Created Method to check wether file is already downloaded.

Using this method when running TaskExecutor.UpdateChapters to get a list of all chapters that have not yet been downloaded.

Tranga/Connector.cs

@@ -77,6 +77,16 @@ public abstract class Connector
         );
         return comicInfo.ToString();
     }
+
+    public bool ChapterIsDownloaded(Publication publication, Chapter chapter)
+    {
+        return File.Exists(CreateFullFilepath(publication, chapter));
+    }
+
+    protected string CreateFullFilepath(Publication publication, Chapter chapter)
+    {
+        return Path.Join(downloadLocation, publication.folderName, chapter.fileName);
+    }
     
     /// <summary>
     /// Downloads Image from URL and saves it to the given path(incl. fileName)

Tranga/Connectors/MangaDex.cs

@@ -201,7 +201,7 @@ public class MangaDex : Connector
         File.WriteAllText(comicInfoPath, CreateComicInfo(publication, chapter));
         
         //Download Chapter-Images
-        DownloadChapterImages(imageUrls.ToArray(), Path.Join(downloadLocation, publication.folderName, chapter.fileName), this.downloadClient, comicInfoPath);
+        DownloadChapterImages(imageUrls.ToArray(), CreateFullFilepath(publication, chapter), downloadClient, comicInfoPath);
     }
 
     public override void DownloadCover(Publication publication)

Tranga/TaskExecutor.cs

@@ -96,11 +96,9 @@ public static class TaskExecutor
         if (!chapterCollection.ContainsKey(publication))
             return newChaptersList;
         
-        List<Chapter> currentChapters = chapterCollection[publication];
         Chapter[] newChapters = connector.GetChapters(publication, language);
+        newChaptersList = newChapters.Where(nChapter => !connector.ChapterIsDownloaded(publication, nChapter)).ToList();
         
-        newChaptersList = newChapters.ToList()
-            .ExceptBy(currentChapters.Select(cChapter => cChapter.url), nChapter => nChapter.url).ToList();
         return newChaptersList;
     }
 }