Code Question 70-316 Amit Kalani Book

hey all,

have a code "convention" question, and was wondering if
it's done this way as a "Best Practices Approach", and/or
what the advantage is for doing it this way.

Here's the example code from Amit's 70-315 book:

private void dudColor_SelectedItemChanged(object sender,
System.EventArgs e)
{
//Typecast the object to DomainUpDown
DomainUpDown dudColor = (DomainUpDown) sender;
//Change color of lblsampleText to selected color
lblSampleText.ForeColor = Color.FromName
(dudColor.Text);
}

private void nudSize_ValueChanged(object sender,
System.EventArgs e)
{
//Typecast the object to NumericUpDown
NumericUpDown nudSize = (NumericUpDown) sender;
//Change the font of lblSampleText to selected
font
lblSampleText.Font = new Font
(lblSampleText.Font.FontFamily, (float) nudSize.Value);
}

OK, I understand the code completely, but why is the
sender cast to a new instance of the same object, when
you can just directly access the 'sender' like this:

private void dudColor_SelectedItemChanged(object sender,
System.EventArgs e)
{
lblSampleText.ForeColor = Color.FromName
(dudColor.Text);
}

private void nudSize_ValueChanged(object sender,
System.EventArgs e)
{
lblSampleText.Font = new Font
(lblSampleText.Font.FontFamily, (float) nudSize.Value);
}

The only advantage I can see to using the first approach,
casting the sender is if you are attaching this event to
multiple objects ... then you would be able to use this
same set of code to make programmatic changes
polymorphically (for any sender sent in).

Thanks,
Pete

PS-sorry if formatting is off!

 

Pete,
did you actually try your code and compiled it? dudColor
and nudSize are both locally declared inside their
respective events, in your code sample.

I guess you just can't use sender.Text or sender.Value
(inside the events) directly. You must have to declare a
local DomainUpDown and NumericUpDown (or other object) and
casting sender to the appropriate object. If you use the
class declares dudColor and nudSize then you won't have
the current Text or Value (that are stored in sender),
coming from the event.

Make sense?
Jackie