A few weeks back I read in VSJ magazine that Oracle was coming out with Oracle Developer Tools for Oracle 10g database which would sort of enable use of .net framework in Oracle.
I logged into OTN and I had a sniff around. Over the last few years MSDE which is the stripped down SQL Desktop Engine has gained a lot of support and market because even though it's limited functionality, it still can do lot of shit. The new version of SQL Server is also coming out with new MSDE christined SQL Server 2005 Express Edition. What I saw on OTN surprised me. Oracle wants a piece of it too.
The release 2 supports .net framework 1.0 and above and you can write stored procedures and probably functions using .net. It creates PL/SQL wrappers for the .net code and when called it loads CLR as a seperate process and uses LPC to communicate with CLR. That would sort of do the job but maybe take a little longer. The fact that thats all you can do with .net is the limiting factor.
Even IBM who I consider proponents of Java support .net framework 1.1 in there DB2 UDB 8.2 or something like that. They like Oracle allow only Stored Proc and UDFs using .net languages. The CLR is again hosted in a seperate process.
I think SQL 2005 has the most extensive implementation out there supporting, Stored Procs, UDFs, UDTs, Triggers etc.