How to Prevent Auto Closing of Forms When MainForm(Start Up) form is Closed?

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i have an c# Winform application in Visual studio ...
when my project runs Login form is opened for user that take user name and password
when user provide correct information this login form closed and Main MDI open which suddenly closed itself after a second
i want to Prevent them from auto closing
so Please can any one knows how to fix???

C#

public void login()
        {
            string a = "No";
            if (txtuser.Text != "" & txtpass.Text != "")
            {
             string queryText = "SELECT Count(*) FROM tbllogin " +
                         "WHERE username = @Username AND pass = @Password";
                using (SqlConnection cn = new SqlConnection("Server= localhost;                
database=tailoringmng; integrated Security=true"))
                using (SqlCommand cmd = new SqlCommand(queryText, cn))
                {
                    cn.Open();
                    cmd.Parameters.AddWithValue("@Username", txtuser.Text);  
                    cmd.Parameters.AddWithValue("@Password", txtpass.Text);
                    int result = (int)cmd.ExecuteScalar();
                    if (result > 0)
                    {
                        frmmainmdi mdi = new frmmainmdi();
                        a = "Yes";
                        mdi.A = "Yes";
                        mdi.Show();



                        this.Close();
                    }
                    else
                        MessageBox.Show("User Not Found!");
                }

            }
            

        }

Posted 20-Mar-14 9:45am

abdul manan 7

Updated 20-Mar-14 10:53am

v2

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Sergey Alexandrovich Kryukov 20-Mar-14 16:35pm

What is "mdi"? Do you really use MDI? Don't...
—SA

2 solutions

Solution 2

You can prevent closing main form if you handle the event FormClosing. This event is cancellable. You can cancel closing on some condition, if you assign true to the property Handled of the event arguments parameter passing. Please see:
http://msdn.microsoft.com/en-us/library/system.windows.forms.form.formclosing(v=vs.110).aspx[^],
http://msdn.microsoft.com/en-us/library/system.windows.forms.formclosingeventhandler(v=vs.110).aspx[^],
http://msdn.microsoft.com/en-us/library/system.windows.forms.formclosingeventargs(v=vs.110).aspx[^].

When you cancel the closing, you can call Hide instead.

There are differen techniques. You can close the application and start it again, in your Main<code> method (entry point). Say, you can run <code>Application.Run in cycle (or several times), with different form passing as a parameter. Sometimes it is used to give the application two main form, say, one is loging or splash, and, on second run, "real" main. Only remember: you cannot re-use truly closed form; it is disposed.

—SA

Posted 20-Mar-14 11:03am

Sergey Alexandrovich Kryukov

Updated 20-Mar-14 11:07am

v2

Comments

abdul manan 7 20-Mar-14 17:09pm

make it simple
when frmlogin close //this is may main form
the mdi stay open this is my other form which i want to make secondary main form after frmlogin
Application.EnableVisualStyles();
Application.SetCompatibleTextRenderingDefault(false);
//Application.Run(new frmmainmdi());
Application.Run(new frmLogon());

Sergey Alexandrovich Kryukov 20-Mar-14 21:03pm

When you say "mdi", what do you mean? MDI child? parent?
By "second main form" I mean one at a time. Application.Run exists, and starts again with different form...
—SA

abdul manan 7 21-Mar-14 5:15am

MDI parent

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Krunal Rohit · Accepted Answer · 2014-03-20T10:09:00

Solution 1

It seems that Login() is your main form, that is why when it is closed, other are automatically closed.. So instead what you can do is, set the visibility of the form the to false.

C#

public string login()
        {
            string a = "No";
            if (txtuser.Text != "" & txtpass.Text != "")
            {
             string queryText = "SELECT Count(*) FROM tbllogin " +
                         "WHERE username = @Username AND pass = @Password";
                using (SqlConnection cn = new SqlConnection("Server= localhost;
database=tailoringmng; integrated Security=true"))
                using (SqlCommand cmd = new SqlCommand(queryText, cn))
                {
                    cn.Open();
                    cmd.Parameters.AddWithValue("@Username", txtuser.Text);
                    cmd.Parameters.AddWithValue("@Password", txtpass.Text);
                    int result = (int)cmd.ExecuteScalar();
                    if (result > 0)
                    {
                        frmmainmdi mdi = new frmmainmdi();
                        a = "Yes";
                        mdi.A = "Yes";
                        mdi.Show();

                        this.Visible = false;
                    }
                    else
                        MessageBox.Show("User Not Found!");
                }

            }


        }

-KR

Posted 20-Mar-14 10:09am

Krunal Rohit

Comments

abdul manan 7 20-Mar-14 16:22pm

yes my main form is login form but when i click logout from menu string and again log in it open multiple mdi one already open second again open by login function

abdul manan 7 20-Mar-14 16:31pm

Second when i close all mdi the hide one still open
is there any way to close hide forms

Sergey Alexandrovich Kryukov 20-Mar-14 16:34pm

This is quite possible, but how?
What happens if the user clicks close button or hits Alt+F4? Don't you think you have to provide a solution for that? Otherwise, your advice won't work...
—SA

Krunal Rohit 20-Mar-14 16:36pm

same goes for the Form_Closing() as well...

-KR

Sergey Alexandrovich Kryukov 20-Mar-14 16:41pm

The mere mention of the name "Form_Closing" does not tell anything. There is not an event, "Form_Closing", right? :-)
—SA

Krunal Rohit 20-Mar-14 16:42pm

http://msdn.microsoft.com/en-us/library/system.windows.forms.form.closing(v=vs.110).aspx

-KR

abdul manan 7 20-Mar-14 16:39pm

Sir SA waiting for you came at very right time
would you please check my question and give me a solution

Sergey Alexandrovich Kryukov 20-Mar-14 16:42pm

I will. But wait a minute... Are you using MDI?
—SA

abdul manan 7 20-Mar-14 16:46pm

yes this is last time i am using mdi
after you send me that link last time
i will never use again

Sergey Alexandrovich Kryukov 20-Mar-14 16:52pm

Why are you using it now? I suggest you won't. If you do, it makes no sense to use more than one parent windows, so your problem would not exist.
So, I need to understand what forms do you want to have. Why not having everything on one form? What you have for forms not could be TabPages, Panels, whatever...
—SA

abdul manan 7 20-Mar-14 16:56pm

yah it's not good but now i cannot Go back my application is closer to finish...

abdul manan 7 20-Mar-14 17:03pm

i have the mdi to stay open when login close after entering correct data
and my start up(mainform) form is frmlogin.
Second problem is when i click logout and again login then another mdi open previous doesn't closed or if u close it through login function then everything disappear .

Sergey Alexandrovich Kryukov 20-Mar-14 17:08pm

I answered, but listen for a good advice: don't use MDI...
—SA