using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Data;
using System.Data.SqlClient;
using System.Windows.Forms;
 1 public class DBHelper
 2     {
 3         static string connStr = "Workstation id = localhost;" +
 4                                "Integrated Security = SSPI;" + 
 5                                 "Database = 数据库名字;";//填入SQL数据库的登录信息。
 6 
 7        
 8         static SqlConnection conn = new SqlConnection(connStr);
 9 
10         public static SqlDataReader GetDataReader(string sql)//返回值是一个数组，可通过dr[0],dr[1]使用各字段的值
11         {
12             SqlConnection myConn = conn;
13             SqlDataReader dr = null;
14 
15             try
16             {
17                 if (myConn.State == ConnectionState.Closed)
18                 {
19                     myConn.Open();
20                 }
21                 SqlCommand cmd = new SqlCommand(sql, myConn);
22                
23                 dr = cmd.ExecuteReader(CommandBehavior.CloseConnection);
24             }
25             catch 
26             {
27                 
28                 if (myConn.State == ConnectionState.Open)
29                 {
30                     myConn.Close();
31                 }
32 
33             }
34             return dr;
35         }
36 
37         public static bool ExecuteNonQuery(string sql)  //对于 UPDATE、INSERT 和 DELETE 语句，返回值为该命令所影响的行数。对于所有其他类型的语句，返回值为 -1。如果发生回滚，返回值也为 -1
38         {
39             int n = 0;
40 
41             try
42             {
43                 if (conn.State == ConnectionState.Closed)
44                 {
45                     conn.Open();
46                 }
47                 SqlCommand cmd = new SqlCommand(sql, conn);
48                 n = cmd.ExecuteNonQuery();
49                 
50             }
51             catch
52             {
53                 
54                 return false;
55             }
56             finally
57             {
58                 if (conn.State == ConnectionState.Open)
59                 {
60                     conn.Close();
61                 }
62             }
63             return n > 0;
64         }
65 
66         public static Object ExecuteScalar(string sql)//使用ExecuteScalar()，增删改查如果成功，会返回一个对象，否则会返回一个null；
67         {
68             Object ob = null;
69 
70             try
71             {
72                 if (conn.State == ConnectionState.Closed)
73                 {
74                     conn.Open();
75                 }
76                 SqlCommand cmd = new SqlCommand(sql, conn);
77                 ob = cmd.ExecuteScalar();
78             }
79             catch
80             {
81                 return null;
82             }
83             finally
84             {
85                 if (conn.State == ConnectionState.Open)
86                 {
87                     conn.Close();
88                 }
89             }
90             return ob;
91         }
92     }
93 }