Enumerating return list from simple.data

Question

I am attempting to process results from a select (Find.., All, etc) from simple.data, but I am getting errors:

var db = Database.Open();
var codes = db.Code.All();

// 'object' does not contain a definition for 'First'
var firstcode = codes.First();
// 'object' does not contain a definition for 'ToList'
List<Code> codeList = codes.ToList();

The type of codes is {System.Linq.Enumerable.WhereSelectListIterator<System.Collections.Generic.IDictionary<string,object>,Simple.Data.DynamicRecord>}.

What am I missing? Someone add a simple.data tag please.. :)

score 6 · Answer 1 · answered Aug 12 '11 at 00:31

The main reason that LINQ methods don't work on the object returned from db.Code.All() is that at that point in the code, the C# compiler doesn't know that it's an IEnumerable, so it can't hook up the extension methods. Of course, the C# compiler doesn't know what the object is, because it's dynamic, so it passes over it and assumes that the First() method will be resolved at runtime.

I've tried to address this in more recent releases, and many methods are supported, including ToList, First, FirstOrDefault, Single, SingleOrDefault and some others. Still more are to come soon (within the 0.9.x releases).

The easiest way to bring the compiler back into full effect is to explicitly specify the type instead of using var. For example

IEnumerable<Code> codes = db.Codes.All();

will cause an "implicit cast" (quoted because it's not really, but it acts like one) from the SimpleQuery type to the IEnumerable type, at which point you can start using LINQ methods on it again.

Sprintstar · Accepted Answer · 2012-08-29T09:01:54.693

2

Doh, simple answer. I was using the latest version from https://github.com/markrendle/Simple.Data/downloads but in fact it should installed from nuget http://nuget.org/List/Packages/Simple.Data.Core.. :(

edited Aug 29 '12 at 09:01

answered May 25 '11 at 11:56

Sprintstar

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score 1 · Answer 3 · answered May 25 '11 at 11:07

1

It looks like you need a using System.Linq; declaration.

If the actual error message contains the word 'object' then it indicates that the type of codes returned from your call is an object, not a System.Linq.Enumerable.WhereSelectListIterator<System.Collections.Generic.IDictionary<string,object>,Simple.Data.DynamicRecord>} as you say, which would be the cause of the error.

answered May 25 '11 at 11:07

George Duckett

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I have 'using System.Linq' already. I am able to do linqy stuff on other non simple.data collections in that class.. :( – Sprintstar May 25 '11 at 11:15
Take a look at the second part of my answer. – George Duckett May 25 '11 at 11:17
But that type was copied from Visual Studio debugger at a break point, that's what VS thinks it is.. :( – Sprintstar May 25 '11 at 11:28
That's probably the type of `Code`, but not the type of `codes`. As @Manatherin says, the `All()` method returns a boolean result. – George Duckett May 25 '11 at 15:21

Enumerating return list from simple.data

3 Answers3