SplendidCRM was written in C# using the Microsoft .NET Framework 2.0 and Microsoft SQL Server 2000.
SplendidCRM supports the following features:
There is a free ASP.NET Open Source Version and a "Pro" version for ISVs, etc.
Check it out at http://www.splendidcrm.com/
The NEW 2.0 version is in Beta and will probably be released by the end of next month.