Re: property exists (OnPaint followup)

I'm annoyed (in many ways) that the Infragistics controls aren't more
clearly thought out on things like this.  I mean, almost all of their
controls have an 'Appearance' object that is useful (it groups many
'neat' look features together for the control).  However, the properties
that the Appearance object holds that are essentially 'pass-throughs'
for the underlying control properties (like BackColor, ForeColor, font,
etc.) should still exist.

I understand the thought behind what you are suggesting - however, a
slight twist.  As I mentioned, there are plenty of Infragistics controls
that could be used as a canvas for what I'm doing (just as there are
several VS controls).  Every Infragistics control that could be used as
a canvas will have an Appearance property.  It would be much cleaner to
try to discover not whether the canvas control can be cast to the many
Infragistics controls but instead to discover whether the canvas control
had an 'Appearance' property.

Any good way to do this?

Peter

-----Original Message-----
From: Discussion forum for developers using Windows Forms to build apps
and controls [mailto:[email protected]] On Behalf Of
Fabian Schmied
Sent: Wednesday, May 23, 2007 10:46 AM
To: [email protected]
Subject: Re: [DOTNET-WINFORMS] property exists (OnPaint followup)

> As a follow on to my painting question, I need to obtain the
'BackColor'
> of the hosting 'canvas' control.  For the VS controls, this is simple
> since there is a BackColor property.  For other controls that changed
> the name of the 'BackColor' property or that have the BackColor
property
> another level deep in their object model, it isn't quite as simple.
>
> For example, the infragistics control I want to use as the canvas
> exposes the BackColor property inside an 'Appearance' property.
>
> So for the System.Windows.Forms.Panel object, I get the BackColor from
>
> Color myColor = _canvas.BackColor;
>
> For the Infragistics.WinGroupBox object, I get the BackColor from...
>
> Color myColor = _canvas.Appearance.BackColor;
>
> If the 'Appearance' property exists for the object assigned to
_canvas,
> then I will use it.  So what I am asking is, how do I check to see if
> the object '_canvas' has a property called 'Appearance'?

You'll notice when the C# compiler gives an error.

In a programming language like C#, if you have a canvas variable of
type "Control", you can only invoke methods directly supported by the
Control class.

I.e.:
Control _canvas = ...;
Color myColor1 = _canvas.BackColor; // compiles
Color myColor2 = _canvas.Appearance.BackColor; // gives a compilation
error

In order to access the Appearance property, the "_canvas" variable
must be of a type which supports that property. In C#, you need to
cast the object to such a type. If you are not sure the cast will
succeed, you can use the "is" or "as" operators to test it:

Control _canvas = ...;
...
Color myColor;
// test whether _canvas implements the InfragisticsControl type
InfragisticsControl _infragisticsControl = _canvas as
InfragisticsControl;
if (_infragisticsControl != null)
{
  // yes, so use Appearance
  myColor = _infragisticsControl.Appearance.BackColor;
}
else
{
  // no, use Color
  myColor = _canvas.BackColor;
}

(Note that I don't know Infragistics' controls, so the solution I'm
proposing might not work exactly that way.)

Regards,
Fabian