Anybody know of a good 3rd Party grid control that supports AutoFill (like Excel does). Also a good export to Excel and import (paste) from Excel would be handy also. I'm mainly interested in a WinForms grid that can do this, but would also be curious if there is a Silverlight grid or ActiveX grid with AutoFill capabilities.
If you are going to be providing 'export to Excel and import (paste) from Excel ' then does that mean that you're delivering to an environment where your users have a guaranteed installation of Excel on their machines? If so, you could look at using Excel itself as the grid you want, either via a VSTO project or by perhaps embedding an Excel sheet as a control a WinForm? The latter might require jumping through a few interop hoops but I think it's still possible.
Obviously, if it's not guaranteed that all your users will have Excel on their machines then you can disregard my answer ;-)
SpreadsheetGear for .NET is an Excel compatible spreadsheet control for WinForms which can also be used in ASP.NET applications. It supports autofill (drag fill with mouse as well as API) which is compatible with Excel as well as a Data Series command / UI / API which handles more complex cases including linear and growth trends, dates / times, etc...
SpreadsheetGear also supports reading from, writing to xls and xlsx as well as clipboard support (Cut, Copy & Paste) which can handle Excel content on the Windows clipboard.
We do not have a SpreadsheetGear for Silverlight control yet - but that is a high priority for the future.
You can download the free trial here if you want to give it a try.
Disclaimer: I own SpreadsheetGear LLC