数据库连接LinqHelper

一个关于linq的操作类
  1 /// <summary>
  2      /// Linq通用数据访问类
  3      /// 指定TDataBase来代替后面要使用的数据上下文(指代)
  4      /// where：说明指代的类型
  5      /// new：限定必须有一个不带参数的构造函数
  6      /// </summary>
  7      /// <typeparam name="TDataBase"></typeparam>
  8      public class LinqHelper<TDataBase> where TDataBase : DataContext, new()
  9      {
 10          private static string connectionString = ConfigurationManager.ConnectionStrings["ConnectionString"].ToString();
 11          TDataBase db = null;
 12          /// <summary>
 13          /// 创建数据库连接
 14          /// </summary>
 15          public LinqHelper()
 16          {
 17              db = new TDataBase();
 18              db.Connection.ConnectionString = connectionString;
 19          }
 20  
 21          /// <summary>
 22          /// 获取所有数据
 23          /// </summary>
 24          /// <typeparam name="T"></typeparam>
 25          /// <returns></returns>
 26          public List<T> GetList<T>() where T : class
 27          {
 28              return db.GetTable<T>().ToList();
 29          }
 30  
 31          /// <summary>
 32          /// 按条件查询
 33          /// </summary>
 34          /// <typeparam name="T"></typeparam>
 35          /// <param name="predicate">Lambda表达式</param>
 36          /// <returns></returns>
 37          public List<T> GetList<T>(Expression<Func<T, bool>> predicate) where T : class
 38          {
 39              return db.GetTable<T>().Where(predicate).ToList();
 40          }
 41  
 42          /// <summary>
 43          /// 获取实体
 44          /// </summary>
 45          /// <typeparam name="T"></typeparam>
 46          /// <param name="predicate"></param>
 47          /// <returns></returns>
 48          public T GetEntity<T>(Expression<Func<T, bool>> predicate) where T : class
 49          {
 50              return db.GetTable<T>().Where(predicate).FirstOrDefault();
 51          }
 52  
 53          /// <summary>
 54          /// 添加实体
 55          /// </summary>
 56          /// <typeparam name="T"></typeparam>
 57          /// <param name="entity"></param>
 58          public void InsertEntity<T>(T entity) where T : class
 59          {
 60              try
 61              {
 62                  //将对象保存到上下文当中
 63                  db.GetTable<T>().InsertOnSubmit(entity);
 64                  //提交更改
 65                  db.SubmitChanges();
 66              }
 67              catch (Exception ex)
 68              {
 69                  throw new Exception(ex.Message);
 70              }
 71          }
 72  
 73          /// <summary>
 74          /// 修改实体
 75          /// </summary>
 76          /// <typeparam name="T"></typeparam>
 77          /// <param name="entity"></param>
 78          public void UpdateEntity<T>(T entity) where T : class
 79          {
 80              try
 81              {
 82                  //将新实体附加到上下文
 83                  db.GetTable<T>().Attach(entity);
 84                  //刷新数据库
 85                  db.Refresh(RefreshMode.KeepCurrentValues, entity);
 86                  //提交更改
 87                  db.SubmitChanges(ConflictMode.ContinueOnConflict);
 88              }
 89              catch (Exception ex)
 90              {
 91                  throw new Exception(ex.Message);
 92              }
 93          }
 94  
 95          /// <summary>
 96          /// 删除实体
 97          /// </summary>
 98          /// <typeparam name="T"></typeparam>
 99          /// <param name="predicate"></param>
100          public void DeleteEntity<T>(Expression<Func<T, bool>> predicate) where T : class
101          {
102              try
103              {
104                  //获取要删除的实体
105                  var entity = db.GetTable<T>().Where(predicate).FirstOrDefault();
106                  if (entity == null) return;
107                  db.GetTable<T>().DeleteOnSubmit(entity);
108                  db.SubmitChanges(ConflictMode.ContinueOnConflict);
109              }
110              catch (Exception ex)
111              {
112                  throw new Exception(ex.Message);
113              }
114          }
115      }
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