Beginning Microsoft SQL Server 2008 ... - S3 Tech Training

Appendix B: Very Simple Connectivity Examples
Within the ADO.NET example, we’ll look at a couple of different approaches to how to utilize the features
provided.
All code examples provided here were created with Visual Studio 2008. The basic
principles provided here should work just fine under other versions of Visual Studio
or other editors for the languages provided, but it’s conceivable that I’ve thrown in a
.NET Framework 3.5 quirk and not noticed it. (If so, apologies to those operating
under different .NET Framework versions.)
Some General Concepts
Before we get going too deep with “just code,” there are a few key constructs that we need to understand.
There are several different connectivity models that have come and gone over time; you’ll hear
about such names as OLE-DB, ODBC, and, of course, ADO, among others. The connectivity model of the
day these days tends to be ADO.NET or LINQ. Given the life span of these things, I wouldn’t be surprised
at all if there were yet a different one by the time the next version of SQL Server comes out.
Even with all the different models that have come and gone, some concepts seem to always exist in
every object model — let’s take a look at these real quick:
❑ Connection: The connection object is pretty much what it sounds like — the object that defines
and establishes your actual communications link to your database. The kinds of parameter information
that will exist for a connection object include such things as the username, password,
database, and server you wish to connect to. Some of the methods that will exist include such
things as connect and disconnect.
❑ Command: This object is the one that carries information about what it is you want to do. Some
object models will not include this object, or at least not feature it, but the concept is always there.
(It is sometimes hidden as a method of the connection object.)
❑ Data set: This is the result of a query — that is, if the query returns data. Some queries in which
you execute, for example, a simple INSERT statement, will not return results, but, if results are
returned, there will be some sort of data set (sometimes called a result set or recordset) that the
query returns them into. Data set objects will generally allow for you to iterate through the
records in them (often forward only in direction but usually settable to allow for more robust
positioning). They will also generally allow for data to be updated, inserted, and deleted.
Connectivity Examples
650
What we’re going to do in this section is provide some hyper (and I do mean in the extreme) examples of
how to get connected in the two most common languages of the day — C# and VB.NET. For each language,
we’ll show a couple of examples — one for each of two different kinds of operations (fetching a simple
data set and executing a query that does not return a data set).