最近做移動的專案，要求底層資料庫是Oracle，但是因為本機是Sqlserver的環境。想了下，於是使用Entity Framework 進行開發，在開發完成以後切換到Oracle環境。想了下，就決定把以前封裝的Linq的底層操作類進行了修改，形成EF的底層操作類。這樣在自己熟悉的環境下，效率也會高很多，及時以後這個不好用，我切換起來也會簡單很多。多的不過了，各位看官上程式碼，首先上的第一個類是底層操作的類。

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Linq.Expressions;
using System.Data.Entity;
using NOAS.PublicOpinionMonitor.ENTITY;
using System.Data.Linq;
using System.Data.Objects;
using System.Reflection;
using System.Threading;

namespace NOAS.PublicOpinionMonitor.Access.Common
{
    public class DataCommon
    {
        static readonly string Connection = "name=POMonitorDBEntities";
        POMonitorDBEntities entities = new ENTITY.POMonitorDBEntities(Connection);

        #region 根據SQL語句查詢資料
        public IEnumerable<T> ExecuteQuery<T>(string conn, string query, params object[] parms)
        {
            try
            {
                if (string.IsNullOrEmpty(conn))
                {
                    return entities.ExecuteStoreQuery<T>(query, parms);
                }
                else
                {
                    DataContext myDC = new DataContext(conn);
                    return myDC.ExecuteQuery<T>(query, parms);
                }
            }
            catch (Exception ex) 
            {
                throw new Exception(ex.Message);
            }
        }
        public IEnumerable<T> ExecuteQuery<T>(string query)
        {
            return ExecuteQuery<T>(string.Empty, query, new object[] { });
        }
        #endregion

        #region 執行操作型別SQl語句
        /// <summary>
        /// 執行SQL命令
        /// </summary>
        /// <param name="sqlCommand"></param>
        /// <returns></returns>
        public int ExecuteSqlCommand(string sqlCommand, string connection = null)
        {
            if (string.IsNullOrEmpty(connection))
                return entities.ExecuteStoreCommand(sqlCommand); //ExecuteCommand(sqlCommand);
            else
            {
                POMonitorDBEntities entitiesNew = new POMonitorDBEntities(connection);
                return entitiesNew.ExecuteStoreCommand(sqlCommand);
            }
        }
        /// <summary>
        /// 執行SQL命令
        /// </summary>
        /// <param name="sqlCommand"></param>
        /// <returns></returns>
        public void ExecuteSqlCommand(string sqlCommand)
        {
            ExecuteSqlCommand(connection: string.Empty, sqlCommand: sqlCommand);
        }
        #endregion


        #region 私有方法
        private ObjectSet<T> GetTable<T>() where T : class
        {
            try
            {
                ObjectSet<T> customers = entities.CreateObjectSet<T>();
                return customers;
            }
            catch (Exception ex)
            {
                throw ex;
            }

        }
        #endregion

        #region 統計指定條件的資料量
        /// <summary>
        /// 統計指定條件的資料量
        /// </summary>
        /// <typeparam name="T"></typeparam>
        /// <param name="query"></param>
        /// <returns></returns>
        public virtual int Count<T>(Expression<Func<T, bool>> query) where T : class
        {
            var table = GetTable<T>();
            return (from t in table
                    select t).Where(query).Count();
        }
        #endregion


        #region 獲取單個實體
        /// <summary>
        /// 獲取單個實體
        /// </summary>
        /// <typeparam name="T">泛型型別引數</typeparam>
        /// <param name="express">查詢條件</param>
        /// <returns></returns>
        public virtual T GetSingleEntity<T>(Expression<Func<T, bool>> query) where T : class
        {
            try
            {
                var table = GetTable<T>();
                return (from t in table
                        select t).Where(query).SingleOrDefault();
            }
            catch (Exception ex)
            {
                throw ex;
            }
        }
        #endregion


        #region 更新實體
        /// <summary>
        /// 更新實體
        /// </summary>
        /// <typeparam name="T">泛型型別引數</typeparam>
        /// <param name="entity">更改後的實體</param>
        public virtual bool Update<T>(T entity) where T : class
        {
            object propertyValue = null;
            T entityFromDB = GetSingleEntity<T>(s => s == entity);
            if (null == entityFromDB)
                return false;
            PropertyInfo[] properties = entityFromDB.GetType().GetProperties();
            foreach (PropertyInfo property in properties)
            {
                propertyValue = null;
                if (null != property.GetSetMethod())
                {
                    PropertyInfo entityProperty =
                          entity.GetType().GetProperty(property.Name);
                    if (entityProperty.PropertyType.BaseType ==
                        Type.GetType("System.ValueType") ||
                        entityProperty.PropertyType ==
                        Type.GetType("System.String"))

