Appropriate point to attach NodeChanged event, XAML - wpf

I've got a WPF usercontrol in a winforms application form.
Basically, I want a generic eventhandler attached to my WPF TreeView to handle "Document.NodeChanged". As this particular event fires when the tree is populated, I attempted to do a late attachment, via my treeview control's Loaded event.
The code goes something like:
private void UpdateGrid()
{
myGridView.UpdateXML(entityId, runDate, rtbToggleFullView.ToggleState == Telerik.WinControls.Enumerations.ToggleState.Off, userName);
//Safely attach the event to fire when the treeview has finished loading.
myGridView.tvRatings.Loaded -= AttachNodeChangedEvent;
myGridView.tvRatings.Loaded += AttachNodeChangedEvent;
}
Then the "AttachNodeChangedEvent" method looks like this:
public void AttachNodeChangedEvent(object i, EventArgs a)
{
((XmlDataProvider)myGridView.dataProvider).Document.NodeChanged -= OnNodeChanged;
((XmlDataProvider)myGridView.dataProvider).Document.NodeChanged += OnNodeChanged;
}
With a simple OnNodeChanged method:
public void OnNodeChanged(object i, EventArgs a)
{
Dirty = true;
}
The idea being:-
UpdateGrid runs UpdatesXML on treeview
Attaches a "NodeChangeHandler attacher" to treeview.Loaded
(when treeview is loaded) treeview fires "NodeChangeHandler attacher" which then attaches "OnNodeChanged" to the Treeview's populated XmlDocumentProvider.
This appeared to work perfectly in Windows 7. In Windows XP, however, the AttachNodeChangedEvent routine fires, and experiences a NullReferenceException (presumably because the Document hasn't loaded yet?) crashing the app.
Commenting out the ...((XmlDataProvider)myGridView... lines fixes the crash, but obviously disables the functionality.
Can anyone suggest a better way of achieving the same, or shed some light on why this works for Windows 7, but not Windows XP? "e.g. Attach NodeChangedEvent after the initial population of the Treeview"
I can confirm that both use the appropriate .Net Framework 4 package and seem to have all other dependencies appropriately included.
Thanks!

Related

WinForm text box: MenuStrip keyboard shortcuts overriding OS-level copy/paste

Update: I've figured out the source of the issue, now trying to figure out the best fix
I've got a Form with a customized MenuStrip, with all sorts of bells and whistles. Of note here, is that many of my MenuStrip items have keyboard shortcuts - namely ones for Cut/Copy/Paste.
It appears that the presence of this MenuStrip is overriding (and therefore cancelling) the default Cut/Copy/Paste keyboard shortcut behaviors for my text boxes (and other controls).
All of them.
.
I can't really say I have a reason for the MenuStrip Cut/Copy/Paste options, besides the fact that I would expect to see them there. That's how Office type programs operate, and it's something the user (myself included) would expect.
I could remove the Cut/Copy/Paste options from the MenuStrip, but that would be admitting defeat! So how do I keep my overly engineered MenuStrip from forcing me to implement custom code for EVERY control that's Cut/Copy/Paste friendly?
.
** Original Post: **I've got a TextBox control in a toolbar which is to be used throughout my program. Imagine my surprise when native OS-level Copy/Paste events were not supported by default.
Sure, I could code something manually, but when I right-click on the control, Cut/Copy/Paste are already built in. How can I leverage this existing functionality?
I figure adding a KeyDown event with Ctrl+C, P, and X would be about the maximum I should have to code. For those events I just call a built-in method or something. That, or find a setting that enables native cut/copy/paste.
What am I overlooking/missing?
Testing it out native copy and paste does work on a TextBox control unless you are overridding the ContextMenu or ContextMenuStrip, in that case you will need to use the ClipBoard Class to implement it yourself.
In looking at it further this MSDN Forum article discusses sending the Commands to the Native Textbox Control using the SendMessage Method. This is implemented in a Custom TextBox which sounds like what you are doing.
Small excerpt see article for further implementation:
protected void itemCut_Click(object sender, EventArgs e)
{
SendMessage(this.Handle, TextBoxMessages.WM_CUT, 0, 0);
}
public static class TextBoxMessages
{
public const int EM_UNDO = 0x00C7;
public const int WM_CUT = 0x0300;
public const int WM_COPY = 0x0301;
public const int WM_PASTE = 0x0302;
}
Easy Solution: Use the SendKeys.Send() call within the Click event.
SendKeys.Send("^X");
I'm doing something a little more complicated, so here's the details:
I'm making several Forms, which all share some custom controls: MenuStrip, StatusStrip, and a few other custom controls. I've decided to have the Forms all inherit from the same base class, to allow common implementation of lots of stuff.
public partial class CommonFormBase : Form
{
private void Initialize()
{
//Bind click event for custom MenuStrip to events in the local Form
CommonMenuStrip.Edit_Cut.Click += new EventHandler(Edit_Cut_Click);
CommonMenuStrip.Edit_Copy.Click += new EventHandler(Edit_Copy_Click);
CommonMenuStrip.Edit_Paste.Click += new EventHandler(Edit_Paste_Click);
}
//Implement Click events for the MenuStrip by calling local methods
internal void Edit_Cut_Click(object sender, EventArgs e) { Cut(); }
internal void Edit_Copy_Click(object sender, EventArgs e) { Copy(); }
internal void Edit_Paste_Click(object sender, EventArgs e) { Paste(); }
//Generic implementation of common commands for the CommonFormBase
public virtual void Cut() { SendKeys.Send("^X"); }
public virtual void Copy() { SendKeys.Send("^C"); }
public virtual void Paste() { SendKeys.Send("^V"); }
}
I implemented the MenuStrip's click event at the Form level (not the MenuStrip level), but in that event I only call a generic method, which does all the code. In this example it's overkill, but I have other MenuStrip commands that will change in functionality for different child Forms, so I figured having them all work the same would be easier.
Anyway, this works almost perfectly! It seems to push the shortcut-key-activated MenuStrip_Click event to the underlying control (or maybe the Form?), which then implements default shortcut key events.
The only thing it does wrong is it only triggers ONCE when you do Ctrl + V + V + V... or hold Ctrl+V. Still, that's just a matter of the trigger not recognizing multiple events, not an issue with the solution itself.

