Removing duplicates from Array with C#.NET 4.0 LINQ?

Question

I have this c# code that builds a string of comma seperated matches for a service:

for (m = r.Match(site); m.Success; m = m.NextMatch())
{
     found = found + "," + m.Value.Replace(",", "");
}
return found;

Output looks like: aaa,bbb,ccc,aaa,111,111,ccc

Now that code is on .NET 4.0 How can I use C# LINQ to remove duplicates?

Also, Any way to remove duplicates without changing order?

I found this sample code in another post, but not sure exactly how to apply it:

int[] s = { 1, 2, 3, 3, 4}; 
int[] q = s.Distinct().ToArray();

Thanks.

Well, first put the strings you find into an array, see if that helps. You're building up a long string, that won't make it easy to find or remove the duplicates. — Lasse V. Karlsen
– Lasse V. Karlsen, Commented Feb 24, 2011 at 11:44

Stecya · Accepted Answer · 2011-02-24 11:42:30Z

7

string[] s = found.Split(',').Distinct().ToArray()

answered Feb 24, 2011 at 11:42

Stecya

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1 Comment

Hell.Bent Over a year ago

Thanks. And in 4.0, to return s as a single comma sperated string now?

Lasse V. Karlsen · Accepted Answer · 2011-02-24 11:51:45Z

Rewrite the code that builds the result to output it directly.

ie. rewrite this:

for (m = r.Match(site); m.Success; m = m.NextMatch())
{
     found = found + "," + m.Value.Replace(",", "");
}
return found;

To this:

return (from Match m in r.Matches(site)
        select m.Value.Replace(",", "")).Distinct().ToArray();

This will return an array. If you still want it back as a string:

return string.Join(", ", (from Match m in r.Matches(site)
        select m.Value.Replace(",", "")).Distinct().ToArray());

You may or may not be able to remove the last .ToArray() from the last code there depending on the .NET runtime version. .NET 4.0 string.Join(...) can take an IEnumerable<string>, whereas previous versions requires an array.

Oleks · Accepted Answer · 2011-02-24 11:53:50Z

4

This will return a string of comma seperated values without duplicates:

var result = string.Join(",",
    r.Matches(site)
        .Cast<Match>()
        .Select(m => m.Value.Replace(",", string.Empty))
        .Distinct()
    );

answered Feb 24, 2011 at 11:53

Oleks

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1 Comment

Lasse V. Karlsen Over a year ago

For .NET before 4.0, you need to add .ToArray() after distinct.

Volkmar Rigo · Accepted Answer · 2011-02-24 11:56:19Z

4

this could be one possible solution:

var data = new List<string>();
for (m = r.Match(site); m.Success; m = m.NextMatch())
  data.Add(m.Value.Replace(",", ""));
return String.Join(",", data.Distinct().ToArray());

answered Feb 24, 2011 at 11:56

Volkmar Rigo

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Comments

Swinkaran · Accepted Answer · 2013-07-12 02:17:40Z

0

You can achieve this in a single LINQ query

string strSentence = "aaa,bbb,ccc,aaa,111,111,ccc";
List<string> results = (from w in strSentence.Split(',') select w).Distinct().ToList();

answered Jul 12, 2013 at 2:17

Swinkaran

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