关闭表格的C＃问题

Question

I have been experiencing problems with closing the Log In form when I have switched to 2nd form on successful Log In. I tried .close and .dispose , but the Log in Form wouldn't close. Following is my code.

namespace Lead_Management_Pro
{
    public partial class FrmLogin : Form
    {
        Form1 mainform;
        public FrmLogin()
        {
            InitializeComponent();
        }

        public void button1_Click(object sender, EventArgs e)
        {
            FrmLogin frm = new FrmLogin();
            mainform = new Form1();
            string[] v;

            OleDbConnection conn = new OleDbConnection("File Name=E:\\Vivek\\License Manager\\License Manager\\login.udl");

            try
            {
                conn.Open();

                string query = "EXEC dbo.checkuser '" + username.Text+ "', '" + password.Text+"'";
                OleDbCommand cmd = new OleDbCommand(query, conn);
                string s = Convert.ToString(cmd.ExecuteScalar());
                v= s.Split('|');
                if (v[0]=="0")
                {

                    frm.Close();
                    mainform.ShowDialog();
                }
                else
                {
                    MessageBox.Show("Please enter correct user credentials and try again");
                }
            }
            catch (Exception ex)
            {
                MessageBox.Show(ex.Message);
            }

            conn.Close();
        }

        private void button2_Click(object sender, EventArgs e)
        {
            this.Close();
        }
    }
}

Please help me to rectify the issue.

Answer 1

frm.Close() closes the instance you are making. you should use this.Close(); like the one you did in button2_Click event

Update 2

FrmLogin is your startup form. Try hiding it:

if (v[0]=="0")
{
    mainform.Show();
    this.Hide();
}

Answer 2

I had a similar issue in one of my projects. The problem is that if you open your login form as your first form, it's viewed as the main form, and when you close it, the program starts shutting down because you closed your main form.

What you need to do is open your login form from the context of your Form1 main form, instead of opening your main form from the context of your login form.

in pseudocode:

public Form1(){
    if(not logged in)
    {
        FrmLogin login = new FrmLogin();
        login.ShowDialog();//This blocks the further execution of the Form1 constructor until you're out of the window
    }
    InitializeCompent();
}

Handle your login procedure in your Login form and close the form in there once you're logged in. It will automatically continue on to the rest of your Form1 constructor and open it through there. You might want to have a check after executing your login whether you're actually logged in, and shut down if you're not.