Task: Strip control codes and extended characters from a string
C: #include <stdlib.h>
#include <stdio.h>
#include <string.h>

#define MAXBUF 256  
#define STR_SZ 100   



int ascii (const unsigned char c);

int ascii_ext (const unsigned char c);

unsigned char* strip(unsigned char* str, const size_t n, int ext );


 
int ascii (const unsigned char c) 
{  
  unsigned char min = 32;   
  unsigned char max = 126;  

  if ( c>=min && c<=max ) return 1;

  return 0;
} 


 
int ascii_ext (const unsigned char c) 
{  
  unsigned char min_ext = 128;   
  unsigned char max_ext = 255;

  if ( c>=min_ext && c<=max_ext )
       return 1;

  return 0;
} 




unsigned char* strip( unsigned char* str, const size_t n, int ext) 
{ 

  unsigned char buffer[MAXBUF] = {'\0'};

  size_t i = 0;  
  size_t j = 0;  

  size_t max = (n<MAXBUF)? n : MAXBUF -1;  

  while (i < max )
    {
      if ( (ext && ascii_ext(str[i]) ) ||  (ascii(str[i]) ) )    
	{
	  buffer[j++] = str[i]; 
	}      
      i++;
    }

  memset(str, '\0', max); 

  i = 0;               

  while( i < j)
    {
      str[i] = buffer[i]; 
      i++;
    }

  str[j] = '\0';  

  return str;  
}


int main( int argc, char** argv)
{
  enum {ASCII=0, EXT=1}; 

  unsigned int seed = 134529;  

  
  unsigned char badstring[STR_SZ] = {'\0'};
  unsigned char bs_2[STR_SZ]      = {'\0'};
 
  unsigned char* goodstring = NULL;
  unsigned char* goodstring_ext = NULL;

  size_t i = 0;

  srand(seed); 

  fprintf(stdout, "Original:\t" );

  
  for (i = 0; i < STR_SZ; i++)
    {
      badstring[i] = (unsigned char) ( rand () & (unsigned char)0xFF );
      fprintf(stdout, "%c", badstring[i] );
    }
  fprintf(stdout, "\n");

   
   memcpy(bs_2, badstring, STR_SZ * sizeof(unsigned char) ); 

   goodstring_ext = strip( badstring, STR_SZ, EXT); 

   fprintf(stdout, "\nEXT:\t%s\n" , goodstring_ext );

   goodstring = strip( bs_2, STR_SZ, ASCII); 
  
   fprintf(stdout, "\nASCII:\t%s\n" , goodstring );
  
return 0;
}

C#: using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace RosettaCode
{
    class Program
    {
        static void Main(string[] args)
        {
            string test = "string of ☺☻♥♦⌂, may include control characters and other ilk.♫☼§►↔◄";
            Console.WriteLine("Original: {0}", test);
            Console.WriteLine("Stripped of control codes: {0}", StripControlChars(test));
            Console.WriteLine("Stripped of extended: {0}", StripExtended(test));
        }

        static string StripControlChars(string arg)
        {
            char[] arrForm = arg.ToCharArray();
            StringBuilder buffer = new StringBuilder(arg.Length);
            
            foreach(char ch in arrForm)
                if (!Char.IsControl(ch)) buffer.Append(ch);

            return buffer.ToString();
        }

        static string StripExtended(string arg)
        {
            StringBuilder buffer = new StringBuilder(arg.Length); 
            foreach(char ch in arg)
            {
                UInt16 num = Convert.ToUInt16(ch);
                
                if((num >= 32u) && (num <= 126u)) buffer.Append(ch);
            }
            return buffer.ToString();
        }
    }
}