title: can't remove the reserved character?
body: <p>I am trying to remove the reserved character but after calling my function it returns the same input..</p>
  
  <pre><code>        public static void Main(string[] args)
          {
              string text = "erhan?test*.pdf";             
  
              remove(text);
  
              Console.WriteLine("This is your result : {0}", text);
              Console.ReadLine();           
  
          }
  
           private static string remove(string str){
  
               StringBuilder sb = new StringBuilder();
               foreach (char c in str)
               {
                   if (Char.IsLetterOrDigit(c) || c == '.' || c == '_' || c == ' ' || c == '%')
                   { sb.Append(c); }
               }
               return sb.ToString();
          }
  </code></pre>