Set the main window’s AllowTransparency to true and set the Background to Transparent.

<Window . . .
    AllowsTransparency="True" Background="Transparent"
    >

Now say you main panel is a grid, put a Border control on it as follows :

<Border Opacity="0.9" . . .>
      <Border.Background>
          . . .
      </Border.Background>
</Border> 

Set the border’s background to what you originally wanted the main window’s background to be. Now you’ll find a transparent window background where your editable controls can still retain 100% opacity.

Warning : Setting AllowTransparency to true on the main window potentially results in some very bad performance issues on both XP and Vista since WPF switches to software rendering (in my experience, even with good video cards). Once that happens, animations and video can get pretty unusably slow.

• C++/CLI HowTo : Deriving from a C# disposable class
• Article mirror on The Code Project

  ref class ManA
  {
  protected:
    NatA* _natA;

    virtual void Init()
    {
      _natA = new NatA();
    }

  public:
    ManA()
    {
      Init();
    }
  };

  ref class ManB : ManA
  {
    NatB* GetNatB()
    {
      return static_cast<NatB*>(_natA);
    }

  protected:
    virtual void Init() override
    {
      _natA = new NatB();
    }

  public:
    ManB()
    {
    }
  };
}

Now, if you do a gcnew ManB() you’ll see that ManB::Init is called first (this is done during the base class ctor) and then ManB’s constructor is called. Of course this means that you should not access any member in ManB that needs to be created or initialized in the constructor. In fact this is probably not a good practice at all - but the poster asking this question had a special requirement and this was one straightforward way to address his problem. Note that C# users won’t find this particularly odd because this is just the way C# behaves too. This behavior is dictated by the fact that the CLR works with vtables directly, and both C# and C++/CLI just followed the curriculum.

• Using a TypeDescriptionProvider to support dynamic run-time properties

private int _age;

void Foo()
{
    int age;
    //...
    if(age > _age) // <-- My way
    {
        //...
    }
}

private int age;

void Foo()
{
    int age;
    //...
    if(age > this.age) // <-- Joe's recommendation
    {
        //...
    }
}

While I did think that was a fair approach, I am still not convinced it’s fully alright since the onus is on the coder to remember to do this - there’s nothing stopping him from forgetting to prefix this for member fields. So for the time being I am going to continue using underscore for private members.

private void MainForm_Load(object sender, EventArgs e)
{
    TextBox textBox = new TextBox() { Multiline = true, Dock = DockStyle.Fill };
    this.Controls.Add(textBox);
    this.Controls.SetChildIndex(textBox, 0); // move it to the 0th position
}

• A look at STL/CLR performance for linear containers

The next few minutes he proceeded to converse with me about how lots of Indians were in the US these days on H1 Visas, how a lot of them went on to get Green Cards, how he recently moved to Atlanta from Arkansas, how he’d be delighted to introduce his wife to me (apparently she was elsewhere in the store at that time) and a few other topics that I don’t remember right now. All I remember thinking was how to get out of this conversation, especially since I had a sneaking suspicion that this guy was trying to sell some Amway like pyramid scheme on me. Fortunately Smitha called for me at that moment and I used this opportunity to say goodbye to him, but before I could do so he handed me his business card and asked me for mine. I did not have one with me and when I said that to him, he quickly produced a piece of paper and a pen out of nowhere - honestly, I didn’t see where he took it out from, he was like a conjurer - conjuring pen and paper out of thin air. With heavy misgivings I wrote my first name and phone number on his magically produced piece of paper and gave it to him and we parted.

Needless to say, Smitha gave me a quick firing-down for giving my number to a stranger, but fortunately enough she was soon distracted by a shelf containing the oddest looking ladies’ purses I have seen in a while. Normally this would have worried me since I definitely didn’t want her carrying around one of those revoltingly unattractive purses, but at that point I was just relieved to get out of her firing line. Just then I noticed a middle aged Indian woman conversing with a young, pretty and trendily dressed Indian girl (looked like she was in her early 20s). Now I don’t want to come across as someone who eavesdrops when 2 strange women are conversing in front of me, but I couldn’t help catch a few odd words here and there. It didn’t take me too long to realize that this woman was basically dishing out the same stuff to this girl that the strange guy had earlier dished out to me, and in a minute or so I saw the hapless girl hand over her phone numbers to this lady (I distinctly remember her explicitly specifying her land, work and cell numbers). I was certain that this middle aged lady was the earlier gentleman’s spouse and at that point it became increasingly evident that they were soliciting phone numbers from Indian looking folks.

