Remove Characters from a String with limited Memory

How about, If we don't have enough memory we have to use a single array.
Here is how to do that with limited memory

  public static string RemoveCharactersLimited(char[] s, string removeChars)
        {
            int i = 0, j = 0;

            int lengthC = removeChars.Length;
            int lengthS = s.Length;
            int[] intCollection = new int[256];
            
            for (i = 0; i < lengthC; i++)
            {
                intCollection[removeChars[i]] = 1;
            }

            i = j = 0;
            for (i = 0; i < lengthS; i++)
            {
                if (intCollection[s[i]] != 1)
                {
                    s[j] = s[i];
                    j++;
                }
            }
            while (j < lengthS)
            {
                s[j] = '\0';
                j++;
            }

            return new string(s);

        }

Remove Characters from String C#.NET

The string manipulation function removes a set of characters fromthe input string

For example

Removing "RT" from "ROBERT FROST" will give you "OBE FOS"

 public static string RemoveCharacters(string s, string removeChars)
        {
            int i=0,j=0;
            
            int lengthC = removeChars.Length;
            int lengthS = s.Length;
            int[] intCollection = new int[256];
            char[] s2 = new char[lengthS];

            for (i = 0; i < lengthC; i++)
            {
                intCollection[removeChars[i]] = 1;
            }

            i = j = 0;
            for (i = 0; i < lengthS; i++)
            {
                if (intCollection[s[i]] != 1)
                {
                    s2[j] = s[i];
                    j++;
                }
            }

            return new string(s2); 
            
        }