A simple algorithm of format string(trim the same element of char-set, trans to specified format)

//================Example:=====================//
//give-------"2.12,2.12,3.12-3.5,4.12,4.22-6.33,4.12,12-3.5";   //
//return-----"2.12,3.12-3.5,4.12,4.22-6.33,12-3.5";                   //


private string TrimDateString(string strSource,char charSplit)
  {
   
   string strDes="";
     while(strSource!="")
   {
    string strTemp = strSource.Split(charSplit)[0];
    strSource = strSource.Replace(strTemp,"");
    strSource = strSource.TrimStart(charSplit);
    strSource = strSource.Trim();
    strDes += strTemp+charSplit;
   }
   strDes = strDes.TrimEnd(charSplit);
   return strDes;
   
  }


private string FormatDateString(string strDate)
  {
   //In: 4.1-4.2
   //Out: 2004/04/01~2004/04/02

   string[] strArr = strDate.Split(',');
   string strReturn ="";
   string strYear = DateTime.Now.Year.ToString();
   for (int i=0; i<strArr.Length; i++)
   {
    string[] strTemp = strArr[i].Split('-');
    for(int j=0; j<strTemp.Length; j++)
    {
     string[] strTempMore = strTemp[j].Split('.');
     if (strTempMore.Length == 2)
      strReturn += string.Format("{0}/{1}/{2}~",strYear,(strTempMore[0].Trim().Length<2)?"0"+strTempMore[0].Trim():strTempMore[0].Trim(),(strTempMore[1].Trim().Length<2)?"0"+strTempMore[1].Trim():strTempMore[1].Trim());
    }
    strReturn = strReturn.TrimEnd('~')+",";
    
   }
   
   strReturn = strReturn.TrimEnd(',');
   if (strArr.Length == 1 && strArr[0].Trim()!="" && strArr[0].IndexOf('-')<0)
   {
    strReturn = strReturn +"~"+strReturn;
   }
   return strReturn;
  }