Test is a list of object, I ordered and grouped them by the "Total" property as this:

Dim duplicates = test.GroupBy(Function(i) i.Total) _
                            .Where(Function(x) x.Count() > 1) _
                            .[Select](Function(x) x).ToList

After doing dome test I found that with large list it get too much memory, so I'd like to do it in place(I searched on S.O. and web, and as I understood, Linq is not the way for in place way.) Any advice?

CodePudding user response：

Solved implementing Icompare interface