Connecting a C# code behind file to the declarations of controlsin XAML.

Hi all,

I'm trying to develop a TicTacToe example as show in the Sells O'Reilly
book, Chapter 5. He's just updated his sample code from his book to
make the examples compatible with the November CTP. I've just tried
typing out one of his simple examples and it keeps crashing for me,
however downloading his example code and running it works fine.

I've traced the difference to the following method:

void System.Windows.Serialization.IComponentConnector.Connect(int
connectionId, object target)

which is found in the generated .g.cs file for my Window. When I create
a new project in VS 2005, it gives me an Application (MyApp) and a
window (Window1), each with a .xaml file and a .xaml.cs code behind
file. Let's say I add a few buttons to the window using XAML:

<Button Grid.Row="0" Grid.Column="0" x:Name="cell00" />
<Button Grid.Row="0" Grid.Column="1" x:Name="cell01" />
<Button Grid.Row="0" Grid.Column="2" x:Name="cell02" />

I also have some code in the constructor of the Window1.xaml.cs file
that attempts to access those buttons in C# code:

public Window1()
{
InitializeComponent();

this.cells = new Button[] { this.cell00, this.cell01,
this.cell02 };

foreach (Button cell in cells)
{
// do something with the button
}
}


When the application runs, a method is created in the Window1.g.cs file:

void System.Windows.Serialization.IComponentConnector.Connect(int
connectionId, object target) {
switch (connectionId)
{
case 1:
this.cell00 = ((System.Windows.Controls.Button)(target));
return;
case 2:
this.cell01 = ((System.Windows.Controls.Button)(target));
return;
case 3:
this.cell02 = ((System.Windows.Controls.Button)(target));
return;
}
this._contentLoaded = true;
}

The purpose of this method seems to be to "wire" the buttons
instantiated in XAML to references in .g.cs so that you can use those
references in your C# code behind.

All good, right? So here's the problem. In the example from the
Sell's book, the Connect() gets invoked when InitializeComponent() is
called. I can't find the actual method call, I guess it's buried deep
the WPF framework somewhere. However, in my own example, Connect()
doesn't seem to be invoked until after the constructor of my class
returns. What this means is that I am unable to reference any of the
controls declared in XAML from the constructor of the C# code behind file.

Can anyone think of what would account for the difference? I've
scrutinized the Window1.xaml.cs and Window1.g.cs files and can't find
any differences. There must be some parameter somewhere that Sells set,
but I don't know about...

Regards,
Jason

Jason Dolinger wrote:

> I also have some code in the constructor of the Window1.xaml.cs file
> that attempts to access those buttons in C# code:

That is your problem right there. You cannot touch the buttons until the
Window's Loaded event fires (usually you hook up in that event). It's fired
after the control tree is deserialized, anytime before that is too soon.

HTH,
Drew

Drew Marsh wrote:
> Jason Dolinger wrote:
>
>> I also have some code in the constructor of the Window1.xaml.cs file
>> that attempts to access those buttons in C# code:
>
>
> That is your problem right there. You cannot touch the buttons until the
> Window's Loaded event fires (usually you hook up in that event). It's
> fired after the control tree is deserialized, anytime before that is too
> soon.
>
> HTH,
> Drew
>
>

Thanks Drew, that was what I had thought the case was (you'd actually
answered that one for me in a previous post). But I clearly have this
code example that I downloaded from
http://www.sellsbrothers.com/writing/avbook/ where that doesn't seem to
be the case.

In the window's constructor there is a call to InitializeComponent()
(defined in the Window.g.cs file). Somehow that call also calls the
Connect() method. If you put a breakpoint in Connect(), it stops there
as I try to step over the InitializeComponent() call.)

When I code this from scratch, that does not happen and the behavior is
as you describe it should be. I'm just trying to understand what could
be the possible differences here.

Thanks!
Jason