须输入密码的项目。

using System;

namespace program.cs
{
    class Program
    {
        static void Main(string[] args)
        {
            bool checkpoint1 = false;
            long password = 99101L;
            Console.WriteLine("Write the Password to Access");
            string keyPassword = Console.ReadLine();
            if(keyPassword.Length != 0)
            {
                checkpoint1 = true;
            }
            else
            {
                Console.WriteLine("The Password you entered was blank.");
            }
            
            if (checkpoint1)

            {
                long key = Convert.ToInt64(keyPassword);
                if (key == password)
                {
                    Console.WriteLine("Access Granted!");
                }
                else
                {
                    Console.WriteLine("Password Incorrect! \n Access Denied");
                }
            }
        }

    }
}

但是当我输入一个字符串作为密码时，它会在 long key = Conver.ToInt64(keyPassword) 行抛出一个错误，它不能更改为 long，所以我该如何解决这个问题，它打印出类型是 a string，如果我尝试 getType 和 typeof() 它，无论 readline 总是接受一个字符串，它都会显示一个字符串。请帮忙。 编辑：我解决了，最终结果代码：

using System;

namespace program.cs
{
    class Program
    {
        static void Main(string[] args)
        {
            bool checkpoint1 = false;
            long password = 99101L;
            Console.WriteLine("Write the Password to Access");
            string keyPassword = Console.ReadLine();
            if(keyPassword.Length != 0)
            {
                checkpoint1 = true;
            }
            else
            {
                Console.WriteLine("The Password you entered was blank.");
            }
            
            if (checkpoint1)

            {
                if(!long.TryParse(keyPassword, out var key))
                {
                    Console.WriteLine("The Password you entered is not a number, please try again");
                }
                else
                {
                    long Realkey = Convert.ToInt64(keyPassword);
                    if (Realkey == password)
                    {
                        Console.WriteLine("Access Granted!");
                    }
                    else
                    {
                        Console.WriteLine("Password Incorrect! \n Access Denied");
                    }
                }
            }
        }

    }
}

Answer 1

您可以使用 long.TryParse:

 string keyPassword = Console.ReadLine();

 if (string.IsNullOrEmpty(keyPassword)) {
   Console.WriteLine("The Password you entered was blank.");
 } 
 else if (!long.TryParse(keyPassword, out var key)) {
   Console.WriteLine("The Password you entered is not a valid integer.");
 }  
 else if (key != password) {
   Console.WriteLine("Password Incorrect! \n Access Denied");
 }
 else { // Ugh, finally...
   Console.WriteLine("Access Granted!");
 }