关于ClownFish的问题

1.下面是我获取实体集合的方法 , 

        public IList<Model.Employee> GetList(int pageindex, string name, out int recCount)
        {
            var parameters = new
            {
                EmpName = name,
                PageIndex = 1,
                PageSize = 15,
                TotalRecords = 0
            };

            string sql = @"
;WITH  MyList
AS ( SELECT row_number() OVER ( ORDER BY p.AddDate ASC ) AS rownumber ,p.*
    FROM  dbo.[Employee] p
    WHERE len(@EmpName)=0 or p.EmpName like '%'+ @EmpName +'%'
    )
SELECT  rownumber , *
FROM    MyList
WHERE   rownumber >= ( @pageindex - 1 ) * @pagesize + 1
        AND rownumber <= ( @pageindex - 1 ) * @pagesize
        + ( @pagesize );

select @TotalRecords=count(*) FROM dbo.[Employee] p
WHERE  len(@EmpName)=0 or p.EmpName like '%'+ @EmpName +'%'
";
            using (DbContext dbContext = new DbContext(false))
            {
                dbContext.CreateCommand(sql, CommandType.Text);
                dbContext.SetCommandParameters(parameters);
                dbContext.AddParameter("TotalRecords", 0, DbType.Int32, 4, ParameterDirection.Output);

                List<Model.Employee> list = dbContext.FillList<Model.Employee>();
                recCount = parameters.TotalRecords;
                return list;
            }
        }

结果发生了这个异常 , 不知为何?

　　

2.下面这个是我的实体:

   public class Employee
    {
        public Employee()
        {

        }

        private Int32 _EmpId;
        /// <summary>
        /// 用户ID
        /// </summary>	
        public Int32 EmpId
        {
            get { return _EmpId; }
            set { _EmpId = value; }
        }

        ...........

        private string _EmpName;
        /// <summary>
        /// 用户名称
        /// </summary>	
        public string EmpName
        {
            get { return _EmpName; }
            set { _EmpName = value; }
        }
        private DateTime? _Birthday;
        /// <summary>
        /// 生日
        /// </summary>	
        public DateTime? Birthday
        {
            get { return _Birthday; }
            set { _Birthday = value; }
        }
        private DateTime _AddDate;
        /// <summary>
        /// 录入时间
        /// </summary>	
        public DateTime AddDate
        {
            get { return _AddDate; }
            set { _AddDate = value; }
        }
    }  

　　下面是我新增Employee的方法

 public override int Add(Model.Employee model)
        {
            string sql = @"
insert into [Employee] ([LoginId],[EmpName],[EmpPwd],[IdNumber],[Telephone],[Fixphone],[Birthday],[Sex],[JobName],[EmpState],[DistName],[OrderQuota],[ShipQuota],[JoinDate],[BizType],[Roles])
values (@LoginId,@EmpName,@EmpPwd,@IdNumber,@Telephone,@Fixphone,@Birthday,@Sex,@JobName,@EmpState,@DistName,@OrderQuota,@ShipQuota,@JoinDate,@BizType,'');
select scope_identity();";
 
            using (DbContext dbContext = new DbContext(true))
            {
                model.EmpId = DbHelper.ExecuteScalar<int>(sql, model, dbContext, CommandKind.SqlTextWithParams);
                dbContext.CommitTransaction();
            }
 
            return model.EmpId;
        }

　　Birthday此时是null值, 即该员工未填写生日 , 执行Add方法时结果出现以下错误:

       以下是SqlProfiler捕获的信息:

大家知道是什么问题吗??