C# 列表 - 删除重复项

Question

I have a list that look like this:

U-70754, U-70755
U-70754, U-70755
U-70754, U-70755, U-70786, U-70787, U-70788
U-70754, U-70755, U-70786, U-70787, U-70788
U-70754, U-70755, U-70786, U-70787, U-70788
U-70754, U-70755, U-70786, U-70787, U-70788

I looking for a way to remove duplicates, and rearrange the list so the list will look like this:

U-70754
U-70755
U-70786
U-70787
U-70788

I can't seem to wrap my head around this issue, I hope someone can help.

Thanks in advance!

Answer 1

You can split every item by comma, map the result into one sequence using SelectMany , then use Distinct method to get a unique values

var list = new List<string>
{
    "U-70754, U-70755",
    "U-70754, U-70755",
    "U-70754, U-70755, U-70786, U-70787, U-70788",
    "U-70754, U-70755, U-70786, U-70787, U-70788",
    "U-70754, U-70755, U-70786, U-70787, U-70788",
    "U-70754, U-70755, U-70786, U-70787, U-70788"
};

var result = list.SelectMany(i => i.Split(new [] { ',' })).Distinct().ToList();

Answer 2

If I'm understanding the structure of your list correctly, it looks like each item can contain several comma-separated strings. If that's the case, you can get what you're looking for with a few extra lines:

var filteredList = list.SelectMany(x => x.Split(","))
                       .Select(x => x.Trim())
                       .Distinct()
                       .OrderBy(x => x);

Here's a .NET Fiddle showing it in action.

EDIT : I see Pavel beat me to the punch with essentially the same answer, but this code Trim s the Split strings (without which they won't sort correctly) and then explicitly orders them since Distinct will most likely only preserve the original order.