EF 保证线程内唯一 上下文的创建

using CZBK.HeiMaOA.Model;
using System;
using System.Collections.Generic;
using System.Data.Entity;
using System.Linq;
using System.Runtime.Remoting.Messaging;
using System.Text;
using System.Threading.Tasks;

namespace CZBK.HeiMaOA.DAL
{
   public class DBContextFactory
    {
       /// <summary>
       /// 保证在一次请求过程中只创建一次EF上下文实例.
       /// </summary>
       /// <returns></returns>
       public static DbContext CreateDbContext()
       {
           DbContext dbContext = (DbContext)CallContext.GetData("dbContext");
           if (dbContext == null)
           {
               dbContext = new OAEntities();
               CallContext.SetData("dbContext", dbContext);
           }
           return dbContext;
       }
    }
}

using CZBK.HeiMaOA.Model;
using System;
using System.Collections.Generic;
using System.Data.Entity;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace CZBK.HeiMaOA.DAL
{
  public  class BaseDal<T>where T:class,new()
    {
       // OAEntities Db = new OAEntities();
      DbContext Db = DBContextFactory.CreateDbContext();//完成EF上下文创建.
        /// <summary>
        /// 基本查询方法
        /// </summary>
        /// <param name="whereLambda"></param>
        /// <returns></returns>
        public IQueryable<T> LoadEntities(System.Linq.Expressions.Expression<Func<T, bool>> whereLambda)
        {
            return Db.Set<T>().Where<T>(whereLambda);
        }
        /// <summary>
        /// 分页方法
        /// </summary>
        /// <typeparam name="s">排序的约束</typeparam>
        /// <param name="pageIndex">当前页码</param>
        /// <param name="pageSize">每页显示记录数</param>
        /// <param name="totalCount">总条数</param>
        /// <param name="whereLambda">过滤条件</param>
        /// <param name="orderbyLambda">排序条件</param>
        /// <param name="isAsc">排序方式</param>
        /// <returns></returns>
        public IQueryable<T> LoadPageEntities<s>(int pageIndex, int pageSize, out int totalCount, System.Linq.Expressions.Expression<Func<T, bool>> whereLambda, System.Linq.Expressions.Expression<Func<T, s>> orderbyLambda, bool isAsc)
        {
            var temp = Db.Set<T>().Where<T>(whereLambda);
            totalCount = temp.Count();
            if (isAsc)//如果成立表示升序
            {
                temp = temp.OrderBy<T, s>(orderbyLambda).Skip<T>((pageIndex - 1) * pageSize).Take<T>(pageSize);
            }
            else
            {
                temp = temp.OrderByDescending<T, s>(orderbyLambda).Skip<T>((pageIndex - 1) * pageSize).Take<T>(pageSize);
            }
            return temp;

        }
        /// <summary>
        /// 删除数据
        /// </summary>
        /// <param name="entity"></param>
        /// <returns></returns>
        public bool DeleteEntity(T entity)
        {
            Db.Entry<T>(entity).State = System.Data.EntityState.Deleted;
         //   return Db.SaveChanges() > 0;
            return true;
        }
        /// <summary>
        /// 更新
        /// </summary>
        /// <param name="entity"></param>
        /// <returns></returns>
        public bool UpdateEntity(T entity)
        {
            Db.Entry<T>(entity).State = System.Data.EntityState.Modified;
           // return Db.SaveChanges() > 0;
            return true;
        }
        /// <summary>
        /// 添加数据
        /// </summary>
        /// <param name="entity"></param>
        /// <returns></returns>
        public T AddEntity(T entity)
        {
            Db.Set <T>().Add(entity);
            //Db.SaveChanges();
            return entity;
        }
    }
}