public static class JasonHelper

{

    public static string Escape(string s)

    {

        if (s == null)

            return null;

        StringBuilder sb = new StringBuilder();

        for (int i = 0; i < s.Length; i++)

        {

            char ch = s[i];

            switch (ch)

            {

                case '"':

                    sb.Append("\\\"");

                    break;

                case '\\':

                    sb.Append("\\\\");

                    break;

                case '\b':

                    sb.Append("\\b");

                    break;

                case '\f':

                    sb.Append("\\f");

                    break;

                case '\n':

                    sb.Append("\\n");

                    break;

                case '\r':

                    sb.Append("\\r");

                    break;

                case '\t':

                    sb.Append("\\t");

                    break;

                case '/':

                    sb.Append("\\/");

                    break;

                default:

                    sb.Append(ch);

                    break;

            }

        }//for 

        return sb.ToString();

    } 

}