Usercontrol with treeview selected event that refreshed another usercontrol not working

I'm relatively new to WPF programming and can't seem to get this working correctly. This is in my mind something rather simplistic that i would like to get working so I didn't try the MVVM framework and decided to keep it simple.
I have a usercontrol treeview with report paths. I have another usercontrol with a reportviewer. Selecting a report path in the treeview should refresh the reportviewer.
I can "call" the method from the treeview usercontrol for refreshing the reportviewer in the report usercontrol but nothing happens.
I was reading other posts and some seem to suggest a button event to a delegate that will allow the other usercontrol method to be executed. I'm not using a button event so I'm a bit puzzled.
I thought I could do something like this:
private void treeViewMenu_Selected(object sender, RoutedEventArgs e)
{
//Get the selected item
....
//Call the method of another user control
ReportUserControl ruc = new ReportUserControl();
ruc.RefreshReport();
}
Obviously that didn't work...I know that it shouldn't be too difficult but i am in a brain freeze moment and can't seem to get it working.
Any suggestions would be greatly appreciated.
Thanks!

wpf BackgroundWorker - Regarding updating UI

I use a browse for files dialog to allow a user to select multiple images. If a lot of images are selected, as expected it takes a bit. Below is an example of what I do with the selected images. I loop through the filepaths to images and create an instance of a user control, the user control has an Image control and a few other controls. I create the instance of this control then add it to a existing stackPanel created in the associating window xaml file. The example just below works fine, but I'm trying to understand BackGroundWorker better, I get the basics of how to set it up, with it's events, and pass back a value that could update a progress bar, but because my loop that takes up time below adds the usercontrol instance to an existing stackPanel, It won't work, being in a different thread. Is BackGroundWorker something that would work for an example like this? If so, what's the best way to update the ui (my stackpanel) that is outside the thread. I'm fairly new to wpf and have never used the BackGroundWorker besides testing having it just update progress with a int value, so I hope this question makes sense, if I'm way off target just let me know. Thanks for any thoughts.
Example of how I'm doing it now, which does work fine.
protected void myMethod(string[] fileNames) {
MyUserControl uc;
foreach (String imagePath in fileNames) {
uc = new MyUserControl();
uc.setImage(imagePath);
stackPanel.Children.Add(uc);
progressBar.Value = ++counter;
progressBar.Refresh();
}
}
below this class i have this so I can have the progressBar refresh:
public static class extensionRefresh {
private static Action EmptyDelegate = delegate() { };
public static void Refresh(this UIElement uiElement) {
uiElement.Dispatcher.Invoke(DispatcherPriority.Background, EmptyDelegate);
}
}
Check out this article on
Building more responsive apps with the Dispatcher
Now that you have a sense of how the Dispatcher works, you might be surprised to know that you will not find use for it in most cases. In Windows Forms 2.0, Microsoft introduced a class for non-UI thread handling to simplify the development model for user interface developers. This class is called the BackgroundWorker
In WPF, this model is extended with a DispatcherSynchronizationContext class. By using BackgroundWorker, the Dispatcher is being employed automatically to invoke cross-thread method calls. The good news is that since you are probably already familiar with this common pattern, you can continue using BackgroundWorker in your new WPF projects
Basically the approach is
BackgroundWorker _backgroundWorker = new BackgroundWorker();
// Set up the Background Worker Events
_backgroundWorker.DoWork += _backgroundWorker_DoWork;
_backgroundWorker.RunWorkerCompleted += _backgroundWorker_RunWorkerCompleted;
// Run the Background Worker
_backgroundWorker.RunWorkerAsync(5000);
// Worker Method
void _backgroundWorker_DoWork(object sender, DoWorkEventArgs e)
{
// Do something
}
// Completed Method
void _backgroundWorker_RunWorkerCompleted(object sender, RunWorkerCompletedEventArgs e)
{
// Doing UI stuff
if (e.Cancelled)
{
statusText.Text = "Cancelled";
}
else if (e.Error != null)
{
statusText.Text = "Exception Thrown";
}
else
{
statusText.Text = "Completed";
}
}
Using a BackgroundWorker alone won't solve your issue since elements created during the DoWork portion will still have originated from a non-UI thread. You must call Freeze on any objects you intend to use on another thread. However only certain UI objects will be freezable. You may have to load in the images as BitmapImages on the background thread, then create the rest of your user control on the UI thread. This may still accomplish your goals, since loading in the image is probably the most heavyweight operation.
Just remember to set BitmapImage.CacheOption to OnLoad, so it actually loads up the image when you create the object rather than waiting until it needs to be displayed.

