C# Open a New Form Then Close the Current Form

Closing current form and open another form

DetailForm df = new DetailForm();

df.Show();

this.Close();

But be careful, if you close the main form the application will be closed.

EDITED

To run this if the first form is the main form you need do more. Try something like this:

Change your Program.cs file to this:

public static class Program
{
    public static bool OpenDetailFormOnClose { get; set; }

    /// <summary>
    /// The main entry point for the application.
    /// </summary>
    [STAThread]
    static void Main()
    {
        Application.EnableVisualStyles();
        Application.SetCompatibleTextRenderingDefault(false);

        OpenDetailFormOnClose = false;

        Application.Run(new MainForm());

        if (OpenDetailFormOnClose)
        {
            Application.Run(new DetailForm());
        }
    }
}

And in the main form, close it with this:

private void Foo(object sender, EventArgs e)
{
    Program.OpenDetailFormOnClose = true;

    this.Close();
}

If you set OpenDetailFormOnClose with true after the close of the main form, the DetailForm will be call.

Close Current form open new one of that form closed

Declare the Variable for the Form2 as class variable outside of the scope of the btnSave_Click method. This way you will be able to access it again when the button is clicked a second time.

Form frm2 = new Form2();

private void btnSave_Click(object sender, EventArgs e)
{

    if(frm.Visible)  // check whether the form is already showing
    {
        frm.Close();  // if yes close it first
    }

    frm2 = new Form2(); // then make a new form and show it
    frm2.Show();

How to Close Current Form and Return to Main Form

I think you can simple pass your MainForm Object to FormA then FormA to FormB then on click of button you should simple show your FormA object.

As per your code, you are here showing new MainForm object which is not you have created first time as you are creating new object in buttonGoBack_Click event.

You should need to make change in FormA

public MainForm mainForm {get;set;}

public  FormA(MainForm mainForm)
{
  this.mainForm= mainForm;

}

You should need to make change in FormB

public MainForm mainForm {get;set;}

public  FormB(MainForm mainForm)
{
  this.mainForm= mainForm;

}


        private void buttonOpenFormA_Click(object sender, EventArgs e)
        {
            formA displayformA = new formA(this);
            displayformA.Show();

            this.Hide();
        }

             private void buttonOpenFormB_Click(object sender, EventArgs e)
            {
                formB displayformB = new formB(this.mainForm);
                displayformB.Show();

                this.Hide();
            }

        private void buttonGoBack_Click(object sender, EventArgs e)
        {
            (this.mainform as MainForm).Show();
             this.Close();
        }

How to hide/close Current Form and opens a new form using a button inside the UserControl ? C#

This code creates a new instance and closes it hidden. However, this doesn't affect the main window as they are not related.

MainForm mainform = new MainForm();
mainform.Hide();
mainform.Close();

this.ParentForm.Hide(); can complete the operation of hiding the main window.

usercontrol：

code：

using System;
using System.Windows.Forms;

namespace WindowsFormsControlLibrary1
{
    public partial class UserControl1 : UserControl
    {
        public UserControl1()
        {
            InitializeComponent();
        }

        private void button1_Click(object sender, EventArgs e)
        {
            if (this.textBox1.Text == "admin" && this.textBox2.Text == "admin")
            {
                MessageBox.Show("Login Successfully");
                UserForm dashboard = new UserForm();
                this.ParentForm.Hide();
                dashboard.ShowDialog();
                this.ParentForm.Close();
            }
            else
            {
                MessageBox.Show("Login Error");
            }
        }
    }
}

Mainform:

Output:

C# Close a form in panel and open a new form in the same panel

You can not create an instance of the MainForm class and call its method, but you must use the existing instance. To use open forms, you must find the form with the name of the program.

Change Login_Click to :

private void Login_Click(object sender, System.EventArgs e)
{
    f1.ShowDialog();

    this.Hide();
    LoginForm loginForm = new LoginForm()
    {
        Dock = DockStyle.Fill,
        TopLevel = false,
        TopMost = true
    };
    MainForm mainForm = Application.OpenForms.OfType<MainForm>().Where(x => x.Name == "mainFormName").FirstOrDefault();
    mainForm.showForm(loginForm);
}

In the line Where(x => x.Name == "mainFormName") put the form name instead of mainFormName.

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