We Keep Coding

WPF Frame.Navigate triggering multiple events

I'm a fairly new to WPF and C#.
I have a frame component on my main window and 4 buttons next to it that navigate to different views in the frame. Within one the the views there is a DataGrid that has a SelectionChanged event which makes an SQL call to a database that fetches records, whose data is then used to populate a list of custom objects (these relate to the selected item on the DataGrid).
Anyways, the problem I have is that from time to time multiple calls (2 or 3) to the SelectionChanged event are being triggered at the same time for a single selection change (mouseclick) on the DataGrid.
The navigation button click events on the main window all look like this:
private void btn_MyDesk_Click(object sender, RoutedEventArgs e)
{
MainFrame.Navigate(new Uri("/Views/MyDeskView.xaml", UriKind.Relative));
}
private void btn_AllOrders_Click(object sender, RoutedEventArgs e)
{
MainFrame.Navigate(new Uri("/Views/AllOrdersView.xaml", UriKind.Relative));
}
After some experiementation, I've found that the bug only happens after changing views away from the view with the DataGrid, and then changing back to it (but not always). When the bug appears the number of calls generally corresponds to the number of times I had switched views. Furthermore, the bug will simply vanish if leave the program alone for a minute or two. This makes me suspect that there multiple instances of the DataGrid view lingering like ghosts in memory and duplicating event calls until they are cleaned up by a garbage collector.
Should I be cleaning something up each time I switch views, or am I looking in the wrong place?
Thank you in advance for any help.
Edit: In answer to #Peter Moore
I subscribe to the event in the DataGrid declaration within the views XAML: SelectionChanged="dtg_MyDeskOrderGrid_SelectionChanged"
Edit: This is the sequence that happens on a selection change in the data grid. It includes several UI changes while the SQL records for the new selection are retrieved and displayed on a second DataGrid (dtg_MyDeskOrderItems). While the SQL call is being made, the relevant controls are disbaled and a semi-transparent panel (bdr_DGLoadingPanel) is moved on screen to cover them and display a loading animation. When the work is done, the work area is re-enabled and the loading panel moved off screen. Focus is also returned to the main "order" Datagrid.
dtg_MyDeskOrderGrid: This is the main DataGrid showing all "Orders"
dtg_MyDeskOrderItems: This is a secondary DataGrid that is updated to show all "Items" in the selected order.
private void dtg_MyDeskOrderGrid_SelectionChanged(object sender, SelectionChangedEventArgs e)
{
CurrSelectedOrder = (Order_class)dtg_MyDeskOrderGrid.SelectedItem;
if (CurrSelectedOrder.ItemList == null)
{
if (NowWorking == false)
{
NowWorking = true;
bdr_DGLoadingPanel.Margin = new Thickness(2);
dtg_MyDeskOrderGrid.IsEnabled = false;
bdr_FilterPanel.IsEnabled = false;
bdr_DGLoadingPanel.Focus();
img_LoadingCircle.RenderTransform = rt;
img_LoadingCircle.RenderTransformOrigin = new Point(0.5, 0.5);
da.RepeatBehavior = RepeatBehavior.Forever;
rt.BeginAnimation(RotateTransform.AngleProperty, da);
bdr_DGLoadingPanel.UpdateLayout();
worker.RunWorkerAsync();
}
}
else
{
dtg_MyDeskOrderItems.ItemsSource = null;
dtg_MyDeskOrderItems.ItemsSource = CurrSelectedOrder.ItemList;
dtg_MyDeskOrderItems.Items.Refresh();
}
}
private void worker_DoWork(object? sender, DoWorkEventArgs e)
{
DatabaseConnection DBConn9 = new DatabaseConnection();
DBConn9.FillOrderItems(CurrSelectedOrder);
}
private void worker_RunWorkerCompleted(object? sender, RunWorkerCompletedEventArgs e)
{
this.Dispatcher.Invoke(() =>
{
dtg_MyDeskOrderItems.ItemsSource = null;
dtg_MyDeskOrderItems.ItemsSource = CurrSelectedOrder.ItemList;
dtg_MyDeskOrderItems.Items.Refresh();
bdr_DGLoadingPanel.Margin = new Thickness(1000, 2, 2, 2);
rt.BeginAnimation(RotateTransform.AngleProperty, null);
dtg_MyDeskOrderGrid.IsEnabled = true;
bdr_FilterPanel.IsEnabled = true;
// The following work-around and accompanying GetDataGridCell function were used to give keyboard focus back to the datagrid to make navigation with arrow keys work again.
// It appears keyboard focus is not returned to the Datagrid cells when using the Datagrid.focus() method.
Keyboard.Focus(GetDataGridCell(dtg_MyDeskOrderGrid.SelectedCells[0]));
NowWorking = false;
});
}
Edit...
Following the advice of the commentors, I was able to fix the bug by unsubscribing from the event in the Unloaded event for the view containing the DataGrid:
private void uct_MyDeskView_Unloaded(object sender, RoutedEventArgs e)
{
dtg_MyDeskOrderGrid.SelectionChanged -= dtg_MyDeskOrderGrid_SelectionChanged;
}
However, I was not able to reproduce the bug using a barebones testing project.
The UI in the original project is quite heavy, so I'm wondering if it's not the old view and events lingering in memory as this seems to fit the behavior of the bug & fix (Only occuring when I navigate away and back causing a new view to be created, multiple event triggers corresponding to the number of times I navigated away, and then finally the bug vanishing of its own accord after a moment or two).
I won't be settling on this as a final solution and instead will learn about ways I can reuse instances of my views (as suggested by Bionic) instead of recreating them. The reason for this is, if the SelectionChanged event is getting multiple triggers from old view instances, then it is likely other events will suffer from the same bug. This would be bad.
#BionicCode If you are still around, could you repost your initial comment as a solution so I can mark it answered?
Thank you to everyone for all the help and education. ^_^