My suspicions were confirmed a little later when we left Target with Smitha’s shopping picks for the day. The middle aged couple were walking together towards the parking lot, and most markedly they did not have a single item with them (forget a bag). They had basically spent close to an hour inside Target seeking out potential Indian victims (who they hoped would be new enough to the country) and collecting their information. I fully expect to receive a phone call this week inviting me to a gathering of some sort where this gathering would most definitely be a sales talk for some crappy pyramid scheme. Obviously I would get out of it with a clever excuse but I really do feel sorry for the pretty young girl who did seem naïve enough to fall into this trap. Oh well, I suppose she will eventually learn that strange Indian looking people approaching you in the middle of a store and asking you if you are from India are to be treated with the deepest mistrust and skepticism possible. Oh, and we are going to Target this evening - Smitha wants to return a hand bag that she took half an hour to select, apparently she did not like it when she looked at it this morning and so wants a new one. Sigh!

• Deploying MFC applications via ClickOnce

Anyway I have re-read the book a few times now, some parts of it several times, some parts of it maybe a couple of times, and with each iteration I ended up with a “hey that makes sense now” feeling. I spent the last few days of this Christmas/New Year holiday re-reading the entire book and this was probably my best experience so far. I instinctively recognized familiar patterns that I had seen in use in MFC and the .NET class library, and I also began to understand certain patterns better (even those that I was previously sure I understood). I don’t think I’ve fully got it even now, but I have concluded that the key to getting design patterns is probably to apply them in many different scenarios and perhaps occasionally coming back to the book and giving it a quick read (1-2 hours should be good enough to scan the entire book and refresh your memory). And though design patterns is a subject that has been covered once too often in various blogs and articles I may occasionally blog about my attempts at applying known patterns to specific problems. That I guess would be my new year resolution (or at least one of a dozen others).

• Download the compiled application
• Download the application source code
• See the application related article on my website

• Using data selectors to create a listbox with expand/collapse support

<Window x:Class="..."
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    ...
    MinWidth="700" WindowStyle="None" Icon="...">

I then define a user control that will act as the title bar and place it on top of the window. Adding maximize/restore, minimize, and close buttons is not a biggie. You just need to remember to toggle the maximize button with restore (to match normal windows behavior). All you need to do is to set WindowState to WindowState.Minimized, WindowState.Normal, or WindowState.Maximized as required. You might also want to handle double-click and route it to the maximize/restore handler (again to match windows behavior). The one final step would be to handle title bar based drag. To do that, handle the MouseDown event and do this :-

void TitleBar_MouseDown(object sender, MouseButtonEventArgs e)
{
    if(e.ChangedButton == MouseButton.Left)
        Application.Current.MainWindow.DragMove();
}

CMenu* pSysMenu = GetSystemMenu(FALSE);
if (pSysMenu != NULL)
{
    pSysMenu->RemoveMenu(SC_MOVE, MF_BYCOMMAND);
}

Obviously, you need to think of why you’d want to do soemthing like this. I personally would find it very annoying if some app I installed prevented me from moving its main dialog. Though perhaps it would be okay if there was a way to minimize the app. An alternate way would be to prevent the dialog from moving via the mouse, but to still enable keyboard-based moving. To do that, we handle WM_NCHITTEST and do something like this :-

LRESULT CUnmovableDlg::OnNcHitTest(CPoint point)
{
    LRESULT result = CDialog::OnNcHitTest(point);
    return result == HTCAPTION ? HTCLIENT : result;
}

We treat HTCAPTION like HTCLIENT, so now the user cannot drag/move using the title bar. He can still move it via the keyboard (assuming you have not removed SC_MOVE). Once again, unless you have a very good reason, this is not something I would recommend at all.

ScrollViewer scrollViewer = FindChildControl<ScrollViewer>(searchResultsListbox);

And here’s the function listing :-

private T FindChildControl<T>(DependencyObject outerDepObj) where T:DependencyObject
{
    T child = null;

    for (int index = 0; index < VisualTreeHelper.GetChildrenCount(outerDepObj); index++)
    {
        DependencyObject depObj = VisualTreeHelper.GetChild(outerDepObj, index);

        if (depObj is T)
        {
            child = depObj as T;
        }
        else if (VisualTreeHelper.GetChildrenCount(depObj) > 0)
        {
            child = FindChildControl<T>(depObj);
        }

        if (child != null)
        {
            break;
        }
    }

    return child;
}

double pointSize = (double)new FontSizeConverter().ConvertFrom("8pt");

• A data-bound multi-column combobox

It’s fairly easy to use and all you need to do is to set the DataSource property. The control will auto-populate the columns from the columns (if any) in the DataSource.