c# - Exception when a path to a file is null (when you cancel OpenFiledDalog) -

this code:

openfiledialog openfiledialog1 = new openfiledialog();          dialogresult result = openfiledialog1.showdialog(); // show dialog.         if (result == dialogresult.ok) // test result.         {             string file = openfiledialog1.filename;          }         else { messagebox.show("error."); }  //later on..         datatable lertableec0 = new datatable();         lertableec0.readxml(openfiledialog1.filename); 

and right here in end comes error, works fine, xml import, etc if cancel in open dialog exception, hint?

(there ir similar question answer still confusing me

  return null;     

didnt work me

  if (result == dialogresult.ok) // test result.   {         string file = openfiledialog1.filename;          datatable lertableec0 = new datatable();         lertableec0.readxml(openfiledialog1.filename);          }  else {         messagebox.show("error.");   } 

since filename not set if cancel button clicked , empty string passed readxml() function throws exception . have move function inside ok click condition