Following the advice of the commentors, I was able to initially fix the bug by unsubscribing from the event in the Unloaded event for the view containing the DataGrid:
private void uct_MyDeskView_Unloaded(object sender, RoutedEventArgs e)
{
dtg_MyDeskOrderGrid.SelectionChanged -= dtg_MyDeskOrderGrid_SelectionChanged;
}
However as this solution only disconnected the one event and didn't solve the root problem of old views lingering in the background and firing events before being cleaned up, I finally went the following code that keeps only one instance of my view in memory and reuses it.
private MyDeskView? currMyDeskView = null;
private void btn_MyDesk_Click(object sender, RoutedEventArgs e)
{
if (currMyDeskView == null)
{
currMyDeskView = new MyDeskView();
}
MainFrame.Navigate(currMyDeskView);
}
Thank you to everyone who helped me get over this bug.

How can I add files to a listView from the Main Form using C#?

I have a software in C# that has a main form (meaning the form that opens when you start a software like almost every software has). However, the main form opens a form called ProjectFiles . I would like to know if it is possible to add files to the listView in ProjectFiles from the main form. I have tried searching the internet for how to do this but everyone has been asking how to do it a different way. I have also tried doing this without help so here is my code but the problem is when I use this code, the software will stop responding.
main form:
public string[] lines { get; set; }
void projectFilesToolStripMenuItem1_Click(object sender, EventArgs e)
{
if (this.parentForm == null)
{
return;
}
if(opfd.ShowDialog()==DialogResult.OK)
{
string[]lines = File.ReadAllLines(opfd.FileName);
}
}
ProjectFiles:
void label1_Click(object sender, EventArgs e)
{
MainForm mf = new MainForm();
{
string[] lines = File.ReadAllLines(mf.lines.ToString());
foreach (string line in lines)
{
listView1.Items.Add(line);
}
}
}
Any help is greatly appreciated. Thanks!
Edit:
I was asked to post exactly what the error is in more detail. Like I said above, the software becomes greyed out, and a message box shows up saying it has stopped responding. If this is not clear enough, please let me know.
Edit: I have tried the below asnwers but the software still continues to do the same. It seems like too much for the software to handle.

