c# - RavenDB count index including zero values -

i have list of items {id, name, categoryid} , list of categories {id, name, isactive}.

how list {categoryid, count} including categories have 0 items.

currently have such index:

public class categorycountindex : abstractindexcreationtask<item, categorycountindex.result> {     public class result     {         public string categoryid { get; set; }         public int count { get; set; }     }      public categorycountindex()     {         map = items => item in items              select new result             {                 categoryid = item.categoryid,                 count = 1             };          reduce = results => result in results             group result result.categoryid             c             select new result             {                 categoryid = c.key,                 count = c.sum(x => x.count)             };     } } 

what best way improve/change solution in order have categories no items?

i removed earlier answer proved incorrect. in case can use multimap/reduce index solve problem.

try using following index:

public class category_items : abstractmultimapindexcreationtask<category_items.reduceresult> {     public class reduceresult     {         public string categoryid { get; set; }         public int count { get; set; }     }      public category_items()     {         addmap<item>(items =>             item in items             select new              {                 categoryid = item.categoryid,                 count = 1             });          addmap<category>(categories =>             category in categories             select new              {                 categoryid = category.id,                 count = 0             });           reduce = results =>             result in results             group result result.categoryid g             select new reduceresult             {                 categoryid = g.key,                 count = g.sum(x => x.count)             };     } } 

this result in following (three categories, 1 without items):

now can use result transformer if want display category name.

hope helps!