[C#] 简单的 Helper 封装 -- SQLiteHelper-白红宇

[C#] 简单的 Helper 封装 -- SQLiteHelper

阅读量：4972 次

发布时间：2019-06-12

本文共 3034 字，大约阅读时间需要 10 分钟。

1 using System;  2 using System.Data;  3 using System.Data.SQLite;  4   5 namespace SqliteConsoleApp  6 {  7     ///   8     /// SQLite 助手  9     /// 
 10     public sealed class SQLiteHelper 11     { 12         private const string ConnectionStr = "Data Source=recipes.s3db"; 13         private static SQLiteHelper _instance; 14         private static readonly object Locker = new object (); 15  16         private SQLiteHelper() 17         { 18         } 19  20         ///  21         /// 获取实例 22         /// 
 23         /// 
      24         public static SQLiteHelper GetInstance() 25         { 26             if (_instance == null ) 27             { 28                 lock (Locker) 29                 { 30                     if (_instance == null ) 31                     { 32                         _instance = new SQLiteHelper (); 33                     } 34                 } 35             } 36  37             return _instance; 38         } 39  40         ///  41         /// 获取数据表 42         /// 
 43         ///  需要执行的命令文本  44         /// 
     
       一个数据表集合 
      45         public DataTable GetDataTable( string cmdText) 46         { 47             var dt = new DataTable(); 48  49             try 50             { 51                 using (var conn = new SQLiteConnection (ConnectionStr)) 52                 { 53                     conn.Open(); 54                     var cmd = new SQLiteCommand(conn) {CommandText = cmdText}; 55                     using (var reader = cmd.ExecuteReader()) 56                     { 57                         dt.Load(reader); 58                     } 59                 } 60             } 61             catch (Exception e) 62             { 63                 throw new Exception(e.Message); 64             } 65  66             return dt; 67         } 68  69         ///  70         /// 执行非查询命令 71         /// 
 72         ///  需要执行的命令文本  73         /// 
     
       返回更新的行数 
      74         public int ExecuteNonQuery( string cmdText) 75         { 76             using (var conn = new SQLiteConnection (ConnectionStr)) 77             { 78                 conn.Open(); 79                 var cmd = new SQLiteCommand(conn) {CommandText = cmdText}; 80                 var rowsUpdated = cmd.ExecuteNonQuery(); 81  82                 return rowsUpdated; 83             } 84         } 85  86         ///  87         /// 执行检索单项命令 88         /// 
 89         ///  需要执行的命令文本  90         /// 
     
       一个字符串 
      91         public string ExecuteScalar( string cmdText) 92         { 93             using (var conn = new SQLiteConnection (ConnectionStr)) 94             { 95                 conn.Open(); 96                 var cmd = new SQLiteCommand(conn) {CommandText = cmdText}; 97                 var value = cmd.ExecuteScalar(); 98  99                 if (value != null )100                 {101                     return value.ToString();102                 }103             }104 105             return "" ;106         }107     }108 }