ContentSearchAPI items array relevancy ranking

Question

I'm trying to implement a tagging functionality that allows the content editor to add tags for a specific component and the c# to search for items containing a given set of tags

Let's say our Sitecore Lucene index looks like this

x = ["csharp", "dotNet", "java", "vbnet", "c"]
y = ["csharp", "computers", "dotNet"]
z = ["java"]

I want to perform a search query like this

["csharp", "dotNet"]

and have it return x and y, but y will be scored/ranked higher than x because it has more matches than any other items in the index...

I'm familiar with Elastic Search(which is built on Lucene) and I know the way to do this is

{
  "terms" : {
      "tags" : [ "csharp", "dotNet" ]
  }
}

but unsure as the same can be achieved using the ContentSearchAPI in Sitecore Lucene.

My current code is

        var tags = GetTagsFromSomewhere();

        using (var context = SearchIndexResolver.GetIndex(ContextItem).CreateSearchContext())
        {
            var queryable = context.GetQueryable<CustomType>();

            foreach (var tag in tags)
            {
                queryable = queryable
                    .Where(i => i.Tags.Contains(tag));

                var results = queryable.GetResults();
            }
        }

Thanks

Answer 1

It's possible to implement. Try something like below:

var tags = GetTagsFromSomewhere();

            using (var context = SearchIndexResolver.GetIndex(ContextItem).CreateSearchContext())
            {
                var queryable = context.GetQueryable<CustomType>();

                var predicat = PredicateBuilder.False<BaseIndexModel>();

                foreach (var tag in tags)
                {
                    predicat = predicat.Or(q => q.Tags.Contains(tag).Boost(1.5f));
                }

                queryable = queryable.Where(predicat);

                var results = queryable.GetResults();
            }

It works for me locally (similar code).

I've a bit updated your code with added a boosting for a condition. In general the boosting allows us to increase a wight of coditions (or Items, Fields. Read more about Search result boosting).

Also I've used a PredicateBuilder, which allows us to build queries more flexible. You can read, for example, the following article about using PredicateBuilder: Building Dynamic Content Search LINQ Queries In Sitecore by Dan Cruickshank