1 static class SqlHelper 2     { 3         //app.config文件的继承： 4  5         public static readonly string connstr =  6             ConfigurationManager.ConnectionStrings["connstr"].ConnectionString; 7  8         public static int ExecuteNonQuery(string sql,  9             params SqlParameter[] parameters)10         {11             using (SqlConnection conn = new SqlConnection(connstr))12             {13                 conn.Open();14                 using (SqlCommand cmd = conn.CreateCommand())15                 {16                     cmd.CommandText = sql;17                     cmd.Parameters.AddRange(parameters);18                     return cmd.ExecuteNonQuery();19                 }20             }21         }22 23         public static object ExecuteScalar(string sql,24             params SqlParameter[] parameters)25         {26             using (SqlConnection conn = new SqlConnection(connstr))27             {28                 conn.Open();29                 using (SqlCommand cmd = conn.CreateCommand())30                 {31                     cmd.CommandText = sql;32                     cmd.Parameters.AddRange(parameters);33                     return cmd.ExecuteScalar();34                 }35             }36         }37 38         public static DataTable ExecuteDataTable(string sql,39             params SqlParameter[] parameters)40         {41             using (SqlConnection conn = new SqlConnection(connstr))42             {43                 conn.Open();44                 using (SqlCommand cmd = conn.CreateCommand())45                 {46                     cmd.CommandText = sql;47                     cmd.Parameters.AddRange(parameters);48 49                     DataSet dataset = new DataSet();50                     SqlDataAdapter adapter = new SqlDataAdapter(cmd);51                     adapter.Fill(dataset);52                     return dataset.Tables[0];53                 }54             }55         }56 57         /// <summary>58         /// 从数据库读取字段时，防止nul值报错59         /// </summary>60         /// <param name="value"></param>61         /// <returns></returns>62         public static object FromDbValue(object value)63         {64             if (value =http://www.mamicode.com/= DBNull.Value)65             {66                 return null;67             }68             else69             {70                 return value;71             }72         }73 74         /// <summary>75         /// 写入数据库字段值时，防止Null值报错76         /// </summary>77         /// <param name="value"></param>78         /// <returns></returns>79         public static object ToDbValue(object value)80         {81             if (value =http://www.mamicode.com/= null)82             {83                 return DBNull.Value;84             }85             else86             {87                 return value;88             }89         }90     }