c# - LINQ Left Outer join with group by count through extension methods -


i have 2 tables. categories , ads.

every category can have many ads in ads table.

i want categories details including how many ads have each.

following linq expression fetches categories have ads may bacause firstordefault()

i know how can achieve result given condition plus categories have location id (let say: lid) of "7".

following in expression

var x1 = context.categories                 .groupjoin(                     context.ads,                     cat => cat.id,                     ad => ad.catid,                     (cat, ad) => new { cats = cat, ads = ad })                 .selectmany(                     => a.ads.defaultifempty(),                     (a, y) => new { catss = a.cats, adss = y })                 .groupby(w => w.adss,ww=>new {  cat=ww.catss,count=ww.catss.ads.count()})                 .where(s=>s.firstordefault().cat.lid==7);

you try following:

var result = context.categories                     .where(category => category.lid == 7)                     .groupjoin(                         context.ads                         , category => category.id                         , ad => ad.catid                         , (c,a) => new                          {                              category = category,                              numberofads = a.defaultifempty().count(x => x!=null)                         });

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