How to close Opened Form and open new Form on button click

Question

I have two Winforms open at present.Out of the two one is Login form.Now as per my requirement ,if the user entered right credentials then these two opened forms needs to be closed and new form should be opened. Means I have to close opened winforms and open new Winform on button click event of Login form. Here i am not knowing exactly which windows are open because login form window is coming from menu button click event which is present on every form Please help me.Thanks in advance..

Answer 1

You can iterate over the Application.OpenForms collection and close that you need.

Answer 2

Try this:

foreach (Form f in Application.OpenForms)
{
    f.Close();
}

OR using for loop:

for (int i = Application.OpenForms.Count - 1; i >= 0; i--)
{
     Application.OpenForms[i].Close();
}

OR create a list of forms:

List<Form> openForms = new List<Form>();
foreach (Form f in Application.OpenForms)
    openForms.Add(f);
foreach (Form f in openForms)
{
   f.Close();
}

As per you requirement, close all other forms except login form and then show that form.

foreach (Form f in Application.OpenForms)
    {
        if(f.Name!="frmLogin")   //Closing all other
            f.Close();           //forms
    }

Now activate the login form.

frmLogin.Show();
frmLogin.Focus();

Application.OpenForms gets a collection of open forms owned by the application. Read more about Application.OpenForms.

Answer 3

you can't use foreach to close the forms as suggested in earlier replies. This is because foreach cannot be used to alter the enumerated forms list (when you Close() them, you will get a run-time error). Even if you use a for loop, you'll have to check that the main form is also not closed by mistake...

for(int i=0; i< Application.OpenForms.Count; i++)
{
    Form f = Application.OpenForms[i];
    if(f != this)
        f.Close();
}

Instead, you can try out the below logic. Where are these two forms getting loaded from? is it from a main form? I am assuming that both are being displayed using Form.Show() method.

In the login form login button handler, I'd accept a reference to the main form. when validation succeeds, I'd call a function LoginSuccessful() in the parent form, which would iterate through the open forms and close them.

public partial class FormMain : Form
{
    LoginForm loginForm;
    OtherForm otherForm;

    public FormMain()
    {
        InitializeComponent();
    }

    private void Form1_Load(object sender, EventArgs e)
    {
        loginForm = new LoginForm(this);
        otherForm = new OtherForm();

        loginForm.Show();
        otherForm.Show();
    }

    public void LoginSuccessful()
    {
        loginForm.Close();
        otherForm.Close();  
        OtherForm thirdForm = new OtherForm();
        thirdForm.Show();
    }
}

LoginForm code as below:

public partial class LoginForm : Form
{
    FormMain parent;
    bool bLoginSuccessful = false;

    public LoginForm(FormMain parent)
    {
        InitializeComponent();
        this.parent = parent;
    }

    private void button1_Click(object sender, EventArgs e)
    {
        bLoginSuccessful = true;
        Thread.Sleep(5000);
        if (bLoginSuccessful == true)
            parent.LoginSuccessful();
    }
}

This should help you in solving your problem... Granted, it isn't the best way... It all depends upon your approach. If you are more detailed in your requirement, I can probably think out a better way.

Answer 4

In your login form, make default constructor private and add a new constructor and a private member like this:

private Form _callerform;

private LoginForm()
        {
            InitializeComponent();
        }

public LoginForm(Form caller)
        {
            InitializeComponent();
        }

Now, in the click event of button on LoginForm, try something like this:

        Form SomeOtherForm = new Form();
        SomeOtherForm.Show();
        // Hide login and caller form
        Hide();
        _callerForm.Hide();

Now, you have hidden a couple of forms and opened a new one. When the user closes the application, you need to close other forms too. So,

    void Application_ApplicationExit(object sender, EventArgs e)
    {
        foreach (Form form in Application.OpenForms)
        {
            form.Close();
        }
    }