Following code will remove all non-printable characters from a string.

 StringBuilder cleanString = new StringBuilder();
 foreach (char character in inputString)
 {
     if (Char.IsControl(character))
     {
         if (Char.IsWhiteSpace(character))
         {
             cleanString.Append(" ");
         }
         continue;
     }
     cleanString.Append(character);
 }

If you need to add attributes on properties in a generated class, you can do this by using following pattern.

[MetadataType(typeof(TimeFrame_Extension))]
public partial class TimeFrame { }

public class TimeFrame_Extension
{
    [XmlIgnore]
    public string From { get; set; }

    [XmlIgnore]
    public string To { get; set; }
}

source : http://ardalis.com/adding-attributes-to-generated-classes