SaveFileDialog button events in WPF - wpf

Question

I have a SaveFileDialog in my WPF Project.
If the SaveFileDialog is closed via the red 'x' in the corner, I want the dialog to close and the user to be returned to the main application.
However, if the SaveFileDialog is 'canceled', I want the entire application to close.
The only issue I am having is knowing if the user has pressed the red x or the cancel button. They both evaluate to false in the code below.
SaveFileDialog saveFileDialog = new SaveFileDialog();
saveFileDialog.Filter = "Text file (*.txt)|*.txt";
var dlg = saveFileDialog.ShowDialog();
if (dlg == true)
{
//When the user presses save
File.WriteAllLines(saveFileDialog.FileName, rowList);
ExitApp();
}
else if (dlg == false)
{
//This occurs when red x or cancel is pressed.
}
Is there any way to distinguish between the two in WPF?

Answer 1

The answer is short and simple:
"no"
See Microsoft documentation here

Answer 2

It is not so simple, but you can do it by using hooks and the SetWindowsHookEx method.
First of all we need a class for registering and unregistering our hook:
public class WinHooker
{
[DllImport("user32.dll", CharSet = CharSet.Auto, CallingConvention = CallingConvention.StdCall, SetLastError = true)]
private static extern int SetWindowsHookEx(int idHook, HookProc lpfn, IntPtr hMod, int dwThreadId);
[DllImport("user32.dll", CharSet = CharSet.Auto, CallingConvention = CallingConvention.StdCall)]
private static extern int CallNextHookEx(int idHook, int nCode, int wParam, IntPtr lParam);
[DllImport("user32.dll", CharSet = CharSet.Auto, CallingConvention = CallingConvention.StdCall, SetLastError = true)]
private static extern int UnhookWindowsHookEx(int idHook);
private delegate int HookProc(int nCode, int wParam, IntPtr lParam);
private HookProc hookDelegate;
private int hookHandle;
private bool wasClosedButtonPressed;
private static WinHooker instance;
private WinHooker()
{
}
public static WinHooker Instance
{
get
{
if (instance == null)
{
instance = new WinHooker();
}
return instance;
}
}
public bool WasClosedButtonPressed
{
get
{
return wasClosedButtonPressed;
}
}
public void Register()
{
wasClosedButtonPressed = false;
hookDelegate = this.HookProcHandler;
hookHandle = SetWindowsHookEx(5,
hookDelegate,
IntPtr.Zero,
AppDomain.GetCurrentThreadId());
}
public void Unregister()
{
UnhookWindowsHookEx(hookHandle);
hookHandle = 0;
hookDelegate = null;
}
private int HookProcHandler(int nCode, int wParam, IntPtr lParam)
{
if (nCode >= 0)
{
if (nCode == 8 && wParam == 0xF060)
{
wasClosedButtonPressed = true;
}
}
return CallNextHookEx(hookHandle, nCode, wParam, lParam);
}
}
As you can see I used 5 as the first parameter for the SetWindowsHookEx, since it correspond to the WH_CBT value (refer to the SetWindowsHookEx page). Moreover the values in the method HookProcHandler (i.e. nCode == 8 && wParam == 0xF060) can be retrived from here.
Now let's use our class in the code:
SaveFileDialog saveFileDialog = new SaveFileDialog();
WinHooker.Instance.Register();
saveFileDialog.ShowDialog();
WinHooker.Instance.Unregister();
if (WinHooker.Instance.WasClosedButtonPressed)
{
MessageBox.Show("Oh my God! What have you done??");
}
As you can understand WasClosedButtonPressed is set to true just if the user closes the dialog by clicking on the red 'x' in the corner. Otherwise it is false.
I hope it can help you.