C# 字符串按设置的格试在前面或后面增加空格或其它字符

  public string lengadd(string stringa, string stringb, int count, int mode)  //以stringa的长度,未到count的长度则增加stringb,mode属性0是增加前面,1是增加后面
         {
             int stringaa = System.Text.Encoding.Default.GetBytes(stringa).Length;
             if (mode == )
             {
                 for (int i = ; i <= (count - stringaa); i++)
                 {
                     stringa = stringb + stringa;
                 }

             }
             else
             {
                 for (int i = ; i <= (count - stringaa); i++)
                 {
                     stringa = stringa + stringb;
                 }

             }
             return stringa;
         }