diff --git a/Lib_CSharp b/Lib_CSharp
index 9edfc6be..ce4a59cf 160000
--- a/Lib_CSharp
+++ b/Lib_CSharp
@@ -1 +1 @@
-Subproject commit 9edfc6be872db708abd986d9504800da41b2a9bb
+Subproject commit ce4a59cf4a90cf74a3a9116ccbaf6d2e588dc8ad
diff --git a/PoliNetwork.Graduatorie.Parser/Objects/Json/DateFound.cs b/PoliNetwork.Graduatorie.Parser/Objects/Json/DateFound.cs
index e12a861f..c3d1aea8 100644
--- a/PoliNetwork.Graduatorie.Parser/Objects/Json/DateFound.cs
+++ b/PoliNetwork.Graduatorie.Parser/Objects/Json/DateFound.cs
@@ -23,29 +23,47 @@ public void WriteToFile(string dataFolder)
         File.WriteAllText(path, s);
     }
 
-
-    public static DateTime MinDateTime(DateTime date1, DateTime date2)
+    public static DateTime? MinDateTime(DateTime? date1, DateTime? date2)
     {
+        if (date1 == null && date2 == null)
+            return null;
+        if (date1 == null)
+            return date2;
+        if (date2 == null)
+            return date1;
+
         return date1 < date2 ? date1 : date2;
     }
 
     public void UpdateDateFound(Ranking variable)
     {
         var path = variable.GetPath().Trim();
+        var minDateTime = GetMinTime(variable, path);
+        SetDate(path, minDateTime);
+    }
 
+    private void SetDate(string path, DateTime? minDateTime)
+    {
         FirstDate ??= new SortedDictionary<string, DateTime?>();
+        FirstDate[path] = minDateTime;
+    }
 
+    private DateTime? GetMinTime(Ranking variable, string path)
+    {
+        FirstDate ??= new SortedDictionary<string, DateTime?>();
         var dateTime = new DateTime(variable.Year ?? DateTime.UtcNow.Year, DateTime.UtcNow.Month, DateTime.UtcNow.Day);
-        if (FirstDate.TryGetValue(path, out var oldValue))
-        {
-            if (oldValue == null)
-                FirstDate[path] = dateTime;
-            else
-                FirstDate[path] = MinDateTime(dateTime, oldValue.Value);
-        }
-        else
+        var tryGetValue = TryGetValue(FirstDate, path);
+        var minDateTime = tryGetValue.Item2 switch
         {
-            FirstDate[path] = dateTime;
-        }
+            true => MinDateTime(dateTime, tryGetValue.Item1),
+            _ => dateTime
+        };
+        return minDateTime;
+    }
+
+    public static Tuple<T?, bool> TryGetValue<T>(SortedDictionary<string, T> d, string path)
+    {
+        var tryGetValue = d.TryGetValue(path, out var oldValue);
+        return new Tuple<T?, bool>(oldValue, tryGetValue);
     }
 }
\ No newline at end of file
diff --git a/PoliNetwork.Graduatorie.Parser/Objects/Json/Indexes/Specific/BySchoolYearCourseJson.cs b/PoliNetwork.Graduatorie.Parser/Objects/Json/Indexes/Specific/BySchoolYearCourseJson.cs
index 380a36af..d13ff51d 100644
--- a/PoliNetwork.Graduatorie.Parser/Objects/Json/Indexes/Specific/BySchoolYearCourseJson.cs
+++ b/PoliNetwork.Graduatorie.Parser/Objects/Json/Indexes/Specific/BySchoolYearCourseJson.cs
@@ -262,17 +262,15 @@ SingleCourseJson variable
 
     private static void AddToRankings(ICollection<Ranking> rankings, Ranking ranking)
     {
-        if (
-            rankings.Any(
-                x =>
-                    x.School == ranking.School
-                    && x.Year == ranking.Year
-                    && Similar(x.ByCourse, ranking.ByCourse)
-            )
-        )
-            return;
-
-        rankings.Add(ranking);
+        var any = rankings.Any(
+            x =>
+                x.School == ranking.School
+                && x.Year == ranking.Year
+                && Similar(x.ByCourse, ranking.ByCourse)
+        );
+        
+        if (!any) 
+            rankings.Add(ranking);
     }
 
     private static bool Similar(
@@ -282,7 +280,10 @@ private static bool Similar(
     {
         if (a == null || b == null)
             return false;
-        return a.Count == b.Count
-               && a.Select(variable => b.Any(x => x.Title == variable.Title)).All(boolB => boolB);
+        return a.Count == b.Count && a.Select(Selector).All(Predicate);
+        
+        bool Selector(CourseTable variable) => b.Any(x => x.Title == variable.Title);
+        bool Predicate(bool boolB) => boolB;
+  
     }
 }
\ No newline at end of file