Develop Reference

How can I control or stop the paint event of the dynamic user control from the main form?

I have a big problem with a small matter. I'm coding a messaging app.
This is the layout I use:
Main Form --> container (UserControl) --> bubble(UserControl)
I am sending these parameters to the container
this.container1.addOutMessage(message, get_min_sec(time), tickStatus);
and container creates bubbles dynamically in itself.
public void addOutMessage(string message, string time, int tick_status) {...}
According to the suggestion I got in this forum, I draw the contents of the message bubbles in the Paint event. Since the width and height information was not yet clear when creating, I could not create the vertical distance between the messages correctly.
That's why I created this function.
public void ContaninerConfigure()
{
int counter = 0;
int keepBottom = 0;
foreach (var item in container1.panel.Controls.OfType<Control>().OrderBy(ee => ee.TabIndex))
{
//SuspendDrawing(item);
if (item != null)
{
if (counter != 0)
{
item.Top = keepBottom + 10;
keepBottom = item.Bottom;
}
else keepBottom = item.Top + item.Height;
}
counter++;
}
counter = 0;
}
then
My problem starts here. When I add it to the container's resize event it works fine but when I call it in the main form after my messages are loaded it doesn't work at all. Paint event continues to run on every scroll movement. In the container's resize event, only the message bubbles that appear on the screen are aligned. It can crashes again when I scroll up. Then it is necessary to call the previous function again to align it.
I did not access Paint event in Bubble(UC) which is dynamically created in Container(UC).That's why I couldn't control with the paint event, its run or stop.
After some research I found the SuspendDrawing method. I implemented it this way but I don't want to use it. It takes 3 seconds for 25 bubbles to line up on the panel and main form stays "up to date" during compile.
There has to be a more practical way of doing this. For example, I don't know how to check the bool in the bubble(UC) from the main form.
If you have any idea about this issue, please help.

Recreate a group of Controls

Let's say that I have a panel with like... 3 controls in it. I may end up adding more controls to it or changing the positioning within that panel. When the program starts, I will programmatically HIDE the control. Eventually, the user can click a button that will create a duplicate of the original panel to populate an area on the form. The button should have the option for another click eventually, meaning that multiple instances of these can come about to populate this area. Remember that these controls may have text labels within them that can be individually set or altered later on, programmatically. I am assuming that to do this program, I need to make a List of controls, maybe a List of panels? I'm not exactly sure how to do this considering the fact that I need multiple controls duplicated multiple times.
Is there a nice, simple way to do this? I really don't want to do the duplication with any kind of 3rd-party package.