WPF ComboBox DropDown part appears in the wrong place

I put several ComboBoxes on a XAML window. When I expand any of them, the DropDown part appears on the upper left corner of the screen.
I use Visual Studio 2008 C# Express. I don't remember this phenomenon when I used Visual Studio 2008 (Trial Version), though I use the same FrameWork (3.5).
It seems to be a bug.
Workaround:
Use Window.Show() instead with a custom logic to simulate the ShowDialog() behavior.
This appears to be a bug in WPF. In my case, I was trying to open a window in the Loaded event of another window. To get around this, I set a timer up to fire, then used a delegate to open the window (cannot open the window in a timer event because the calling thread that opens a window must be STA).
Edit - timer isn't necessary - didn't see the answer above just queue it on the dispatcher...
private delegate void DelegateOpenWindow();
private DelegateOpenWindow m_DelegateOpenWindow;
private Timer loginTimer = new Timer(200);
private void MainWindow1_Loaded(object sender, RoutedEventArgs e)
{
// create delegate used for asynchronous call
m_DelegateOpenWindow= new DelegateOpenWindow(this.OpenWindow);
// start a timer to fire off the open window.
loginTimer.Elapsed += loginTimer_Elapsed;
loginTimer.Enabled = true;
}
void loginTimer_Elapsed(object sender, ElapsedEventArgs e)
{
loginTimer.Enabled = false;
this.Dispatcher.BeginInvoke(m_DelegateOpenWindow);
}
void OpenWindow()
{
MyWindow w = new MyWindow();
w.Owner = this;
w.ShowDialog();
}
I started observing this (and other strange behavioral quirks) yesterday when I tried to "tweak" window sizes, shapes, colors, and invoke a log-on dialog from the Window.Loaded event handler. I had been doing this just fine in each of a dozen+ individual "MVVM" pattern apps. Yesterday, I decided to move this from each app's code behind into a consolidated code-behind base class, since the pre-processing had become common in all those apps. When I did, the drop-downs in two ComboBoxes in the log-in dialog suddenly appeared in the upper left corner of my screen. I seem to have "solved" it by using the following technique (your mileage may vary):
protected void WindowBaseLoadedHandler(object sender, RoutedEventArgs e)
{
...non-essential lines of code removed...
if (DataContext != null)
{
Dispatcher.BeginInvoke(DispatcherPriority.Normal, new Action(() =>
{
/*----------------------------------------------------------------------
* Do we have a View Model? If so, perform standard VM Initialization...
*---------------------------------------------------------------------*/
this.IsEnabled = false;
LoginDlg loginDlg = new LoginDlg();
loginDlg.ShowDialog();
if (!loginDlg.Success)
{
/*-----------------------------------
* Log on failed -- terminate app...
*----------------------------------*/
...termination logic removed...
}
this.IsEnabled = true;
}));
}
WindowBaseLoadedHandler is the Loaded event handler. LoginDlg is a WPF app with a dialog containing two ComboBoxes.
Recap: After I consolidated the code into the Loaded event handler of the base class the ComboBox's drop down lists appeared in the upper left corner of my screen. Once I wrapped the logic into the Dispatcher.BeginInvoke call, the appropriate ComboBox behavior returned with lists below the current item.
I suspect WPF needs the application to return from the Loaded event to complete the layout system's initialization. That doesn't fully explain why it worked before, but I'll have to queue up my desire to hunt that "why" down for some rainy day in the future and celebrate overcoming the latest obstacle for today.
In any event, I hope someone finds this of use.
I'm using the latest .Net 4.5 and WPF framework and I still have this problem. One thing I noticed is that it only happen when there's an attached debugger. When the debugger is not attached, everything works fine.
I had the same problem on Visual Studio 2019.
Using window.Show() can help but it can ruin your design.
The solution is to open the window asynchronously.
var yourDialog= new YourDialog();
yourDialog.Owner = this;
TaskCompletionSource<bool?> completion = new TaskCompletionSource<bool?>();
this.Dispatcher.BeginInvoke(new Action(() =>
completion.SetResult(yourDialog.ShowDialog())));
bool? result = await completion.Task;
You can also create a more elegant solution by making the extension method:
public static class AsyncWindowExtension
{
public static Task<bool?> ShowDialogAsync(this Window self)
{
if (self == null) throw new ArgumentNullException("self");
TaskCompletionSource<bool?> completion = new TaskCompletionSource<bool?>();
self.Dispatcher.BeginInvoke(new Action(() => completion.SetResult(self.ShowDialog())));
return completion.Task;
}
}
And you can use it like this:
await dlgReview.ShowDialogAsync();
It’s a bug in WPF (not the only one, I'm afraid). It happened when I opened another window in the Loaded Event, something like:
private void Window_Loaded(object sender, RoutedEventArgs e)
{
Window selectionWindow = new SelectionWindow();
bool? result = selectionWindow.ShowDialog();
if (result == true)
RecordChanged();
}
I already found a workabout.

