Hi, I browsed for a related question/answer without luck, so here it goes:
Is there a known pattern that would allow me to promote an object of class A
to subclass B which inherits from A?
In other words, how can I turn a point into a circle or a dog into a

This is for a Win form.
How do I check if the date variable is null?
                       DateTime dtDOB = (DateTime) dgSportsman[rowNum, 8];

I defined:
Hashtable chan1 = new Hashtable(new  
CaseInsensitiveHashCodeProvider(CultureInfo.InvariantCulture), new  
InvariantComparer());

I'm consuming webservice which returns a large dataset.
- 1st step was a synchronous call.
- 2nd step was making it asynchronous with this method
 (http://www.xamlon.com/kb/Article.aspx?id=10157)

I have to convert an ASP web app to a asp.net web app using C#, are there
any tools out there to do this or is this a full re-write?

I have a panel with a auto scroll bar, inside the panel I have multiple
labels anda a small datagrid, and I can't scroll the panel up or down using
the middle mouse button, can someone tell me how to do it?
Or at leasat give me a hint?

i have a jpeg image that i want to resize, but not lose any quality (or
as little as possible).  i found a lot of samples out there that resize
an image, but most of them basically kill the quality.  my application
will be for photographs; i want to scale an image from, for example,

Hi again,
I've asked this question before, but I think I'd better rephrase.  I've just
clicked a column header in my DataTable/DataGrid and the column is sorted.  
Pre-sort, I got the file number from the File column (xFile - which doesn't

When you click on a column header to sort in ascending or descending order,
numbers (and dates) aren't sorted correctly.  It turns up like this:
1
10

Are there any built in time and/or date validation methods that one can make
use of in .NET?
thanks folks
LDD

The user to only select items in collection of a combo box.
My combo box was "AM" and "PM" in the Items property. I want the user only
to be able to type in "AM" or "PM".  Right now I can type anything in the
combo box, like "QQ".  How do I force the combo box to only allow items ...

I build a web form with a 4-cell table on the top (flawlayout), followed by
some labels and textboxes (gridlayout). The web form is displayed well in
dell m60 laptop with all resolution options and DPI options. However when I
tried to run it in a dell P3 desktop, labels and ...

Is it possible to create a public Hash Table in Windows Forms?
I.e., I place the Hash Table construction in the constructor of the
form.  But I would like to be able to reference it later in another
class (i.e., not reconstruct it everytime).

I'm new to C# and this question is very elementary.  In the code below,
CreateGraph is a button click event handler and Form1_Paint creates a
graphics object and draws a few lines.  When the user clicks the button
(handled by CreateGraph), the graph is to be drawn on the form.  ...

In this code:
XmlTextWriter myWriter = new XmlTextWriter(@"C:\Xmldata\myWriter.xml",
null);
Why do they have the @ at symbol?  Why not just the string?