如何使用LINQ从字符串中获取重复字符数组？

Question

如果我有以下字符串:

string s = "abcdefghab";

那么我如何获得一个字符串(或char []),它只包含使用C#和LINQ在原始字符串中重复的字符.在我的例子中,我想以"ab"结束.

虽然没有必要,但我试图在一行LINQ中做到这一点,到目前为止已经提出:

s.ToCharArray().OrderBy(a => a)...

Answer 1

String text = "dssdfsfadafdsaf";
var repeatedChars = text.ToCharArray().GroupBy(x => x).Where(y => y.Count() > 1).Select(z=>z.Key);

Answer 2

string theString = "abcdefghab";

//C# query syntax
var qry = (from c in theString.ToCharArray()
           group c by c into g
           where g.Count() > 1
           select g.Key);

//C# pure methods syntax
var qry2 = theString.ToCharArray()
            .GroupBy(c => c)
            .Where(g => g.Count() > 1)
            .Select(g => g.Key);

Answer 3

另外,字符串已经是IEnumerable,所以你真的不需要调用ToCharArray();

var qry = (from c in theString
           group c by c into g           
           where g.Count() > 1           
           select g.Key);

将qry作为IEnumerable,但如果你真的需要一个char [],就像那样简单qrt.ToArray().