SqlConnection
The C# SqlConnection
class
handles database connections. It initiates a connection to your SQL database. This class
is best used in a using resource acquisition statement.
We call Open to query the database with SqlCommand
. With System.Data.SqlClient
classes, we often use many together (like SqlParameter
, SqlDataReader
).
We use SqlConnection
in a "using" statement. The SqlConnection
has a constructor that requires a string
reference pointing to the connection string character data.
SqlConnection
code before you can perform a database query.using System; using System.Data.SqlClient; class Program { static void Main() { // // First access the connection string. // string connectionString = ConsoleApplication1.Properties.Settings.Default.ConnectionString; // // In a using statement, acquire the SqlConnection as a resource. // using (SqlConnection con = new SqlConnection(connectionString)) { // // Open the SqlConnection. // con.Open(); // // This code uses an SqlCommand based on the SqlConnection. // using (SqlCommand command = new SqlCommand("SELECT TOP 2 * FROM Dogs1", con)) using (SqlDataReader reader = command.ExecuteReader()) { while (reader.Read()) { Console.WriteLine("{0} {1} {2}", reader.GetInt32(0), reader.GetString(1), reader.GetString(2)); } } } } }57 Koko Shar Pei 130 Fido Bullmastiff
Program
notesThis program will not work unless you change the connection string reference to point to a correct one in your environment.
The using statement creates a read-only variable of type SqlConnection
. You need to call Open()
on the SqlConnection
instance before using it in an SqlCommand
.
SqlConnection
is passed as the parameter to the SqlCommand
. In this way we specify that the SqlCommand
"uses" the SqlConnection
.We looked at database code. We stressed the proper usage of the SqlConnection
class
and the resource acquisition pattern.