You will have to do it in code and therefore it'll be as nice as you can code ;-)
Seriously the course most often taken is to
create a UserControl which is a class related to a form, with the layout you want..
..and add more and more instances of it..
..often to a FlowLayoutPanel, often with AutoScroll
This is pretty nice and simple imo.
Here is a short walk-though..:
first we start, as usual, by picking a nice name for the UserObject class, maybe 'DataPanel' or 'BookItem'..
Next we create it: Go to the project explorer and right-click, choosing Add-New UserControl and give it the class name you chose. I'll use 'BookItem'.
Now you can see the Designer showing you a small empty control.
Look closer: You can also see that in the project explorer ther is now not only the new 'BookItem.cs' file but also the complementary 'BookItem.Designer.cs' and even a 'BookItem.resx' file; so this works very much like creating a new Form..
Let's add a few controls from the toolbox, I chose to add a PictureBox, four Labels and a NumericUpDown.
Have a look at the BookItem.Designer.cs file: Here you can see the very things you see in a Form.Desginer.cs file: All settings and all declarations for all controls you add to the layout. Note especially the declarations (at the bottom of the file): Just like for a Form, all controls by default are declared as private!
We can now work on the layout and script the controls. We also can add functions and properties to the UC, just like a Form.
Please note: Anything you need to access from outside, read from your form or its methods must be public! So if you want to access the NUpDown, let call it 'nud_quantity' you have a choice
You can change its declaration in the BookItem.Designer.cs from private to public or in the Designer by changing the Modifiers property
Or you can write a public function in the UC to get/set its value
Chosing between those two ways is a matter of taste; if other developers will work with the UC class, it will probably be better to put close control over what you expose by writing access methods.
After you have compiled the project you can see the new UC in the Toolbox.
You can now either add it from the Toolbox or
you can add it in code like any control you create dynamically.
Let's look at an example:
Imagine a simple order system in a bookstore: The customer has done a search on the books in our store and is presented with a list of books in a DataGridView 'dgv_bookList', readonly, multiselect. To the right there is a FlowLayoutPanel 'flp_cart' represeting a shopping cart. And we have a command button 'cb_addItems' to add selected books to the cart.
The Button might be scripted like this:
private void cb_addItems_Click(object sender, EventArgs e)
{
if (dgv_bookList.SelectedRows.Count <= 0) return;
foreach (DataGridViewRow row in dgv_bookList.SelectedRows)
{
BookItem book = new BookItem (row);
book.label1.Text = "#00" + book.label1.Text;
book.Name = book.label1.Text;
flp_cart.Controls.Add(book);
}
}
This will add one BookItem for each selected row in the DGV.
A few things to note on the above code:
I pass a DataGridViewRow into the constructor of the UC so it can directly set its labels! This means that, in addition to the parameterless contructor the desginer has built for us, we need to write a second contructor, maybe like this:
public bookItem()
{
InitializeComponent();
}
public bookItem(DataGridViewRow bookData)
{
InitializeComponent();
label1.Text = bookData.Cells[0].FormattedValue.ToString();
label2.Text = bookData.Cells[1].FormattedValue.ToString();
label3.Text = bookData.Cells[2].FormattedValue.ToString();
label4.Text = bookData.Cells[3].FormattedValue.ToString();
}
Instead you could write a public setData(DataGridViewRow bookData) function.
Also note how stupid my labels are named! You can do better than that, I hope!
Also note how I access 'label1' and modify its Text from a Button in the Form; to do that I had to change its declaration in the Desginer.cs file:
private System.Windows.Forms.PictureBox pb_cover;
public System.Windows.Forms.Label label1; // <<----expose this label !
private System.Windows.Forms.Label label2;
private System.Windows.Forms.Label label3;
private System.Windows.Forms.Label label4;
private System.Windows.Forms.NumericUpDown numericUpDown1;
Often preferrable: An access function, maybe like this:
public int quantity() { return (int) numericUpDown1.Value; }
Or, of course a Property:
public int quantity { get { return (int)numericUpDown1.Value; } }
Also note, that I set the Name of the BookData item to some variant of the 1st data item, my book id. This might as well, or better, happen in the constructor; and there should be a check to prevent adding the same item twice..
All in all one can say, that using UserControls is very much like working with Forms, including all the usual ways or tricks for inter-form communication: keep references, expose members, create properties and functions..
One final Note: Like with forms or subclassed controls there is one catch: By placing them in the designer, you assign the designer the responsiblity to display your UC during design time.
This is normally just fine; however it is also possible to introduce subtle mistakes which make it impossible for the designer to display the control. You need to correct these problems before the designer will be able to show a control or any form that contains it. Let have a look at a simple example of such a problem:
Let's script the Paint event of the PictureBox 'pb_cover' in the UC:
public Brush myBrush = null;
private void pb_cover_Paint(object sender, PaintEventArgs e)
{
if (pb_cover.Image == null)
{
Size s = pb_cover.ClientSize;
e.Graphics.FillRectangle(myBrush, 0, 0, s.Width, s.Height);
e.Graphics.DrawLine(Pens.Red, 0, 0, s.Width, s.Height);
e.Graphics.DrawLine(Pens.Red, s.Height, 0, 0, s.Width);
}
}
And let's modify the code in the Add button:
BookItem book = new BookItem (row);
book.label1.Text = "#00" + book.label1.Text;
book.myBrush = Brushes.OliveDrab;
flp_cart.Controls.Add(book);
Now, if you run the program all will be fine. Even if you try to look at the UC in the designer there may or may not be problems. But once you try to open a Form on which the UC was placed, the Desginer will crash and tell you that it can't work, since the Brush is null. Here the remedy is simple: add a default value to the Brush declaration and all is well. Other situations may need a little more thinking..
I don't even run into the problem btw, since I have not placed an instance of BookItem on the Form; they are only created in the Add Button..
I hope that gets you started!

