How to know the file contains some of charecters

This should do it. varaible outputFiles contain the list of files containing the character you are expecting.

string[] files = Directory.GetFiles("D:\\Visual Studio Stuff"); // get the files you want
List<char> charList = new List<char>(); // your list of characters
charList.Add('x');
charList.Add('z');
var outputFiles = files.Where(x => x.ToCharArray().Intersect(charList).Count()>=1).Select(y=>y); // for each of the files, convert to char array and intersect with charaterlist and
// get the files names where intersect returned some value(s).