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.NET windows forms interview questions
1) I am
constantly writing the drawing procedures with
System.Drawing.Graphics, but having to use the try and
dispose blocks is too time-consuming with Graphics objects.
Can I automate this? Yes, the code
System.Drawing.Graphics canvas = new System.Drawing.Graphics();
try
{
//some code
}
finally
canvas.Dispose();
is functionally equivalent to
using (System.Drawing.Graphics canvas = new
System.Drawing.Graphics())
{
//some code
} //canvas.Dispose() gets called automatically
How do you trigger the Paint event in
System.Drawing?Invalidate the current form, the OS will take
care of repainting. The Update method forces the repaint.
With these events, why wouldn’t Microsoft combine Invalidate
and Paint, so that you wouldn’t have to tell it to repaint,
and then to force it to repaint? Painting is the slowest
thing the OS does, so usually telling it to repaint, but not
forcing it allows for the process to take place in the
background.
How can you assign an RGB color to a System.Drawing.Color
object? Call the static method FromArgb of this class and
pass it the RGB values.
What class does Icon derive from? Isn’t it just a Bitmap
with a wrapper name around it? No, Icon lives in
System.Drawing namespace. It’s not a Bitmap by default, and
is treated separately by .NET. However, you can use ToBitmap
method to get a valid Bitmap object from a valid Icon
object.
Before in my VB app I would just load the icons from DLL.
How can I load the icons provided by .NET dynamically? By
using System.Drawing.SystemIcons class, for example
System.Drawing.SystemIcons.Warning produces an Icon with a
warning sign in it.
When displaying fonts, what’s the difference between pixels,
points and ems? A pixel is the lowest-resolution dot the
computer monitor supports. Its size depends on user’s
settings and monitor size. A point is always 1/72 of an
inch. An em is the number of pixels that it takes to display
the letter M. |
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