sql增删改查封装

App.config文件

1 <?xml version="1.0" encoding="utf-8" ?>
2 <configuration>
3     <startup>
4         <supportedRuntime version="v4.0" sku=".NETFramework,Version=v4.5" />
5     </startup>
6   <connectionStrings>
7     <add connectionString="Data Source = .; Initial Catalog = mysql; Integrated Security = True;" name="conStr" />
8   </connectionStrings>
9 </configuration>

sqlHelper封装类库代码

 1 using System;
 2 using System.Collections.Generic;
 3 using System.Linq;
 4 using System.Text;
 5 using System.Threading.Tasks;
 6 //新建一个App.confit文件，引用下面两个命名空间
 7 using System.Configuration;
 8 using System.Data.SqlClient;
 9
10 namespace 封装
11 {
12     public class SqlHelper
13     {
14         //读取连接字符串
15         private static readonly string str = ConfigurationManager.ConnectionStrings["conStr"].ConnectionString;
16         //三个方法，关键是第三个方法，查询，条件判断比较多
17         /// <summary>
18         /// 此方法可以做增删改
19         /// </summary>
20         /// <param name="sql">sql语句</param>
21         /// <param name="ps">sql语句中的参数</param>
22         /// <returns>返回受影响的行数，int类型</returns>
23         private static int ExecuteNonQuery(string sql, params SqlParameter[] ps)
24         {
25             using (SqlConnection con = new SqlConnection(str))
26             {
27                 using (SqlCommand cmd = new SqlCommand(sql, con))
28                 {
29                     con.Open();
30                     if (ps != null)
31                     {
32                         cmd.Parameters.AddRange(ps);
33                     }
34
35                     return cmd.ExecuteNonQuery();
36                 }
37             }
38         }
39         /// <summary>
40         /// 该方法用在查询上
41         /// </summary>
42         /// <param name="sql">sql语句</param>
43         /// <param name="ps">sql语句中的参数</param>
44         /// <returns>返回首行首列，object类型</returns>
45         private static object ExecuteScalar(string sql, params SqlParameter[] ps)
46         {
47             using (SqlConnection con = new SqlConnection(str))
48             {
49                 using (SqlCommand cmd = new SqlCommand(sql, con))
50                 {
51                     con.Open();
52                     if (ps != null)
53                     {
54                         cmd.Parameters.AddRange(ps);
55                     }
56                     return cmd.ExecuteScalar();
57                 }
58             }
59         }
60         /// <summary>
61         /// 该方法用于查询，读数据
62         /// </summary>
63         /// <param name="sql">sql语句</param>
64         /// <param name="ps">sql语句中的参数</param>
65         /// <returns>返回sqldatareader对象，里面有数据</returns>
66         private static SqlDataReader ExecuteReader(string sql, params SqlParameter[] ps)
67         {
68             //这地方不用using，因为不知道什么时候释放
69             SqlConnection con = new SqlConnection(str);
70             using (SqlCommand cmd = new SqlCommand(sql,con))
71             {
72                 if (ps!=null)
73                 {
74                     cmd.Parameters.AddRange(ps);
75                 }
76                 try
77                 {
78                     con.Open();
79                     //这个重载会datareader关闭时，自动关闭connection
80                     return cmd.ExecuteReader(System.Data.CommandBehavior.CloseConnection);
81                 }
82                 catch (Exception ex)
83                 {
84                     con.Close();
85                     con.Dispose();
86                     throw ex;
87                 }
88             }
89         }
90     }
91 }