linq增添数据 报 当 IDENTITY_INSERT 设置为 OFF 时，不能为表 'bx_wap_TypeInfo' 中的标识列插入显式值

当 IDENTITY_INSERT 设置为 OFF 时，不能为表 'bx_wap_TypeInfo' 中的标识列插入显式值。 
说明: 执行当前 Web 请求期间，出现未处理的异常。请检查堆栈跟踪信息，以了解有关该错误以及代码中导致错误的出处的详细信息。 

异常详细信息: System.Data.SqlClient.SqlException: 当 IDENTITY_INSERT 设置为 OFF 时，不能为表 'bx_wap_TypeInfo' 中的标识列插入显式值。

源错误: 


行 54:             ti.memo = memo.Text.Trim();
行 55:             table.InsertOnSubmit(ti);
行 56:             dc.SubmitChanges();
行 57:             string CacheName = SiteConfig.PrefixName + dc.Mapping.GetTable(typeof(bx_wap_TypeInfo)).TableName;
行 58:             IXinHuaCache cache = XinHuaCache.Instance();
 

         DataContext dc = DataContextHelper.DataContext;
          Table<bx_wap_TypeInfo> table = dc.GetTable<bx_wap_TypeInfo>();
            bx_wap_TypeInfo ti = new bx_wap_TypeInfo();
           // ti.typeid = 0;typeid是主键未赋值
            ti.typename = tbstypename.Text.Trim();
            ti.typeimg = fileName;
            ti.status = 0;
            ti.cpid = 1;
            ti.parentid =0;
            ti.ctype =1;
            ti.sortid = 0;
            ti.memo = memo.Text.Trim();
            table.InsertOnSubmit(ti);
            dc.SubmitChanges();
            dc.Dispose();

[Table(Name = "bx_wap_TypeInfo")]
    public partial class bx_wap_TypeInfo : ModelBase
    {
        public bx_wap_TypeInfo()
        {
            //base.M_TableName = "bx_wap_TypeInfo";
        }
        #region Model
        private int _typeid;
        private string _typename;
        private string _typeimg;
        private int? _status = 0;
        private int? _cpid = 0;
        private int? _parentid = 0;
        private int? _ctype = 0;
        private int? _sortid = 0;
        private string _memo;
        private DateTime? _addtime = DateTime.Now;
        private int? _totalvideo = 0;
        private int? _delstatus = 0;
      
        /// <summary>
        /// 
        /// </summary>
        [Column(IsPrimaryKey = true)]
        public int typeid
        {

            set { _typeid = value;// base.M_PrimaryKeyID = value; 
            }
            get { return _typeid;   }
        }
        [Column(Name = "typename")]
        public string typename
        {
            set { _typename = value; }
            get { return _typename; }
        }
        [Column(Name = "typeimg")]
        public string typeimg
        {
            set { _typeimg = value; }
            get { return _typeimg; }
        }

        [Column(Name = "status")]
        public int? status
        {
            set { _status = value; }
            get { return _status; }
        }
        [Column(Name = "cpid")]
        public int? cpid
        {
            set { _cpid = value; }
            get { return _cpid; }
        }
        [Column(Name = "parentid")]
        public int? parentid
        {
            set { _parentid = value; }
            get { return _parentid; }
        }
        [Column(Name = "ctype")]
        public int? ctype
        {
            set { _ctype = value; }
            get { return _ctype; }
        }
        [Column(Name = "sortid")]
        public int? sortid
        {
            set { _sortid = value; }
            get { return _sortid; }
        }
        [Column(Name = "memo")]
        public string memo
        {
            set { _memo = value; }
            get { return _memo; }
        }
        [Column(Name = "addtime")]
        public DateTime? addtime
        {
            set { _addtime = value; }
            get { return _addtime; }
        }
        [Column(Name = "totalvideo")]
        public int? totalvideo
        {
            set { _totalvideo = value; }
            get { return _totalvideo; }
        }
        [Column(Name = "delstatus")]
        public int? delstatus
        {
            set { _delstatus = value; }
            get { return _delstatus; }
        }
        #endregion Model

    }