C#:How to evaluate a excel formula consisting of Name ranges using NPOI or any other library -

i have formula in excel cell using name range defined using name manager. how can evaluate formula using npoi or other library in c#?

example: have formula below

=if(isblank(\_namerange1\_),"0",2) 

where _namerange1_ defined "sheet1!$a$9:$ds$9"

i managed after going through few blogs. may there better way below approach resolved issue using npoi library.

string sheetname="sheetname"; // sheetname workbook int row=2;//some desired row int col=5 //some desired col       xssfworkbook hssfwb = new xssfworkbook(new file("filepath");         isheet sheet = hssfwb.getsheet(sheetname);          xssfformulaevaluator evaluator = new xssfformulaevaluator(hssfwb);          //get cell formula defined names         string formula=sheet.getrow(row).getcell(col).cellformula;          //extract defined names formula         var regexcollection=regex.matches(formula,"_\\w+");          foreach (match item in regex_regexcollection)          {           string namerange=hssfwb.getname(item.value).referstoformula     //replace defined names in formula with actual name ranges           formula = formula.replace(item.value, namerange);          }          //set new formula cell again after name replacement         sheet.getrow(row).getcell(col).cellformula = formula;          cellvalue currentcell=evaluator.evaluate(sheet.getrow(row).getcell(col));          string dataformat = sheet.getrow(cellrow).getcell(cellcol).cellstyle.getdataformatstring();            switch (currentcell.celltype)                     {                         case celltype.unknown: return "unknown";                          case celltype.numeric:                              return currentcell.numbervalue.tostring(dataformat);                           case celltype.string:                             return currentcell.stringvalue;                          case celltype.formula: return currentcell.stringvalue;                          case celltype.blank: return "";                          case celltype.boolean: return currentcell.booleanvalue.tostring();                          case celltype.error:                             return "error";                          default:                             return "";                     }