c# - How do we find duplicates in a list of objects -

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• c# linq find duplicates in list 5 answers

how find duplicates in list of objects based on multiple properties?

the following code not returning if list contains dupes or not.

var dups = listitems.groupby(i => new { i.value, i.code })                     .where(g => g.count() >= 1)                     .select(g => new                       {                          length = g.key.value,                         label = g.key.code,                         count = g.count()                       }); 

i guess have error in condition where(g => g.count() >= 1) return groups 1 or more items (actually group have @ least 1 item condition true).

if want duplicates should be: where(g => g.count() > 1).

so result code be:

var dups = listitems.groupby(i => new { i.value, i.code })                     .where(g => g.count() > 1)                     .select(g => new                       {                          length = g.key.value,                         label = g.key.code,                         count = g.count()                      }); 

in way in dups have groups of more 1 items duplicated value , code.

also think better if call select before where because calculating count of items in group twice, inside where check condition , inside select store count.

if call where after 'select' able filter using stored value of group count, this:

var dups = listitems.groupby(i => new { i.value, i.code })                     .select(g => new                       {                          length = g.key.value,                         label = g.key.code,                         count = g.count()                      })                     .where(g => g.count > 1);