Using Split in RavenDB index - ravendb

Question

I'd like to use a couple of regexes in an index. This is a simplified example:
Map =
books =>
books.Select(x => new {Sentences = Regex.Split(x.Description, "<br>")})
.Select(x => new {Results = x.Sentences.Where(y => Regex.IsMatch(y, "foo"))})
.Where(x => x.Results.Any())
.Select(x => new {});
However, the following exception is thrown:
An exception of type 'Microsoft.CSharp.RuntimeBinder.RuntimeBinderException' occurred in System.Core.dll but was not handled in user code
Additional information: 'System.Array' does not contain a definition for 'Where'
I've tried .AsEnumerable() but to no avail. Can this be done?

Answer 1

To fix this, you need to call .AsEnumerable() on the thing you're .Select'ing off.
So instead of Regex.Split(...).Select(...), use Regex.Split(...).AsEnumerable().Select(...)
RavenDB relies on an internal class that knows how to map common extension methods.
Sometimes, however, it may not be able to dynamically resolve the extension methods. To help dynamic resolution, call the .AsEnumerable(), then the extension methods will be found.
Your code should look something like this:
Map =
books =>
books.Select(x => new {Sentences = Regex.Split(x.Description, "<br>")})
.AsEnumerable()
.Select(x => new {Results = x.Sentences.Where(y => Regex.IsMatch(y, "foo"))})
.Where(x => x.Results.Any())
.Select(x => new {});