/// <summary>
/// Unregisters a form for receiving a callback notification when another instance was started.
/// </summary>
/// <param name="form">The form to register.</param>
/// <exception cref="ArgumentNullException">Thrown when the specified form is null.</exception>
/// <exception cref="ArgumentException">Thrown when the form is not registered.</exception>
public void UnregisterForm(Form form)
{
if (form == null)
{
throw new ArgumentNullException(nameof(form));
}
if (!_forms.Contains(form))
{
return;
}
// If the form being unregistered is our listener form, release the filter.
if (_messageFilter.Handle == form.Handle)
{
_messageFilter.ReleaseHandle();
}
form.Disposed -= Form_Disposed;
_forms.Remove(form);
// If the filter was just released, reassign it to another form.
if (_messageFilter.Handle != IntPtr.Zero || _forms.Count <= 0)
{
return;
}
foreach (var other in _forms)
{
Win32Exception lastEx;
try
{
_messageFilter.AssignHandle(other.Handle);
break;
}
catch (Win32Exception ex) { lastEx = ex; }
if (_messageFilter.Handle == IntPtr.Zero)
{
throw new InvalidOperationException("An unexpected error occurred while attempting assign message filter.", lastEx);
}
}
}
/// <summary>
/// Performs application-defined tasks associated with freeing, releasing, or resetting unmanaged resources.
/// </summary>
/// <param name="disposing">True if disposing.</param>
private void Dispose(bool disposing)
{
if (_disposed)
{
return;
}
if (disposing)
{
_messageFilter?.ReleaseHandle();
_messageFilter = null;
}
if (_mutexOwned)
{
_mutex.ReleaseMutex();
}
_mutex.Dispose();
_disposed = true;
}