Question

Code for creating the CustomMessageBox:

CustomMessageBox is a property, and not a reference to the C# Class in the Toolkit.

CustomMessageBox.Dismissed += (dismissSender, dismissedEvent) =>
{
    switch (dismissedEvent.Result)
    {
        case CustomMessageBoxResult.LeftButton:
            PlaceCall(clickedFavorite.Name, clickedFavorite.PhoneNo);
            break;
        case CustomMessageBoxResult.RightButton:
            HERE ---> SendText(clickedFavorite.PhoneNo);
            break;
    }
};

Code for SendText() method:

private void SendText(String phoneNo)
{
    var smsTask = new SmsComposeTask
                      {
                          To = phoneNo
                      };

    smsTask.Show();
}

Thing is when the SmsComposeTask has started, the Phone navigates to the SMS application, which is correct.

If the user then decides to go back, with the Hardware Back Button, the SMS application closes and the phone shows my app again – but immediately closes, caused by a NullPointerException:

   at Microsoft.Phone.Controls.CustomMessageBox.ClosePopup(Boolean restoreOriginalValues)
   at Microsoft.Phone.Controls.CustomMessageBox.<>c__DisplayClass4.<Dismiss>b__1(Object s, EventArgs e)
   at Microsoft.Phone.Controls.Transition.OnCompleted(Object sender, EventArgs e)
   at MS.Internal.CoreInvokeHandler.InvokeEventHandler(Int32 typeIndex, Delegate handlerDelegate, Object sender, Object args)
   at MS.Internal.JoltHelper.FireEvent(IntPtr unmanagedObj, IntPtr unmanagedObjArgs, Int32 argsTypeIndex, Int32 actualArgsTypeIndex, String eventName)

I have also tried to override the OnBackKeyPress event, like this:

protected override void OnBackKeyPress(System.ComponentModel.CancelEventArgs e)
{
    if (CustomMessageBox != null && CustomMessageBox.IsEnabled)
    {
        e.Cancel = true;
    }
    else
    {
        base.OnBackKeyPress(e);
    }
}

Does anyone know what to do?

Answer 1

I have found a solution to my own problem. Instead of using the faulty CustomMessageBox, I found Coding4Fun Windows Phone Toolkit which provides a by far, more stable message box called MessagePrompt – here’s how to use it.

Create buttons

var smsButton = new Button { Content = "SMS" };
smsButton.Click += (o, args) =>
{
    // do something
};

var buttonList = new List<Button>
{
    smsButton
};

Create the actual message prompt

var msgPrompt = new MessagePrompt
{
    Title = "Message Prompt Title",
    Body = new TextBlock { Text = "Text for the Body", FontSize = 25, TextWrapping = TextWrapping.Wrap },
    ActionPopUpButtons = buttonList
};

Show it

msgPrompt.Show()

No bullocks

The good thing, which I have experienced with this MessagePrompt is that you are not bound to two static Left and Right buttons like with CustomMessageBox.

And if you want, you can set the Body property to a whole new XAML page, which makes this control flexible.

Reference: Coding4Fun WP7 Message Prompt in depth