делаю шаги как в тесте...

    [Record]
    [Table(Name="dbo.CfgIzmeritel")]
    public partial class CfgIzmeritel
    {
        public this() { }
        
        mutable ID_Izmerit : int;
        mutable ID_TypeIzmerit : int;
        
        [Column(Storage="ID_Izmerit", AutoSync=AutoSync.OnInsert, DbType="Int NOT NULL IDENTITY", IsPrimaryKey=true, IsDbGenerated=true)]
        public _ID_Izmerit : int { get { ID_Izmerit; } }
        
        [Column(Storage="ID_TypeIzmerit", DbType="Int")]
        public _ID_TypeIzmerit : int { get { ID_TypeIzmerit; } }
    }

    class LinqDataConnection : DataContext
    {
        public this(connStr : string)
        {
            base(connStr)
        }
        public CfgARM : Table[CfgARM]    { get { GetTable(); } }
        public CfgTypeIzmer : Table[CfgTypeIzmer]    { get { GetTable(); } }
        public CfgIzmeritel : Table[CfgIzmeritel]    { get { GetTable(); } }
    }

    class SQLModule
    {
        public this()
        {
            _conn.Connection.Open();
            _conn2.Connection.Open();
             _CfgTypeIzmer = _conn.CfgTypeIzmer;
             _CfgIzmeritel = _conn.CfgIzmeritel;    
        }
    
        public static Permission : DataTable;
        
        static connSetting : System.Configuration.ConnectionStringSettings = ConfigurationManager.ConnectionStrings["FlowServerConnectionString"];
        static connSetting2 : System.Configuration.ConnectionStringSettings = ConfigurationManager.ConnectionStrings["FlowWebSQL"];
        static conn : SqlConnection = SqlConnection(connSetting.ConnectionString);
        static _conn : LinqDataConnection = LinqDataConnection(connSetting.ConnectionString);
        static _conn2 : WebLinqDataConnection = WebLinqDataConnection(connSetting2.ConnectionString);
        
        public static mutable _CfgTypeIzmer : Table[CfgTypeIzmer];
        public static mutable _CfgIzmeritel : Table[CfgIzmeritel];

...

        public static GetDataString(categoryId : string) : string
        {
            def res = linq<#from i in _CfgIzmeritel
                    where i._ID_Izmerit==int.Parse(categoryId)
                    select (i._ID_TypeIzmerit)
                    #>;
            def ary = res.ToArray();
            ary[0].ToString()

Ругается :

Значение не может быть неопределенным.
Имя параметра: source

Трассировка стека:

[ArgumentNullException: Значение не может быть неопределенным.
Имя параметра: source]
System.Linq.Queryable.Where(IQueryable`1 source, Expression`1 predicate) +581556
Flow_WEB_Nemerle.SQLModule.GetDataString(String categoryId) in ...\Projects\Flow WEB Nemerle\Flow WEB Nemerle\CodeLair\SQLModule.n:148
Flow_WEB_Nemerle.Items.Page_Load(Object _N_wildcard_3268, EventArgs _N_wildcard_3269) in ...\Projects\Flow WEB Nemerle\Flow WEB Nemerle\Items.aspx.n:83
System.Web.Util.CalliHelper.EventArgFunctionCaller(IntPtr fp, Object o, Object t, EventArgs e) +14
System.Web.Util.CalliEventHandlerDelegateProxy.Callback(Object sender, EventArgs e) +35
System.Web.UI.Control.OnLoad(EventArgs e) +99
System.Web.UI.Control.LoadRecursive() +50
System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint) +627

А хотелось бы разобраться с Linq ...
Единственное в

    [Record]
    [Table(Name="dbo.CfgIzmeritel")]

указаны не все столбцы , обязательно указывать все ?