C#

Form2 form2;
private void button1_Click(object sender, EventArgs e)
{
  if(form2 == null || form2.IsDisposed)
    form2 = new Form2();
  form2.Show();
}

musefan wrote:

if(form2.IsDisposed || form2 == null)

Luc Pattyn wrote:

I never did those reverse compares, not in all my years programming in C and other languages that might benefit from it.

Luc Pattyn wrote:

Never has been a problem. We tend to use tools at their most critical setting; and most of the C compilers we used regularly accurately emitted warnings on anything that could be unintentional, such as missing equal signs and empty loop blocks.

int n = 1;
if( n = 2)
    cout << "now it's two" << endl;

Form2 form2 = null;

case "Exit":
Application.Exit();
break;//well you would not actually need this

Application.Run(new Form1());

public static bool ShowLogin = true;

while(ShowLogin)
{
  Form2 loginForm = new Form2();
  if(loginForm.ShowDialog() == DialogResult.OK)//login has passed
    Application.Run(new Form1());
  else
    ShowLogin = false;//or break; or return;
}

this.DialogResult = DialogResult.OK;
this.Close();

this.DialogResult = DialogResult.Cancel;
this.Close();

case "LOGOFF":
this.Close();
break;
case "EXIT":
Program.ShowLogin = false;
this.Close();
break;