                        propertyValue = entity.GetType().GetProperty(property.Name).GetValue(entity, null);
                    if (propertyValue == null)
                    {
                        Thread.Sleep(50);
                        propertyValue = entity.GetType().GetProperty(property.Name).GetValue(entity, null);
                    }
                    if (null != propertyValue)
                        property.SetValue(entityFromDB, propertyValue, null);
                }
            }

            entities.SaveChanges();
            return true;
        }

        #endregion


        #region 獲取相關的實體資訊
        /// <summary>
        /// 分頁_獲取指定頁的資料集合
        /// </summary>
        /// <typeparam name="T">泛型型別引數</typeparam>
        /// <param name="query">查詢條件</param>
        /// <param name="pageSize">每頁顯示數量</param>
        /// <param name="pageNum">當前頁號</param>
        /// <param name="pageTotal">總頁數</param>
        /// <param name="datasTotal">總資料量</param>
        /// <returns></returns>
        public virtual List<T> GetAllEntity<T>(Expression<Func<T, bool>> query, int pageSize, int pageNum, out int pageTotal, out int datasTotal) where T : class
        {
            var table = GetTable<T>();

            datasTotal = (from t in table
                          select t).Where(query).Count();

            pageTotal = datasTotal / pageSize + 1;

            return (from t in table
                    select t).Where(query).Skip(pageSize * (pageNum - 1)).Take(pageSize).ToList();
        }
        /// <summary>
        /// 分頁_獲取指定頁的資料集合
        /// </summary>
        /// <typeparam name="T">泛型型別引數</typeparam>
        /// <param name="query">查詢條件</param>
        /// <param name="pageSize">每頁顯示數量</param>
        /// <param name="pageNum">當前頁號</param>
        /// <param name="pageTotal">總頁數</param>
        /// <param name="datasTotal">總資料量</param>
        /// <returns></returns>
        public virtual List<T> GetAllEntity<T>(Expression<Func<T, bool>> query, Func<T, object> orderByDesc, int pageSize, int pageNum, out int pageTotal, out int datasTotal) where T : class
        {
            var table = GetTable<T>();

            datasTotal = (from t in table
                          select t).Where(query).Count();

            pageTotal = (int)Math.Ceiling((double)datasTotal / pageSize);
            return (from t in table
                    select t).Where(query).OrderByDescending(orderByDesc).Skip(pageSize * (pageNum - 1)).Take(pageSize).ToList();
        }
        /// <summary>
        /// 獲取指定條件的實體集合

        /// </summary>
        /// <typeparam name="T">泛型型別引數</typeparam>
        /// <param name="query">查詢條件</param>
        /// <returns></returns>
        public virtual List<T> GetAllEntity<T>(Expression<Func<T, bool>> query) where T : class
        {
            var table = GetTable<T>();
            return (from t in table
                    select t).Where(query).ToList();
        }

        /// <summary>
        /// 獲取指定條件的實體集合

        /// </summary>
        /// <typeparam name="T">泛型型別引數</typeparam>
        /// <param name="query">查詢條件</param>      
        /// <param name="orderAsc"></param>       
        /// <returns></returns>
        public virtual List<T> GetAllEntity<T>(Expression<Func<T, bool>> query, bool isAsc, Func<T, object> order) where T : class
        {
            var table = GetTable<T>();
            if (isAsc)
                return (from t in table
                        select t).Where(query).OrderBy(order).ToList();
            return (from t in table
                    select t).Where(query).OrderByDescending(order).ToList();
        }

        public virtual List<T> GetAllEntity<T>() where T : class
        {
            var table = GetTable<T>();
            return (from t in table
                    select t).ToList();
        }
        #endregion


        #region 新增實體
        /// <summary>
        /// 新增單個實體
        /// </summary>
        /// <typeparam name="T">泛型型別引數</typeparam>
        /// <param name="entity">待插入的實體</param>
        /// <returns></returns>
        public virtual void InsertEntity<T>(T entity) where T : class
        {
            var table = GetTable<T>();
            table.AddObject(entity);
            entities.SaveChanges();
        }

        /// <summary>
        /// 批量新增實體
        /// </summary>
        /// <typeparam name="T">泛型型別引數</typeparam>
        /// <param name="entityList">待新增的實體集合</param>
        /// <returns></returns>
        public virtual void BatchInsertEntity<T>(List<T> entityList) where T : class
        {
            if (entityList.Count > 0)
            {
                var table = GetTable<T>();
                foreach (var item in entityList)
                {
                    table.AddObject(item);//DeleteAllOnSubmit(toDeletedColl);
                }
                entities.SaveChanges();
            }
        }
        #endregion

        #region 刪除實體
        /// <summary>
        /// 根據條件刪除指定實體
        /// </summary>
        /// <typeparam name="T">實體</typeparam>
        /// <param name="query">條件</param>
        /// <returns>bool</returns>
        public virtual void DeleteEntitys<T>(Expression<Func<T, bool>> query) where T : class
        {
            var table = GetTable<T>();
            var toDeletedColl = table.Where(query);
            if (toDeletedColl != null && toDeletedColl.Count() > 0)
            {
                foreach (var item in toDeletedColl)
                {
                    table.DeleteObject(item);//DeleteAllOnSubmit(toDeletedColl);
                }
                entities.SaveChanges();
            }
        }
        #endregion
    }
}