c# - remove duplicates from each group after .GroupBy() -

var groupedlist = mylist.groupby(mytype => mytype.category).tolist() 

groupedlist ienumerable<igrouping<category, mytype>>

now distinct() on specific property of mytype each igrouping<category, mytype> remove duplicates. return value needs same type groupedlist.

so here solution. it's not ideal in terms of performance, in groupby @ end bit redundant, proper types it's not super expensive operation, should enough.

groupedlist = groupedlist.selectmany(group =>     group.distinctby(mytype => mytype.someproperty)         .select(item => new         {             key = group.key,             element = item,         })) .groupby(pair => pair.key, pair => pair.element) .tolist(); 

if create group class, so:

public class group<tkey, telement> : igrouping<tkey, telement> {     private ienumerable<telement> elements;      public group(tkey key, ienumerable<telement> elements)     {         this.elements = elements;         key = key;     }      public tkey key { get; private set; }      public ienumerator<telement> getenumerator()     {         return elements.getenumerator();     }      ienumerator ienumerable.getenumerator()     {         return getenumerator();     } }  public static group<tkey, telement> creategroup<tkey, telement>(     tkey key, ienumerable<telement> elements) {     return new group<tkey, telement>(key, elements); } 

then can do:

groupedlist = groupedlist.select(group =>     (igrouping<string, foo>)creategroup(group.key,         group.distinctby(mytype => mytype.someproperty)))     .tolist();