C# - String sorting by other string as helper

Question

Is there a .NET build-in method that would solve my scenario?

Got an array of strings ex. { "Mark", "Tom", "Mat", "Mary", "Peter" }
I use string "Ma" as sorting string helper
My array result is { "Mark", "Mary", "Mat", "Tom", "Peter" }

I know that function solving this would be easy, but I'am interested is such method exists.

PS. Using .NET 4.0

The strings that have the matching index that needs to be sorted. What about the other strings, that do not have the matching string? If you want, you can filter out all the matching string and sort them and finally append the list with remaining elements. — Pawan Mishra
– Pawan Mishra, Commented Nov 16, 2011 at 15:30
What's the benefit of sorting elements that match only the specified prefix while leaving the other elements in their original relative ordering? Do the sorted elements always end up at the beginning? — Jonathon Faust
– Jonathon Faust, Commented Nov 16, 2011 at 15:31

Rich O'Kelly · Accepted Answer · 2011-11-23 12:45:42Z

17

Using .Net 3.5 (and above) the OrderByDescending and ThenBy methods in Linq will be able to do what you want. eg:

var ordered = strings.OrderByDescending(s => s.StartsWith("Ma")).ThenBy(s => s);

edited Nov 23, 2011 at 12:45

answered Nov 16, 2011 at 15:32

Rich O'Kelly

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1 Comment

Derek Dysart Over a year ago

This one's linq-fu is strong. +1

Marco · Accepted Answer · 2011-11-16 15:40:19Z

I think that method does not exist.
I solved with this:

public static string[] Sort(this string[] list, string start)
{
    List<string> l = new List<string>();
    l.AddRange(list.Where(p => p.StartsWith(start)).OrderBy(p => p));
    l.AddRange(list.Where(p => !p.StartsWith(start)).OrderBy(p => p));
    return l.ToArray();
}

So you can do

string[] list = new string[] { "Mark", "Tom", "Mat", "Mary", "Peter" };
string[] ordered_list = list.Sort("Ma");

If you need to order elements with your string and leave others unsorted, use this:

public static string[] Sort(this string[] list, string start)
{
    List<string> l = new List<string>();
    l.AddRange(list.Where(p => p.StartsWith(start)).OrderBy(p => p));
    l.AddRange(list.Where(p => !p.StartsWith(start)));
    // l.AddRange(list.Where(p => !p.StartsWith(start)).OrderByDescending(p => p));
    return l.ToArray();
}

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