This white paper discusses how managed code can use ADO.NET when running inside SQL Server 2005 using the new SQLCLR feature.

SQL Server 2005 is highly integrated with the .NET Framework, enabling the creation of stored procedures, functions, user-defined types, and user-defined aggregates using your favorite .NET programming language. All of these constructs can take advantage of large portions of the .NET Framework infrastructure, the base class library, and third-party managed libraries.
In many cases the functionality of these pieces of managed code will be very computation-oriented. Things such as string parsing or scientific math are quite common in the applications that our early adopters are creating using SQLCLR.

However, you can do only so much using only number crunching and string manipulation algorithms in isolation. At some point you'll have to obtain your input or return results. If that information is relatively small and granular you can use input and output parameters or return values, but if you're handling a large volume of information, then in-memory structures won't be an appropriate representation/transfer mechanism; a database might be a better fit in those scenarios. If you choose to store the information in a database, then SQLCLR and a data-access infrastructure are the tools you'll need.

There are a number of scenarios where you'll need database access when running inside SQLCLR. One is the scenario I just mentioned, where you have to perform some computation over a potentially large set of data. The other is integration across systems, where you need to talk to different servers to obtain an intermediate answer in order to proceed with a database-related operation.

Now, if you're writing managed code and you want to do data access, what you need is ADO.NET.

Getting Started with ADO.NET Inside SQLCLR
The good news is that ADO.NET "just works" inside SQLCLR, so in order to get started you can leverage all your existing knowledge of ADO.NET.

To illustrate this take a look at the code snippet below. It would work fine in a client-side application, Web application, or a middle-tier component; it turns out that it will also work just fine inside SQLCLR.