C#

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;

string ConfigFile = @"c:\MyConfig.cfg";

// Save 
int a = 10;

string b = "hi";

DataTable c = new DataTable();

Stream StreamFile = File.Open(ConfigFile, FileMode.CreateNew);
BinaryFormatter binformat = new BinaryFormatter();
binformat.Serialize(StreamFile, a);
binformat.Serialize(StreamFile, b);
binformat.Serialize(StreamFile, c);
StreamFile.Close();



// Read 
 Stream StreamFile = File.Open(ConfigFile, FileMode.Open);
 BinaryFormatter binformat = new BinaryFormatter();

int a1 = (int)binformat.Deserialize(StreamFile);
string b1 = (string)binformat.Deserialize(StreamFile);
DataTable c1 = (DataTable)binformat.Deserialize(StreamFile);
StreamFile.Close();