C# 错误：CS0103 当前上下文中不存在名称“ ”

Question

I'm trying to call a class object made in the Main in a method outside of the Main , but it is not working. I'm new to C# so I am used to python's Def and its way different.

public class User
{
  public string name;
  public string password;
  public string notepad;
}

static void Main(string[] args)
{ 
    Console.Clear();
    Console.WriteLine("\n--------------------------\n"+"Please create a new user."+"\n--------------------------");
    Console.WriteLine("\nUsername: ");
    string x = Console.ReadLine();
    Console.WriteLine("\nPassword: ");
    string y = Console.ReadLine();
    **User xe = new User();
    xe.name = x;**

   ----removed cuz has nothing to do with the code----

    Console.WriteLine("Dashboard");
    Console.WriteLine("\nPlease choose a function by inputting the number before the name.\n1 - Notepad\n2 - Calculator");

    while(login) {
        try{
            int letter = Convert.ToInt32(Console.ReadLine());
            login = false;
            if(letter == 1) {
                Console.WriteLine("Notepad");
            }
            else if(letter == 2) {
                Console.WriteLine("Calculator");
            }
        }
        catch{
            Console.WriteLine("Please input a number.");
        }
    }
}
**public static string notepad(string np){
    np = Console.ReadLine();
    xe.notepad = np;**
}

I put ** on the parts that are giving an error.

Answer 1

I've modified your code below. I've commented the areas that I've modified. There were a few areas of concern. Most noticeably, you never called the notepad method. Also, the combined input request (convert(getinput)) kept crashing. So, I broke it up into two lines.

Since you weren't returning anything from the notepad method, I changed the return type to void. Then, I changed the method signature from notepad(string np) to notepad(User xel). This passes the xe object to the notepad method.

I've added some writelines to show where you are in the code.

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

namespace ConsoleApplication1
{
    public class User
    {
        public string name;
        public string password;
        public string notepad;
    }

    class Program
    {
        static void Main(string[] args)
        {
            // I've added this line to get around the missing login source
            bool login = true;

            Console.Clear();
            Console.WriteLine("\n--------------------------\n" + "Please create a new user." + "\n--------------------------");
            Console.WriteLine("\nUsername: ");
            string x = Console.ReadLine();
            Console.WriteLine("\nPassword: ");
            string y = Console.ReadLine();
            User xe = new User();
            xe.name = x;

            //----removed cuz has nothing to do with the code----

            Console.WriteLine("Dashboard");
            Console.WriteLine("\nPlease choose a function by inputting the number before the name.\n1 - Notepad\n2 - Calculator");

            while (login)
            {
                try
                {
                    // Here I've separated the input request, the combination of the convertion and the input mixed kept crashing.
                    string theletter = Console.ReadLine();
                    int letter = Convert.ToInt32(theletter);

                    login = false;
                    if (letter == 1)
                    {
                        Console.WriteLine("Notepad");

                        // Here I'm calling the notepad method with the xe
                        notepad(xe);
                        Console.WriteLine("\n\n* Ok, I'm back in the Main *\n");
                        Console.ReadLine();
                    }
                    else if (letter == 2)
                    {
                        Console.WriteLine("Calculator");
                    }
                }
                catch
                {
                    Console.WriteLine("Please input a number.");
                }
            }
        }

        // **** Here I've changed the return type from string to void, since it's not returning anything.
        // **** I've also added a parameter to pass the xe as xel (optional) using the proper type
        public static void notepad(User xel)
        {
            Console.WriteLine("\n\n * I'm here in the notepad method *\n");
            string np = Console.ReadLine();
            xel.notepad = np;
            Console.WriteLine("\nYou entered this for your notepad: \n");
            Console.WriteLine(np);
            Console.WriteLine("\nThis is your new notepad: \n");
            Console.WriteLine(xel.notepad);
        }
    }
}

Answer 2

You cannot access the variable xe from the method notepad because it is from the method Main() .
You can either make the xe global (putting it outside the Main() method),
or
you can pass it to notepad() as an argument. Like this:

//changed it to void cause you arent returning any value
//removed string np argument because you were not using its value (you were overriding it before you use it)
public static void notepad(User u){

  string np = Console.ReadLine();
  u.notepad = np;
}

hope it helps.