Addition of MultiSortExtensions to allow easy sorting across multiple fields

[mgoodfellow]

It can be difficult to build multi-level sorting programmatically through the existing interfaces, so these extensions allow a quick way of adding a list of various SortFieldDescriptors

Usage:

// The actual search
var searchResponse =
    this.client.Search<DTO>(
        f => f.Filter(FITLER)
              .Size(SIZE)
              .Query(QUERY)
              .SortMulti(SortMethod(params)));

// This could dynamically build the required sorts based on the parameters passed in (e.g. from UI)
private static IEnumerable<SortFieldDescriptor<DTO>> SortMethod(SortParams params)
{
    IList<SortFieldDescriptor<DTO>> sorts = new List<SortFieldDescriptor<DTO>>();

    if (params.SomeSort.HasValue)
    {
        sorts.Add(new SortFieldDescriptor<DTO>().OnField(f => f.Field).Descending().MissingLast());
    }

    if (params.AnotherSort.HasValue)
    {
        sorts.Add(new SortFieldDescriptor<DTO>().OnField(f => f.Field2).Descending().MissingLast());
    }

    return sorts;
}

[gmarz]

Hey @mgoodfellow thanks for this! I'm liking it a lot, but I have just a few suggestions...

I don't think these need to be extension methods? I can't think of a reason for not just including them as instance methods on SearchDescriptor.

I think I like SortMulti as opposed to MultiSort...better Intellisense discovery, etc. Or maybe just overloading Sort would be better? Not sold on that, just an idea...thoughts?

Lastly, would you mind adding some unit tests for this?

Thanks again, this is great!

[mgoodfellow]

Hi @gmarz,

Thanks for the feedback! Originally I made them as extension methods as this was the easiest way to enhance the functionality while still using the standard Nuget packages.

I agree with the idea to make it SortMulti to enhance the intellisense, but I think overloading Sort might get confusing, so it's good to keep some degree of separation between their functionality.

I have added a couple of tests to check the DSL produced.

Any more comments are more than welcome!

[gmarz]

Awesome, thank you @mgoodfellow. LGTM 👍