Remove Duplicates and Original from C# List

Question

I have a List of custom types where I want to remove the duplicate and the original if a duplicate is found. Can only be one possible duplicate.

I can overide Equals and GetHashCode and then use Distinct but this only removes the duplicate. I need to remove both original and duplicate... Any ideas for something elegant so I don't have to use a hammer.

can you provide a coded example of what it is you are working with this will actually help others to gain an understanding of what you are trying to do — MethodMan
– MethodMan, Commented May 16, 2013 at 20:41

Sergey Kalinichenko · Accepted Answer · 2013-05-16 20:41:10Z

6

You can use GroupBy, followed by Where (g => g.Count() == 1) to filter out all records that have duplicates:

var res = orig.GroupBy(x => x).Where(g => g.Count() == 1).Select(g => g.Key);

In order for this to work, you still need to override GetHashCode and Equals.

answered May 16, 2013 at 20:41

Sergey Kalinichenko

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Servy · Accepted Answer · 2013-05-16 20:41:18Z

3

var itemsExistingExactlyOnce = list.GroupBy(x => x)
    .Where(group => group.Count() == 1)
    .Select(group => group.Key);

answered May 16, 2013 at 20:41

Servy

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