c# - 如何在单击交叉按钮时使 bool 值为 false？

Question

我正在构建一个登录表单，其中我有一个 bool 值，当用户从登录页面单击登录按钮时该值变为真。现在我希望如果用户单击交叉按钮关闭 MDI 表单，则 bool 值应该变为false 并且用户可以从登录表单再次登录。我该怎么做？在我的例子中，当我点击交叉按钮时，我无法做到这一点，它显示错误消息“您已经登录”，但如果表单关闭，它应该允许我再次登录。请帮助我摆脱困境。

Here is the code for the login form----

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

namespace Login
{
    public partial class LogIin : Form
    {
        public bool IsLoggedIn { get; set; }


        public LogIin()
        {
            InitializeComponent();
        }

        private void LogIn_Click(object sender, EventArgs e)
        {
            SqlConnection con = new SqlConnection(@"Data Source=IBMPC\SQLEXPRESS;Initial Catalog=UserData;Integrated Security=True");
            SqlCommand cmd = new SqlCommand("select * from User_Credential where UserName = @UserName and Passwords = @Passwords", con);

            cmd.Parameters.AddWithValue("@UserName", UsTxt.Text);
            cmd.Parameters.AddWithValue("@Passwords", PassTxt.Text);
            SqlDataAdapter sda = new SqlDataAdapter(cmd);


            DataTable dt = new DataTable();
            sda.Fill(dt);
            con.Open();
            int i = cmd.ExecuteNonQuery();
            con.Close();

            {

                if (!IsLoggedIn)
                {

                    if (dt.Rows.Count > 0)
                    {

                        Welcome_Form wf = new Welcome_Form();

                        wf.Show();
                        IsLoggedIn = true;
                    }
                    else
                    {
                        MessageBox.Show("Please enter Correct Username and Password");
                    }
                }
                else
                {
                    MessageBox.Show("You are already logged in", "Error");
                }

            }
        }


        private void Exit_Click(object sender, EventArgs e)
        {

            this.Close();
        }
    }
}

Answer 1

如果关闭窗口，则必须将值设置为 false。

 private void Exit_Click(object sender, EventArgs e)
    {
        IsLoggedIn = false;
        this.Close();
    }