LinqHelper数据库连接代码

/// <summary>
     /// Linq通用数据访问类
     /// 指定TDataBase来代替后面要使用的数据上下文(指代)
     /// where：说明指代的类型
     /// new：限定必须有一个不带参数的构造函数
     /// </summary>
     /// <typeparam name="TDataBase"></typeparam>
     public class LinqHelper<TDataBase> where TDataBase : DataContext, new()
     {
         private static string connectionString = ConfigurationManager.ConnectionStrings["ConnectionString"].ToString();
         TDataBase db = null;
         /// <summary>
         /// 创建数据库连接
         /// </summary>
         public LinqHelper()
         {
             db = new TDataBase();
             db.Connection.ConnectionString = connectionString;
         }
 
         /// <summary>
         /// 获取所有数据
         /// </summary>
         /// <typeparam name="T"></typeparam>
         /// <returns></returns>
         public List<T> GetList<T>() where T : class
         {
             return db.GetTable<T>().ToList();
         }
 
         /// <summary>
         /// 按条件查询
         /// </summary>
         /// <typeparam name="T"></typeparam>
         /// <param name="predicate">Lambda表达式</param>
         /// <returns></returns>
         public List<T> GetList<T>(Expression<Func<T, bool>> predicate) where T : class
         {
             return db.GetTable<T>().Where(predicate).ToList();
         }
 
         /// <summary>
         /// 获取实体
         /// </summary>
         /// <typeparam name="T"></typeparam>
         /// <param name="predicate"></param>
         /// <returns></returns>
         public T GetEntity<T>(Expression<Func<T, bool>> predicate) where T : class
         {
             return db.GetTable<T>().Where(predicate).FirstOrDefault();
         }
 
         /// <summary>
         /// 添加实体
         /// </summary>
         /// <typeparam name="T"></typeparam>
         /// <param name="entity"></param>
         public void InsertEntity<T>(T entity) where T : class
         {
             try
             {
                 //将对象保存到上下文当中
                 db.GetTable<T>().InsertOnSubmit(entity);
                 //提交更改
                 db.SubmitChanges();
             }
             catch (Exception ex)
             {
                 throw new Exception(ex.Message);
             }
         }
 
         /// <summary>
         /// 修改实体
         /// </summary>
         /// <typeparam name="T"></typeparam>
         /// <param name="entity"></param>
         public void UpdateEntity<T>(T entity) where T : class
         {
             try
             {
                 //将新实体附加到上下文
                 db.GetTable<T>().Attach(entity);
                 //刷新数据库
                 db.Refresh(RefreshMode.KeepCurrentValues, entity);
                 //提交更改
                 db.SubmitChanges(ConflictMode.ContinueOnConflict);
             }
             catch (Exception ex)
             {
                 throw new Exception(ex.Message);
             }
         }
 
         /// <summary>
         /// 删除实体
         /// </summary>
         /// <typeparam name="T"></typeparam>
         /// <param name="predicate"></param>
         public void DeleteEntity<T>(Expression<Func<T, bool>> predicate) where T : class
         {
             try
             {
                 //获取要删除的实体
                 var entity = db.GetTable<T>().Where(predicate).FirstOrDefault();
                 if (entity == null) return;
                 db.GetTable<T>().DeleteOnSubmit(entity);
                 db.SubmitChanges(ConflictMode.ContinueOnConflict);
             }
             catch (Exception ex)
             {
                 throw new Exception(ex.Message);
             }
         }
     }