Splitting Farsi Characters including StandAlone characters

Checking MSDN it looks as though you'll need to use System.Globalization.StringInfo.ParseCombiningCharacters and StringInfo.TextElementEnumerator
There's some example code here:
TextElementIterator
ParseCombiningCharacters

Noddy example:

StringBuilder b = new StringBuilder();
StringInfo si = new StringInfo("αβγδεζηθικλμνξοπρστυφχψωέϊή");
Console.WriteLine(si.LengthInTextElements);

TextElementEnumerator iter = StringInfo.GetTextElementEnumerator("αβγδεζηθικλμνξοπρστυφχψωέϊή");
while (iter.MoveNext()) {
  b.Append(iter.GetTextElement()).Append(" ");
  }

 MessageBox.Show(b.ToString());