F # Linq To SQL committing changes does nothing

Question

I have the following class defined in F #, with display attributes for Linq to SQL:

[<Table(Name="Expense")>]
type public Expense(datetime : Nullable<DateTime>, value, category, comment) = 
    let mutable id = 0
    let mutable datetime = if datetime.HasValue then datetime.Value else DateTime.Now
    let mutable value = value
    let mutable category = category
    let mutable comment = comment
    [<Column(IsPrimaryKey=true, IsDbGenerated=true, AutoSync=AutoSync.OnInsert)>]
    member x.ExpenseID with get() = id and set v = id <- v
    [<Column>]
    member x.DateTime with get() = datetime and set v = datetime <- v
    [<Column>] 
    member x.Value with get() = value and set v = value <- v
    [<Column>] 
    member x.Category with get() = category and set v = category <- v    
    [<Column>] 
    member x.Comment with get() = comment and set v = comment <- v
    new() = Expense(nl, 0m, "", "")

Then I want to insert a new object of this type using the following code (snippet):

member private x.expenses = (new DataContext(connString)).GetTable<Expense>()
    member x.Add (expense : Expense) = 
        x.expenses.InsertOnSubmit(expense)
        x.expenses.Context.SubmitChanges()

A call to the SubmitChanges () method does nothing, and no exception is thrown. So I tried to check if there is something that is an F # object, and I declared another class in C # with exactly the same mappings. Then I was able to insert a new record. Now I wonder what's the difference?

Was there some kind of reflector research, the only difference was the [CompilerGenerated] attributes on C # autocaptures / setters and [Serializable] and CompilationMapping (SourceConstructFlags.ObjectType)] in the F # class ... could this be one of those?

: http://pastebin.com/qTRfVcmm

//EDIT

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Answer 1

member. F # ( ) , , x.expenses, . , let:

type SomeType() =
  let expenses = (new DataContext(connString)).GetTable<Expense>()     
  member x.Add (expense : Expense) =          
    expenses.InsertOnSubmit(expense)
    expenses.Context.SubmitChanges() 

member x.Foo = <expr> F # getter, # :

Table<Expenses> Expenses {
  get { return (new DataContext(connString)).GetTable<Expense>(); }
}

..., , .