Question

e.g String1 = "Hello";
e.g String2 = "eo";

I want to remove all chars in string1 that are in string2.
So the output should be "Hll"

Answer 1

Not the most efficient but a very readable solution:

string input = "hello";
string dupes = "eo";

var output = new string((from c in input where !dupes.Contains(c) select c).ToArray());

A more efficient approach for large strings would be using a Hashset<char> for the dupes:

string input = "hello";
string dupes = "eo";

HashSet<char> dupeSet = new HashSet<char>();
foreach (char c in dupes)
    dupeSet.Add(c);

var output = new string(input.Where(c => !dupeSet.Contains(c)).ToArray());