将登录的用户信息传递给另一种形式的C＃MySQL

Question

For example I want to display the logged in user's information from database to another form like firstname and lastname I got no problem in admin because it only has one form or details for it. I tried passing the text in textbox username to another form and then select the passed text to display the other information of it but it won't, here's my code btw.

private void button2_Click(object sender, EventArgs e)
    {
        int i = 0;
        MySqlCommand comm = con.CreateCommand();
        comm.CommandText = "select * from accountinfo where username = @user and pass = @password";
        comm.Parameters.AddWithValue("@user", textBox1.Text);
        comm.Parameters.AddWithValue("@password", textBox2.Text);
        MySqlDataReader myReader;
        con.Open();
        comm.ExecuteNonQuery();
        myReader = comm.ExecuteReader();
        string accountType = string.Empty;
        DataTable dt = new DataTable();
        MySqlDataAdapter da = new MySqlDataAdapter(comm);
        i = Convert.ToInt32(dt.Rows.Count.ToString());

       while (myReader.Read())
       {
            i = i + 1;
            accountType = myReader["accountType"].ToString();
       }
       if (i == 0)
       {
            MessageBox.Show("Wrong username or password!");
       }
       else if (accountType == "admin")
       {
            MessageBox.Show("Welcome admin");
            this.Hide();
            textBox1.Text = string.Empty;
            textBox2.Text = string.Empty;
            Form3 frm3 = new Form3();
            frm3.Show();
       }
       else
       {
            MessageBox.Show("Welcome");
            this.Hide();
           using(var frm4 = new Form4())
           {

               frm4.FirstName = textBox1.Text;
               frm4.ShowDialog();
           }
       }
            con.Close();
    }

and my code in second form

public partial class Form4 : Form
{
    public string FirstName { get; set; }
    public string LastName { get; set; }
    public string CellNo { get; set; }

    public Form4()
    {
        InitializeComponent();
    }

    private void Form4_Load(object sender, EventArgs e)
    {
        tbUser.Text = FirstName;
        try
        {
            string MyConnection2 = "server=localhost;user id=root;database=account;persistsecurityinfo=True;PASSWORD=test123;SslMode=none";
            string Query = "SELECT firstname = '" + tbFN.Text + "' from accountinfo WHERE username = '" + tbUser + "' " ; 
            MySqlConnection MyConn2 = new MySqlConnection(MyConnection2);
            MySqlCommand MyCommand2 = new MySqlCommand(Query, MyConn2);
            MySqlDataAdapter MyAdapter = new MySqlDataAdapter();
            MyAdapter.SelectCommand = MyCommand2;
            DataTable dTable = new DataTable();
            MyAdapter.Fill(dTable);
        }
        catch (Exception ex)
        {
            MessageBox.Show(ex.Message);
        } 

    }
}

Answer 1

Logged in user information is kind of static for all your application, so you should be able to access to it from anywhere

As a solution create class user

public class User {
    username, full name ...
}

Create embiend class ApplicationContext

public class ApplicationContext
{
   private ApplicationContext(){
   }

   public User UserInfo {get;}

   public static ApplicationContext Current{get;}

   public static Init(User userInfo)
   {
       if(Current != null)
           throw new Exception("Context already initialized");

       Current = new ApplicationContext(){
           UserInfo = userInfo
       }
   }
}

After login call

ApplicationContext.Init(userInfo);

Everywhere where you need user info call

ApplicationContext.Current.UserInfo