我收到以下错误，当我尝试编译我的C＃程序：

I get the following error when I try to compile my C# program:

类型或命名空间名称'登录'找不到（是否缺少using指令或程序集引用？）

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Windows.Forms;

namespace FootballLeague
{
    public partial class MainMenu : Form
    {
    FootballLeagueDatabase footballLeagueDatabase;
    Game game;
    Team team;
    Login login; //Error here

    public MainMenu()
    {
        InitializeComponent();
        changePanel(1);
    }

    public MainMenu(FootballLeagueDatabase footballLeagueDatabaseIn)
    {
        InitializeComponent();
        footballLeagueDatabase = footballLeagueDatabaseIn;
    }

    private void Form_Loaded(object sender, EventArgs e)
    {
    }

    private void gameButton_Click(object sender, EventArgs e)
    {
        int option = 0;
        changePanel(option);
    }
    private void scoreboardButton_Click(object sender, EventArgs e)
    {
        int option = 1;
        changePanel(option);
    }
    private void changePanel(int optionIn)
    {
        gamePanel.Hide();
        scoreboardPanel.Hide();

        string title = "Football League System";

        switch (optionIn)
        {
            case 0:
                gamePanel.Show();
                this.Text = title + " - Game Menu";
                break;
            case 1:
                scoreboardPanel.Show();
                this.Text = title + " - Display Menu";
                break;
        }
    }

    private void logoutButton_Click(object sender, EventArgs e)
    {
        login = new Login();
        login.Show();
        this.Hide();
    }

Login.cs 类：

Login.cs class:

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Windows.Forms;

namespace FootballLeagueSystem
{
    public partial class Login : Form
    {
    MainMenu menu;
    public Login()
    {
        InitializeComponent();
    }

    private void administratorLoginButton_Click(object sender, EventArgs e)
    {
        string username1 = "08247739";
        string password1 = "08247739";

        if ((userNameTxt.Text.Length) == 0)
            MessageBox.Show("Please enter your username!");
        else if ((passwordTxt.Text.Length) == 0)
            MessageBox.Show("Please enter your password!");
        else if (userNameTxt.Text.Equals("") || passwordTxt.Text.Equals(""))
            MessageBox.Show("Invalid Username or Password!");
        else
        {
            if (this.userNameTxt.Text == username1 && this.passwordTxt.Text == password1)
                MessageBox.Show("Welcome Administrator!", "Administrator Login");
            menu = new MainMenu();
            menu.Show();
            this.Hide();
        }
    }

    private void managerLoginButton_Click(object sender, EventArgs e)
    {
        {
            string username2 = "1111";
            string password2 = "1111";

            if ((userNameTxt.Text.Length) == 0)
                MessageBox.Show("Please enter your username!");
            else if ((passwordTxt.Text.Length) == 0)
                MessageBox.Show("Please enter your password!");
            else if (userNameTxt.Text.Equals("") && passwordTxt.Text.Equals(""))
                MessageBox.Show("Invalid Username or Password!");
            else
            {
                if (this.userNameTxt.Text == username2 && this.passwordTxt.Text == password2)
                    MessageBox.Show("Welcome Manager!", "Manager Login");
                menu = new MainMenu();
                menu.Show();
                this.Hide();
            }
        }
    }

    private void cancelButton_Click(object sender, EventArgs e)
    {
        this.Close();
    }

    }
}

在哪里错误？我究竟做错了什么？

Where is the error? What am I doing wrong?

推荐答案

您没有登录类是作为参考的命名空间。

You don't have the namespace the Login class is in as a reference.

添加以下为使用登录类的形式：

Add the following to the form that uses the Login class:

using FootballLeagueSystem;

当你想在其他使用类的命名空间，你必须告诉编译器在哪里可以找到它。在这种情况下，登录是 FootballLeagueSystem 命名空间中，或： FootballLeagueSystem.Login 是完全合格的命名空间的。

When you want to use a class in another namespace, you have to tell the compiler where to find it. In this case, Login is inside the FootballLeagueSystem namespace, or : FootballLeagueSystem.Login is the fully qualified namespace.

作为一个评论者指出的那样，你声明的 FootballLeagueSystem 命名空间内登录类，但你使用它的 FootballLeague 命名空间。

As a commenter pointed out, you declare the Login class inside the FootballLeagueSystem namespace, but you're using it in the FootballLeague namespace.