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sqlite-net-pcl (1.4.118) query not supported?

BLWNKLJMOOSEBLWNKLJMOOSE Member ✭✭
in Xamarin.iOS

I'm developing an IOS app using VS for Mac.

This query for multiple data items fails internally

       IEnumerable<MyData> lst = database.Table<MyData>().Where(
            cw => (cw.Timestamp.Date >= fromdate.Date &&
                   cw.Timestamp.Date <= todate)).Select(r =>
            new MyData(r));

If I "break" right after this executes, attempting to examine the "IEnumerator" member
of "lst" gives the following error:

System.NotSupportedException: Member access failed to compile expression

I have already tried disabling the "use MSBuild instead of XBuild" as some posts
recommended. And I added this to my .csproj file:

mcs.exe

All I want to do is get a List out of the query, in any way possible.
Ideally, I'd write:
return lst.AsQueryable().ToList();
(the "AsQueryable()" may not be needed; tbd).
Any help is very much appreciated!
Thanks!!!

Answers

  • ColeXColeX Member, Xamarin Team Xamurai

    You mixed up the usage of Linq syntax.

    Here it does not need Select

         IEnumerable<MyData> lst = database.Table<MyData>().Where(
        cw => (cw.Timestamp.Date >= fromdate.Date &&
               cw.Timestamp.Date <= todate));
  • BLWNKLJMOOSEBLWNKLJMOOSE Member ✭✭

    While your answer seems plausible, the end result is identical; i.e.-
    the IEnumerator member of "lst" still exhibits the error:
    System.NotSupportedException: Member access failed to compile expression.
    (and of course, lst.ToList() croaks, as it relies on IEnumerable).
    I can't help thinking that I've got something configured incorrectly, OR there's
    an actual bug in enumerable query results (but that just seems so unlikely, for
    something this basic!).
    :( Not sure where to poke next.

  • BLWNKLJMOOSEBLWNKLJMOOSE Member ✭✭
    edited August 2018

    After some more digging I found that the Table I am querying has NO records
    satisfying the Where constraints. I can work around this, but I'd still expect the
    query result to be an empty set (i.e. Enumerable to 0 count). Now, this feels like
    a bug! :)
    UPDATE: having no matching records was a red herring. Issue persists. BTW, removing
    the Where clause (getting ALL rows in table) works fine. Obviously, I don't want to do that :)

  • ZoliZoli NLMember ✭✭✭

    Yes, it's a known issue: https://github.com/praeclarum/sqlite-net/issues/535

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