C# WPF Frame->UserControl->Usercontrol Loaded event doesn't fire

I'm new into WPF and have a problem I can't seem to find a solution for.
I'm writing a G19 (Keyboard) applet. This Keyboard has a 320x240 display attached, which you can access with C#.
I'm using WPF for this, because I don't need to do any GDI drawing anymore and use the normal controls instead.
So. It works as I wish. Everything draws properly except one UserControl. I have downloaded this control -> http://marqueedriproll.codeplex.com/
In the designer, the control works, the Loaded event get's fired and the animation is good.
When I run my application, I just see the label and the text. The animation does not work, and the Loaded event does not fire anymore.
Any help is appreciated.
The main function is my wrapper. The wrapper is already a Usercontrol and displays plugins which are switchable. This wrapper has the Frame Control(Wrapper1). I replace the content of this frame every time I switch the plugin.
public void SetPlugin(IPlugin plugin)
{
if (this.MainPlugin != null)
{
this.MainPlugin.OnHide();
((UserControl)this.MainPlugin).Visibility = System.Windows.Visibility.Hidden;
}
this.MainPlugin = plugin;
((UserControl)this.MainPlugin).Visibility = System.Windows.Visibility.Visible;
this.MainPlugin.OnShow();
this.Wrapper1.Content = this.MainPlugin;
}
I think it's the right approach to handle a plugin system that way. The plugin get's drawed on my keyboard.
What I don't understand is why the usercontrol only works in the designer view and not in the running application.
The basic code of the scrolling label is so:
public MarqueeText()
{
this.Loaded += new RoutedEventHandler(MarqueeText_Loaded);
InitializeComponent();
canMain.Height = this.Height;
canMain.Width = this.Width;
}
void MarqueeText_Loaded(object sender, RoutedEventArgs e)
{
StartMarqueeing(_marqueeType);
}
I don't see a reason why it doesn't work. Actually Ive always found a way to fix a problem but this time I see nothing.
Thanks in advance. Your help is really required today.
Have a great saturday! :)

I am guessing you are rendering to a bitmap target, rather than onscreen. If you are using RenderTargetBitmap, you have a couple of responsibilities. You need to set both a presentation source, and make sure you run events on the dispatcher.
Normally, App.xaml or Application.Run does this for you, but if you are not using a Window, you are on your own.
See this related question for details.

When Control.ParentChanged Event occurs?

I read about Control.ParentChanged Event on MSDN
http://msdn.microsoft.com/en-us/library/system.windows.forms.control.parentchanged(VS.71).aspx
But I don't understand the sample code: there's no ParentChanged at all appearing in source code ?
private void currencyTextBox_TextChanged(object sender, EventArgs e)
{
try
{
// Convert the text to a Double and determine if it is a negative number.
if(double.Parse(currencyTextBox.Text) < 0)
{
// If the number is negative, display it in Red.
currencyTextBox.ForeColor = Color.Red;
}
else
{
// If the number is not negative, display it in Black.
currencyTextBox.ForeColor = Color.Black;
}
}
catch
{
// If there is an error, display the text using the system colors.
currencyTextBox.ForeColor = SystemColors.ControlText;
}
}
So I don't understand what Control.ParentChanged Event is or does.

Hehe, they just couldn't come up with a good example. And punted by showing a generic FooChanged event handler instead. Yeah, useless.
It is quite unusual to implement a ParentChanged event handler yourself. It's a big deal in the Winforms internals, properties like BackColor, ForeColor, Font are 'ambient' properties. If they are not overridden from the default then they'll get the value of the Parent. Which of course means that it is really important to notice that the parent changed. The winforms code already takes care of it, you very rarely have to worry about it. Unless you create your own ambient property of course.