First of all, when you call ShowDialog() to display a form, any code after this statement will not execute until that form is closed. See the Remarks section of this
Therefore, it is not possible to add files to the list view in the ProjectFiles from the MainForm in your case (ShowDialog)
But if you need to do that;
Change the access modifier of the listView1 in ProjectFiles to public
Keep the pointer to the ProjectFiles form as a member variable in MainForm
ProjectFiles theProjectFiles = new ProjectFiles();
Display the ProjectFiles form with .Show() instead of .ShowDialog()
theProjectFiles.Show();
Just use the listView1 in ProjectFiles form as usual:
theProjectFiles.listView1.Add(...);

loading a local HTML file into the WebBrowser control keeps causing a loop

I am trying to create my own web browser that opens up a web page I created that is stored locally. I am new to writing in C# and have gotten the browser to work for the most part but I can not get the web page to open. I have tried several different commands and keep getting the same result.This is the command I am using to open the file:
private void webBrowser1_Navigated(object sender, WebBrowserNavigatedEventArgs e)
{
string curDir = Directory.GetCurrentDirectory();
var url = new Uri(String.Format("file:///{0}/{1}", curDir, "START_HERE.html"));
webBrowser1.Navigate(url);
}
The browser opens with no problem but the page keeps loading and doesn't stop. I tried moving the code to the webBrowser1_Navigating instead and it opens the web browser but the page comes up blank. The file is set to copy to Output Directory as Content.
I thought it might be the progress bar and tried several different ways of creating it but keep getting the same results.
This is the code for the Progress Bar:
private void webBrowser1_ProgressChanged(object sender, WebBrowserProgressChangedEventArgs e)
{
try
{
if (e.MaximumProgress != 0)
ProgressBar1.Value = (int)(((double)e.CurrentProgress * 100) / e.MaximumProgress);
if (ProgressBar1.Value < 0)
ProgressBar1.Value = 0;
else if (ProgressBar1.Value > 100)
ProgressBar1.Value = 100;
}
catch (Exception ex)
{
}
}
What can I do to fix the loop? I know I'm missing something but not sure what.

Where your post says
private void webBrowser1_Navigated(...)
do you mean "Navigate" instead of "Navigated"? Because if so, you are causing the loop oby calling Navigate inside of Navigate.

You have to go to the properties for the webBroswer control and remove the event handler that is pointed at webBroswer1.Navigated. You probably don't want to have a navigate command in any event handler associated with navigation as you'll probably have unpredictable looping as you're experiencing.
Put your code in the webBrowser1.ControlAdded. This gets called when the form gets built and the web browser is added to it's parent container. It will only get called once and is independent of the navigation process.

How do I open a window on a new thread?

I have a options window and a window that displays color based on these options and Kinect data. So far everything's on one thread (as far as I know; I haven't done any threading).
Now, I'm adding an option to open a viewer window that will need to be updated with lowest possible latency. All this entails is creating a window and showing it:
viewer = new SkeletalViewer.MainWindow();
viewer.Show();
When this event fires, the color window stops displaying colors (i.e. the event that fires 30 times a second on the main thread stops firing), but the viewer is displayed perfectly. I want the viewer and the color window to both be updated.
From reading other questions, it sounds like the solution is to create the viewer on a new thread. I'm encountering a lot of problems with this, though.
This fires when I click the button to open the viewer:
private void launchViewerThread_Click(object sender, RoutedEventArgs e)
{
Thread viewerThread = new Thread(delegate()
{
viewer = new SkeletalViewer.MainWindow();
viewer.Dispatcher.Invoke(new Action(delegate()
{
viewer.Show();
}));
});
viewerThread.SetApartmentState(ApartmentState.STA); // needs to be STA or throws exception
viewerThread.Start();
}
Regardless of if I just call viewer.Show() or Invoke() it as above, the line throws an exception: Cannot use a DependencyObject that belongs to a different thread than its parent Freezable. Here's how I understand Invoke(): it accesses viewer's dispatcher, which knows what thread the object is running on, and can then call methods from that thread.
Should I be trying to put this viewer on a new thread? Is the problem even a question of threads? The user will not be interacting with the viewer.
Anyone know why this doesn't work? Thanks for the help.

