Question

I have created 2 forms in VS Studio 2008 Express Edition and declare them with public static in main program.cs file

I just want to switch between the two forms with ShowDialog and Close but when trying to close the second form and open the first form again with showdialog it says I cannot use showDialog when the form is already visible, whereas it isn’t true since I closed it before to show the second form.

It asked me to set the form visible property to false before using showdialog, so I did it

    internal static void CloseSecondForm(FirstForm FirstForm)
    {
        FirstForm .Close();
        SecondForm.Visible = false;
        SecondForm.ShowDialog();
    }

But then it says I cannot use ShowDialog because the form is already shown in Dialog Mode and that I must close it. So I did what it asked

    internal static void CloseSecondForm(FirstForm FirstForm)
    {
        FirstForm .Close();
        SecondForm.Visible = false;
        SecondForm.Close();
        SecondForm.ShowDialog();
    }

But it still pretends that the form is already opened with ShowDialog !

Is this a Bug in my prog or in Winform ?

Update: this is the whole code I posted in 5th answer (I want to use showdialog and not show because I may have a 3rd form in Background that I don’t want the user to access):

  [STAThread]
  static void Main()
  {
      Application.EnableVisualStyles();
      Application.SetCompatibleTextRenderingDefault(false);
      Form1 = new Form1();
      Form2 = new Form2();
      Form1.ShowDialog();
      Application.Run();

  }

  // called from Form1 BUTTON
  internal static void ShowForm2(Form1 Form1)
  {
      Form1.Hide();
      Form2.ShowDialog();
  }

  // called from Form2 BUTTON
  internal static void ShowForm1(Form2 Form2)
  {
      Form2.Hide();
      Form1.ShowDialog();
  }

---

I tried with Hide as suggested but it doesn’t work either. This is the whole program, what I want to do is very simple: I have two forms initially created in program with one button on each form to close self and open the other. I put all the logic in program.cs below:

  using System;
  using System.Windows.Forms;

  namespace twoforms
  {
      static class Program
      {
          /// <summary>
          /// The main entry point for the application.
          /// </summary>
          /// 
          public static Form1 Form1;
          public static Form2 Form2;

          [STAThread]
          static void Main()
          {
              Application.EnableVisualStyles();
              Application.SetCompatibleTextRenderingDefault(false);
              Form1 = new Form1();
              Form2 = new Form2();
              Form1.ShowDialog();
              Application.Run();

          }

          // called from Form1 BUTTON
          internal static void ShowForm2(Form1 Form1)
          {
              Form1.Hide();
              Form2.ShowDialog();
          }

          // called from Form2 BUTTON
          internal static void ShowForm1(Form2 Form2)
          {
              Form2.Hide();
              Form1.ShowDialog();
          }
      }
  }

Answer 1

This is from MSDN:

When a form is displayed as a modal
dialog box, clicking the Close button
(the button with an X at the
upper-right corner of the form) causes
the form to be hidden and the
DialogResult property to be set to
DialogResult.Cancel. Unlike modeless
forms, the Close method is not called
by the .NET Framework when the user
clicks the close form button of a
dialog box or sets the value of the
DialogResult property. Instead the
form is hidden and can be shown again
without creating a new instance of the
dialog box. Because a form displayed
as a dialog box is not closed, you
must call the Dispose method of the
form when the form is no longer needed
by your application.

So once you show a form using ShowDialog and you now want to close it, just let it return DialogResult.Cancel
This will hide (it will still be in memory) your first form. Now you can call ShowDialog on your second form. Again, if you want to switch to first form then let the second form return DialogResult.Cancel and now just call ShowDialog on first form.