Vb.net Sorting list [duplicate]

Question

and DN125I have a list with the following values:

   DN32
   DN100
   DN50
   DN80
   DN125
   DN65

I want to sort this list the following way:

DN125       
DN100
DN80     
DN65   
DN50   
DN32

I tried using:

list.sort()
list.reverse()

but this resulted in DN100 and DN125 ending up at the end of the list. so how can I sort this the way I want to?

You'll need a custom comparison that understands the ordering you require. See the Array.Sort documentation.(the right overload will depend on the details of your array which you don't show). — Richard
– Richard, Commented Nov 15, 2017 at 9:46

Tim Schmelter · Accepted Answer · 2017-11-15 09:48:03Z

2

Since the list contains strings, List.Sort will perform an alphanumeric sorting. You want to sort the first part alphabetically and the numerical part numerically, like windows explorer.

If this format is fix(first 2 letters are letters, rest is an integer) you could use this LINQ approach:

list = list.
    Select(Function(s) New With {.String = s, .Letters = s.Remove(2), .Number = Int32.Parse(s.Substring(2))}).
    OrderBy(Function(x) x.Letters).
    ThenBy(Function(x) x.Number).
    Select(Function(x) x.String).
    ToList()

answered Nov 15, 2017 at 9:48

Tim Schmelter

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4 Comments

Fyer-Zero Over a year ago

Works like a charm! Thanks! Added a list.Reverse() to swap the order and now it is perfect.

Tim Schmelter Over a year ago

@Fyer-Zero dont use reverse but OrderByDescending

Fyer-Zero Over a year ago

That also works, saves me a line of code :)

Tim Schmelter Over a year ago

@Flyer: it doesnt only save you a line. You can also use ThenByDescending if you want to sort the ltter part different to the number part. It's also more efficient because a list.Sort at the end would again sort the whole list, so the same procedure again.

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