public abstract class DbConnection : Component, 
    IDbConnection, IDisposable

 1 using System;
 2 using System.Collections.Generic;
 3 using System.Linq;
 4 using System.Text;
 5 using System.Data;
 6 using System.Data.SqlClient;
 7 
 8 namespace Connection
 9 {
10     class Program
11     {
12         static void Main(string[] args)
13         {
14             //構(gòu)造連接字符串
15             SqlConnectionStringBuilder connStr = new SqlConnectionStringBuilder();
16             connStr.DataSource = @".\SQLEXPRESS";
17             connStr.InitialCatalog = "master";
18             connStr.IntegratedSecurity = true;
19 
20             SqlConnection conn = new SqlConnection();//創(chuàng)建連接對象
21             conn.ConnectionString = connStr.ConnectionString;//設(shè)置連接字符串
22 
23             conn.Open();//打開連接
24 
25             if(conn.State == ConnectionState.Open)
26             {
27                 Console.WriteLine("Database is linked.");
28                 Console.WriteLine("\nDataSource:{0}",conn.DataSource);
29                 Console.WriteLine("Database:{0}",conn.Database);
30                 Console.WriteLine("ConnectionTimeOut:{0}",conn.ConnectionTimeout);
31             }
32 
33             conn.Close();//關(guān)閉連接
34             conn.Dispose();//釋放資源
35 
36             if(conn.State == ConnectionState.Closed)
37             {
38                 Console.WriteLine("\nDatabase is closed.");
39             }
40 
41             Console.Read();
42         }
43     }
44 }

 1 SqlConnection conn = new SqlConnection(connStr);
 2 try
 3 {
 4       conn.Open();
 5 }
 6 catch(Exception ex)
 7 {
 8           ;//todo
 9 }
10 finially
11 {
12      conn.Close();
13 }

1 using(SqlConnection conn = new SqlConnection(connStr))
2 {
3      ;//todo
4 }