Name                        Last modified      Size  Description
 Parent Directory                                 -   
 Dictionary-properties/      2023-05-03 10:20    -   

var myDict = new Dictionary();
.
.
.
var nullKeys = myDict
  .Where(field => string.IsNullOrWhiteSpace(field.Value?.ToString()))
  .Select(field => field.Key)
  .ToList();

foreach(var key in nullKeys)
  myDict.Remove(key);