How to switch between forms without creating new instance of forms?

Question

in my application i have four forms form1 form2 form3 form4 .and each form have two buttons i.e next and previous buttons to switch between forms .and my question is how can i Switch between forms without creating new instance of forms? below is my code

In Form1:

    public Form1()
   {
       InitializeComponents();
   }

    private void Next_Click(object sender, EventArgs e)
    {
      this.Hide()
       Form2  form2 = new Form2();
       form2.Show();
    }      

In Form2:

    public Form2()
   {
       InitializeComponents();
   }
    private void Previous_Click(object sender, EventArgs e)
    {
       this.Hide();
       Form1 form1 = new Form1();
       form1.Show();
    }

    private void Next_Click(object sender, EventArgs e)
    {
         this.Hide();
       Form3 form3 = new Form3();
       form3.Show();
    }      

In Form3:

    public Form3()
   {
       InitializeComponents();
   }
    private void Previous_Click(object sender, EventArgs e)
    {
        this.Hide();
       Form2 form2 = new Form2();
       form2.Show();
    }

    private void Next_Click(object sender, EventArgs e)
    {
         this.Hide();
       Form4 form4 = new Form4();
       form4.Show();
    }      

In Form4:

    public Form4()
   {
       InitializeComponents();
   }
    private void Previous_Click(object sender, EventArgs e)
    {
         this.Hide();
       Form3 form3 = new Form3();
       form3.Show();
    }

In Main:

static void Main()
    {
        Application.EnableVisualStyles();
        Application.SetCompatibleTextRenderingDefault(false);

        Application.Run(new Form1());


    }

In above code i am creating new instances of forms every time..,How can i Avoid this and How can i Switch between forms without creating new instances of forms.... please help me

Answer 1

Since you are accessing your forms sequentially just make sure that you use the Show Method that assigns the owner to the created Form and assign it to a class level variable after you create it. Something like this should work for you.

Form1

public partial class Form1 : Form
{
    Form2 frm2;
    public Form1()
    {
        InitializeComponent();
    }

    private void button1_Click(object sender, EventArgs e)
    {
        if (frm2 == null)
        {
            frm2 = new Form2();   //Create form if not created
            frm2.FormClosed += frm2_FormClosed;  //Add eventhandler to cleanup after form closes
         }

        frm2.Show(this);  //Show Form assigning this form as the forms owner
        Hide();
    }

    void frm2_FormClosed(object sender, FormClosedEventArgs e)
    {
        frm2 = null;  //If form is closed make sure reference is set to null
        Show();
    }
}

Form2

public partial class Form2 : Form
{
    Form3 frm3;
    public Form2()
    {
        InitializeComponent();
    }

    private void button1_Click(object sender, EventArgs e)
    {
        Owner.Show();  //Show the previous form
        Hide();

    }

    private void button2_Click(object sender, EventArgs e)
    {
        if (frm3 == null)
        {
            frm3 = new Form3();
            frm3.FormClosed += frm3_FormClosed;
        }

        frm3.Show(this);
        Hide();
    }

    void frm3_FormClosed(object sender, FormClosedEventArgs e)
    {
        frm3 = null;
        Show();
    }
}

Form3

public partial class Form3 : Form
{
    public Form3()
    {
        InitializeComponent();
    }

    private void button1_Click(object sender, EventArgs e)
    {
        Owner.Show();
        Hide();
    }
}

Answer 2

May be a easy solution. You can make a class that contains static object of all forms that you need. So you will be able to access all these forms from any forms of your choice and the good thing is they are initialized once.

public class formList
{
      private static Form1 _form1 = new Form1();
      public static Form1 form1 { get {return _form1;}
      .................
      ............
}

Answer 3

Try This:

Form1 myForm =(Form1) Application.OpenForms["Form1"];
myForm.Show();