Updated distinct count expression to always use COUNTROWS( ALLNOBLANKROW(..) )

Author: albertospelta

src/Dax.Model.Extractor/StatExtractor.cs

@@ -237,9 +237,10 @@ private static string EscapeTableName(Table table)
 
         private static string DistinctCountExpression(Column column)
         {
-            return column.GroupByColumns.Count == 0 
-                ? $"DISTINCTCOUNT({EscapeColumnName(column)})"
-                : $"COUNTROWS(ALLNOBLANKROW({EscapeColumnName(column)}))";
+            // We always use COUNTROWS(ALLNOBLANKROW(t[c])) instead of DISTINCTCOUNT(t[c]) because it is compatible with GroupByColumns settings, such as Fields Parameters. 
+            // COUNTROWS(ALLNOBLANKROW()) always reads the list of values from the attribute hierarchy (when AvailableInMDX=true) or queries the table if the hierarchy is not available (when AvailableInMDX=false)
+
+            return $"COUNTROWS(ALLNOBLANKROW({EscapeColumnName(column)}))";
         }
 
         private static string EscapeColumnName(Column column)