When would ShowDialog() return null?

Posted by Joe White on Stack Overflow See other posts from Stack Overflow or by Joe White
Published on 2009-06-13T06:16:39Z Indexed on 2010/03/18 4:41 UTC
Read the original article Hit count: 503

Filed under:

wpf

|

showdialog

|

null

WPF's Window.ShowDialog method returns a nullable boolean. So does CommonDialog.ShowDialog.

Now, I understand cases where these would return false (user clicked Cancel or pressed Esc), and when they would return true (code sets Window.DialogResult to true, probably in response to OK being clicked). But null?

My first thought is that clicking the title bar's Close button might return null. But the docs state (and I confirmed by testing) that the title-bar Close button is treated as a Cancel.

So when would Window.ShowDialog or CommonDialog.ShowDialog ever return null?

© Stack Overflow or respective owner

Related posts about wpf

C#/WPF - RoutedEvent in WPF class that isn't a UIElement

as seen on Stack Overflow - Search for 'Stack Overflow'
I have a class that needs to notify that something significant has occured. The class is in a WPF-project, even though this specific class, is lookless (and doesn't inherit from UIElement, neither directly or indirectly). Normally, I just register a RoutedEvent to get this functionality but as this… >>> More
How to pass value from wpf form to wpf user control

as seen on Stack Overflow - Search for 'Stack Overflow'
Hai am having a WPF user control in my WPF Form, when i click my button in my form , i just want to pass some value to the textbox which is in the usercontrol, tell me how to do this. >>> More
WPF opening up exe program within WPF window

as seen on Stack Overflow - Search for 'Stack Overflow'
Not sure if this is possible but is there a way to open up another program like notepad within the container of a WPF window? similiar to that of being able to open a web page using the webbrowser control? Basically I would like to open notepad or other exe but keep it constrained within the WPF… >>> More
Silverlight Commands Hacks: Passing EventArgs as CommandParameter to DelegateCommand triggered by Ev

as seen on ASP.net Weblogs - Search for 'ASP.net Weblogs'
Today I've tried to find a way how to pass EventArgs as CommandParameter to DelegateCommand triggered by EventTrigger. By reverse engineering of default InvokeCommandAction I find that blend team just ignores event args.To resolve this issue I have created my own action for triggering delegate commands… >>> More
Building applications with WPF, MVVM and Prism(aka CAG)

as seen on ASP.net Weblogs - Search for 'ASP.net Weblogs'
In this article I am going to walk through an application using WPF and Prism (aka composite application guidance, CAG) which simulates engaging a taxi (cab). The rules are simple, the app would have3 screens A login screen to authenticate the user An information screen. A screen… >>> More

Related posts about showdialog

When would ShowDialog() return null?

as seen on Stack Overflow - Search for 'Stack Overflow'
WPF's Window.ShowDialog method returns a nullable boolean. So does CommonDialog.ShowDialog. Now, I understand cases where these would return false (user clicked Cancel or pressed Esc), and when they would return true (code sets Window.DialogResult to true, probably in response to OK being clicked)… >>> More
WPF Dispatcher.UnhandledException within a ShowDialog call.

as seen on Stack Overflow - Search for 'Stack Overflow'
It appears that ShowDialog() invokes the Dispatcher message handling loop within. Thus, you have a stack that looks something like: Outer-most Dispatcher message loop ... x.ShowDialog() Inner Dispatcher message loop ... I am using the Dispatcher.UnhandledException to catch exceptions not handled… >>> More
mybase.showdialog event fired without apparent reason

as seen on Stack Overflow - Search for 'Stack Overflow'
Hi, i'm new to vb .net and oop although i have learned the basics. I'm working in VB and .NET CF 3.5 and i'm trying to pass and received a value with showdialog. The issue here is when i'm done with a procedure in Load, for some reason MyBase.Showdialog (line 3) gives an error of "NullReferenceException… >>> More
Show form that showDialog from mainForm won't block it, but closing mainForm will close it

as seen on Stack Overflow - Search for 'Stack Overflow'
how yo show a form which needs to run synchronously. I tried running application.run from a queueworker of a threadpool- but I had some invalid handles sometime. tried using a regular thread but then when main form closes it doesn't close this- and I don't really like the idea of killing the thread… >>> More
ShowDialog won't run

as seen on Stack Overflow - Search for 'Stack Overflow'
I've come across a situation where I try to run a simple line of code in a method Dim res As DialogResult = frmOptions.ShowDialog() but nothing happens. The dialog box will not appear. If I run this method from another location in the code it executes fine (i.e. displays the form in dialog mode… >>> More