1 using System;  2 using System.Collections.Generic;  3 using System.Linq;  4 using System.Text;  5 using System.Threading.Tasks;  6 using System.Data.SqlClient;  7 using System.Data;  8   9 namespace MySchool.DAL 10 { 11     public class DBHelper 12     { 13         //private const string conn = "Data Source=.;Initial Catalog=MySchool;User ID=GaoFei;Password=111111"; 14         private const string conn = "Data Source=.;Initial Catalog=MySchool;User ID=sa;Password=sa"; 15         private static SqlConnection connection = new SqlConnection(conn); 16  17  18         /// <summary> 19         /// 读取数据 20         /// </summary> 21         /// <returns></returns> 22         public static SqlDataReader Reader(string sql) 23         { 24             try 25             { 26                 connection.Open(); 27                 SqlCommand comm = new SqlCommand(sql, connection); 28                 return comm.ExecuteReader(CommandBehavior.CloseConnection); 29             } 30             catch (Exception ex) 31             { 32                 throw; 33             } 34         } 35  36         /// <summary> 37         /// 增删改数据 38         /// </summary> 39         /// <param name="sql"></param> 40         /// <returns></returns> 41         public static int ExecuteNonQuery(string sql) 42         { 43             try 44             { 45                 connection.Open();   //打开数据库连接 46                 SqlCommand comm = new SqlCommand(sql, connection); 47                 return comm.ExecuteNonQuery(); 48             } 49             catch (Exception ex) 50             { 51                 throw; 52             } 53             finally 54             { 55                 connection.Close(); 56             } 57         } 58         /// <summary> 59         /// 返回单个值 60         /// </summary> 61         /// <param name="sql"></param> 62         /// <returns></returns> 63         public static object ExecuteScalar(string sql) 64         { 65             try 66             { 67                 connection.Open();   //打开数据库连接 68                 SqlCommand comm = new SqlCommand(sql, connection); 69                 return comm.ExecuteScalar(); 70  71             } 72             catch (Exception) 73             { 74                 throw; 75             } 76             finally 77             { 78                 connection.Close(); 79             } 80         } 81         /// <summary> 82         /// 返回数据集 83         /// </summary> 84         /// <param name="sql"></param> 85         /// <param name="tableName"></param> 86         /// <returns></returns> 87         public static DataSet Fill(string sql, string tableName) 88         { 89             try 90             { 91                 connection.Open();  //打开连接 92                 //创建数据适配器对象 93                 SqlDataAdapter sda = new SqlDataAdapter(sql, connection); 94                 //创建数据集 95                 DataSet ds = new DataSet(); 96                 sda.Fill(ds, tableName); //填充数据集 97                 return ds; 98             } 99             catch (Exception ex)100             {101                 throw;102                 //将异常引发出现103                 //  throw new Exception(e.Message);104             }105             finally106             {107                 connection.Close();108             }109         }110     }111 }