Enough theory! Let's write some code and see how this works. Working with ADO.NET can be complex, but for many queries, the model is surprisingly simple. In this example, you'll create a console application and list out bits of information from the
Customers table in the Northwind database.
Create a new console application (we'll go back to console applications to keep things simple here). When the application opens, add the following two
using statements to the top:
using System.Data; using System.Data.SqlClient;
The first thing you're going to need in the program itself is a way to identify the location of the SQL Server instance to your program. This is commonly called the connection string. It's a simple enough string format, and once you've defined it, you can use the same string anytime you want to access Northwind. If you're using SQL Server Express, as installed with C# Express in Chapter 1, the access path is simple:
.\sqlexpress. However, because you're defining a string, you need to escape the slash character, as we discussed in Chapter 15 (or you could also use a literal string). Create the connection string like this (all on one line):
string connectionString = "server=.\\sqlexpress; Trusted_Connection=yes;database=Northwind";
The next thing you need is a string to hold the SQL command itself. SQL Server can't understand C# directly, so you can't treat the entries in the database as though they were C# objects. (It'd be nice if you could, though, ...