try/catch/finally

使用例子：

 1 public void ExecuteSql(string conString, string cmdString)
 2 {
 3 
 4     SqlConnection con = new SqlConnection(conString);
 5 
 6     try
 7 
 8     {
 9 
10         con.Open();
11 
12         SqlTransaction tran = con.BeginTransaction();
13 
14         SqlCommand cmd = new SqlCommand(cmdString, con);
15 
16         try
17 
18         {
19 
20             cmd.ExecuteNonQuery();
21 
22             tran.Commit();
23 
24         }
25 
26         catch (SqlException ex)
27 
28         {
29 
30             Console.WriteLine(ex.Message);
31 
32             //实现事务回滚
33 
34             tran.Rollback();
35 
36             throw new Exception("SQL Error!", ex);
37 
38         }
39 
40     }
41 
42     catch(Exception e)
43 
44     {
45 
46         throw (e);
47 
48     }
49 
50     finally   //无论是否抛出异常，程序都会执行finally,一般处理资源的释放等。
51 
52     {
53 
54         con.Close();
55 
56     }
57 }