use webrequest() function to send a web request,prepare a website using ASP.NET.
write some web service which access to SQL Server
the most easy way.
you can use NamePipe,communicate with your native program which can use ADO.NET.
same as ZeroMQ tech or WinSocket.
you can write a dll which contain a series method which can read/write SQL Server
if you have such a dll,remember share with us.