Add a Load event for Winforms Control just as Form class

is there a way I can get a Load event for System.Windows.Forms.Control just like System.Windows.Forms.Form.Load?
I want to run some initialize code before the control first shown.
Also, it would be nice to be able to do the same for System.Windows.Forms.ToolStripStatusLabel which is not actually a Control, but works like one.
Ideally, I can do this:
control.OnLoad(() => { dosomething here; });
in which OnLoad is a extension method that would run the argument Action when the "control" "Loads".
Thanks!
Form.Load event is called by the OnLoad method which is called from the OnCreateControl method which belongs to the Control class. So for the form the calling sequence would be following:
OnCreateControl start
OnLoad start
Form Load event call
OnLoad finish
OnCreateControl finish
I guess you can override OnCreateControl for your component and add your optimization code there.
Hope this helps, Regards.
For a control you can override either OnControlCreated or OnHandleCreated. The latter one can fire multiple times if it is necessary to recreate the control window. Be sure to use it if your code affects the window itself. In other words, if you do anything that requires the Handle property.
Few suitable choices for a ToolStripItem derived control. I'd recommend overriding SetVisibleCore() or OnAvailableChanged() or the AvailableChanged event. They run when the Visible property of the ToolStripItem changes. Beware that it may fire multiple times, keep a bool field that tracks that your initialization code has already run.
Last but not least, be sure to only do any of this if your code actually requires the control to be created. The vast majority of init code can go in the constructor. You only need a Load event if your code depends on the actual Location and Size of the control. Which might be different from the designer value if the form rescales itself due to a different system font or video DPI setting on the target machine.
I needed a solution like this for a TabPage within a TabControl.The only thing I came up with was using the paint event handler. I added the event handler for Paint and in the very first line I remove the event handler and then do more initialization code. This only works if you do nothave any custom painting. Alternatively, if you do need to do custom painting you could add a flag to check for each time Paint Executes.
//Paint only runs once
private void tabPage1_Paint(object sender, PaintEventArgs e)
{
tabPage1.Paint -= tabPage1_Paint;
//Do initialization here
}
/////////////////////////////////////////////////////////////////////////////////
//Paint always runs
private bool IsFirstPaint = true;
private void tabPage1_Paint(object sender, PaintEventArgs e)
{
if(IsFirstPaint)
{
IsFirstPaint = false;
//Do initialization here
}
//Do custom painting here
}

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