c# - 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();
    }
}