You need to call Show() on the same thread that the window is created on - that's why you are getting the error. Then you also need to start a new Dispatcher instance to get the runtime to manage the window.
private void launchViewerThread_Click(object sender, RoutedEventArgs e)
{
Thread viewerThread = new Thread(delegate()
{
viewer = new SkeletalViewer.MainWindow();
viewer.Show();
System.Windows.Threading.Dispatcher.Run();
});
viewerThread.SetApartmentState(ApartmentState.STA); // needs to be STA or throws exception
viewerThread.Start();
}
See the Multiple Windows/Multiple Threads example at: http://msdn.microsoft.com/en-us/library/ms741870.aspx

So I was running into a similar issue where a new window failed to open on a new thread. The exception was "cannot use a dependencyobject that belongs to a different thread".
The issue ended up being that the window was using a global resource (Background brush). Once I froze the brush resource, the window loaded just fine.

I am not sure if this will solve your problem but can you try creating a thread proc (to open a viewer window) which is executed on a different thread and then have a dispatcher.beginInvoke to update the main window ,
Here is some code-
in the constructor register this
public MainWindow()
{
UpdateColorDelegate += UpdateColorMethod;
}
// delegate and event to update color on mainwindow
public delegate void UpdateColorDelegate(string colorname);
public event UpdateColorDelegate updateMainWindow;
// launches a thread to show viewer
private void launchViewerThread_Click(object sender, RoutedEventArgs e)
{
Thread t = new Thread(this.ThreadProc);
t.Start();
}
// thread proc
public void ThreadProc()
{
// code for viewer window
...
// if you want to access any main window elements then just call DispatchToMainThread method
DispatchToUiThread(color);
}
//
private void DispatchToUiThread(string color)
{
if (updateMainWindow != null)
{
object[] param = new object[1] { color};
Dispatcher.BeginInvoke(updateMainWindow, param);
}
}
// update the mainwindow control's from this method
private void UpdateColorMethod(string colorName)
{
// change control or do whatever with main window controls
}
With this you can update the main window controls without freezing it, Let me know if you have any questions

Removing a Control from a Form

So I've got some serious problems with removing a Control from a Form of my application. It's kinda messed up but I can't change anything. I have a form and I have a separated user Control. The control opens an exe file and shows a progress bar while loading it's bytes. And here comes the problem. I do all of it with a BackgroundWorker and when the worker_DoWorkerCompleted method is called the original form should show a MessageBox and remove the Control.
BackGround_Loader bgLoad = new BackGround_Loader();
bgLoad.Location = new Point(this.Width/2 - bgLoad.Width/2, this.Height/2 - bgLoad.Height/2);
this.Controls.Add(bgLoad);
bgLoad.BringToFront();
bgLoad.AddReferences(this.executableFile, this.SourceReader);
bgLoad.occuredEvent();
At first I set the control's location to be in the middle of the Form itself. Then I add the control to the form, and bring it to the front. After these I send the path of the executable and a RichTextBox's reference to this. With the occuredEvent I start the BackgroundWorker itself. And here comes my problem. I should show a MessageBox in the Form when the in the bgLoad the backgroundworker gets to the DoWorkerCompleted status. Kindly I have no idea how to do it. It works just perfect however the control stays in the middle of the form.

UI actions must be performed on the main UI thread. The events that get raised from the background worker thread are (obviously) in a different thread.
You need something like the following code:
private void backgroundWorker_DoWork(object sender, AlbumInfoEventArgs e)
{
// Check with an element on the form whether this is a cross thread call
if (dataGridView.InvokeRequired)
{
dataGridView.Invoke((MethodInvoker)delegate { AddToGrid(e.AlbumInfo); });
}
else
{
AddToGrid(e.AlbumInfo);
}
}
In this case AddToGrid is my method for adding a row to a DataGridView, but in your case it will be a method that does what you need to do.
Similarly for the backgroundWorker_RunWorkerCompleted method
See this MSDN example

I could find a way to solve the problem but I don't really like it. In the addReferences method I pass the Form itself and an object of the bgLoad class. Then in the RunWorkerCompleted I check if the control is on the form and if it is then I remove it.
bgLoad.AddReferences(this, bgLoad, this.executableFile, this.SourceReader);
...
private void worker_DoWorkerCompleted(object sender, DoWorkerEventArgs e) {
if(this.MainForm.Controls.Contains(this.Control) {
this.MainForm.Controls.Remove(this.Control);
}
}
Like this it works but it's awful for me.