Combine() private static method

private static Combine ( string source, int start, int checkType ) : StringBuilder
source string
start int
checkType int
return StringBuilder
 private static StringBuilder Combine(string source, int start, int checkType)
 {
     for (int i = 0; i < source.Length; i++)
     {
         if (Normalization.QuickCheck(source[i], checkType) != NormalizationCheck.Yes)
         {
             StringBuilder stringBuilder = new StringBuilder(source.Length + source.Length / 10);
             stringBuilder.Append(source);
             Normalization.Combine(stringBuilder, i, checkType);
             return(stringBuilder);
         }
     }
     return(null);
 }
        private static string Compose(string source, int checkType)
        {
            StringBuilder stringBuilder = null;

            Normalization.Decompose(source, ref stringBuilder, checkType);
            if (stringBuilder == null)
            {
                stringBuilder = Normalization.Combine(source, 0, checkType);
            }
            else
            {
                Normalization.Combine(stringBuilder, 0, checkType);
            }
            return((stringBuilder == null) ? source : stringBuilder.ToString());
        }