Program to find the ocurence of character in a string

I have a significant improvement using LINQ from solution 3:

str.ToCharArray().GroupBy(i => i).OrderBy(k => k.Key).ToList().
  ForEach(m => Console.WriteLine(string.Format("{0}: {1}", m.Key, m.Count())));

Sniff, sniff... Yep, smells like homework!

Sorry, but the answers you got will probably get you a failing grade in your class. With the level of the assignment you got, there's no way your class covered the methods demonstrated in the answers you got here and the person teaching the class will KNOW you didn't write the code.

string charapp = "NAMAN";
string data = charapp.Distinct().Select(m => new { Key = m, Val = charapp.Count(x=> x.Equals(m)).ToString() }).
Select(m=> m.Key + ":" + m.Val).Aggregate((a,b)=> a + "\n" + b);

Debug.Write(data);

int count = inputstring.Count(f => f == 'N');

If you don't want to use LINQ you can use below

int count = inputstring.Split('N').Length - 1;