There would be another piece of code elsewhere that registers this as an event handler:
currencyTextBox.ParentChanged += new EventHandler(currencyTextBox_TextChanged);
However, I agree - the method name is misleading.
This event handler will fire when you change the parent control of this control to a different parent control.
You may want to read up on raising and consuming events.

What is the last event to fire when loading a new WPF/C# window?

I am trying to load a preferences window for my application and I would like the apply button to initially be disabled, then when a preference is updated, the apply button gets enabled again. I have some controls data bound to a preferences object and what happens is that after the window loads, the combobox events get triggered. Is there any event that is guaranteed to happen dead last after everything is stable?
Here is what my code looks like (the apply button is always enabled after the window loads):
private void Window_Loaded(object sender, RoutedEventArgs e)
{
_preferencesData = new PreferencesDataContext();
LayoutRoot.DataContext = _preferencesData;
ButtonApply.IsEnabled = false;
}
private void ComboBox_SelectionChanged(object sender, System.Windows.Controls.SelectionChangedEventArgs e)
{
ButtonApply.IsEnabled = true;
}
Is it also interesting to note that this only happens with textboxes and comboboxes, not checkboxes or radiobuttons.

Best solution for simple need
Joseph's answer is the best solution by far for your simple need: Just use data binding and let the data model handle it.
Answer to question as posed
There are more complex scenarios when you really do need control after absolutely everything has finished loading and all events have fired. There is no single event that occurs "dead last", but it is easy to effectively roll your own using the Dispatcher queue.
This is how to do it:
Dispatcher.BeginInvoke(DispatcherPriority.ContextIdle, new Action(() =>
{
var x = ComputeSomething(1, 2, 3);
DoSomething(x, "Test");
}));
Everything inside the { } will be executed when WPF finishes everything at a higher priority than ContextIdle, which includes all event handlers, loaded events, input events, rendering, etc.
Sequence of events when a Window is created and shown
As requested, here is the sequence of major events in WPF when a window is created and shown:
Constructors and getters/setters are called as objects are created, including PropertyChangedCallback, ValidationCallback, etc on the objects being updated and any objects that inherit from them
As each element gets added to a visual or logical tree its Intialized event is fired, which causes Styles and Triggers to be found applied in addition to any element-specific initialization you may define [note: Initialized event not fired for leaves in a logical tree if there is no PresentationSource (eg Window) at its root]
The window and all non-collapsed Visuals on it are Measured, which causes an ApplyTemplate at each Control, which causes additional object tree construction including more constructors and getters/setters
The window and all non-collapsed Visuals on it are Arranged
The window and its descendants (both logical and visual) receive a Loaded event
Any data bindings that failed when they were first set are retried
The window and its descendants are given an opportunity to render their content visually
Steps 1-2 are done when the Window is created, whether or not it is shown. The other steps generally don't happen until a Window is shown, but they can happen earlier if triggered manually.

The Window.ContentRendered event fulfilled my requirements.

I just did kind of the same thing behaviorly in a systray WPF app.
However, I didn't do it using event handling. I simply bound the Enabled property of my button to a property in my ViewModel, and had the property updated whenever I needed the behavior.

You can use ManagedSpy to figure this out on your own.
http://msdn.microsoft.com/en-us/magazine/cc163617.aspx

Setting the DataContext will likely fire the SelectionChanged event, and you can't rely on when exactly it's fired. Some logic checking on what exactly is selected would be more reliable:
private void ComboBox_SelectionChanged(object sender, System.Windows.Controls.SelectionChangedEventArgs e)
{
if (myComboBox.SelectedItem == null)
{
buttonApply.IsEnabled = false;
}
else
{
buttonApply.IsEnabled = true;
}
}
The reason it's happening afterwards with your code as-is is because the event gets queued on the thread for the UI, so it's up to Windows if it will execute the next line of code in Load, or to handle the other events on the queue.

Not to throw a whole lot of stuff at you that you may or may not be familiar with, but if this is a relatively new codebase, you may want to consider using the MVVM pattern and use Commands instead of the archaic (emphasis mine) eventing model.

Order of Events in Windows Forms
Control.HandleCreated
Control.BindingContextChanged
Form.Load
Control.VisibleChanged
Form.Activated
Form.Shown