hardcoded search error messages changed to string resources

VDownload.Sources/VDownload.Sources/SearchService.cs

@@ -58,7 +58,8 @@ namespace VDownload.Sources
                     return await mapping.Service.SearchVideo(url);
                 }
             }
-            throw new MediaSearchException("Source is not supported"); // TODO : Change to string resource
+
+            throw CreateExceptionSourceNotSupported();
         }
 
         public async Task<Playlist> SearchPlaylist(string url, int maxVideoCount)
@@ -72,7 +73,8 @@ namespace VDownload.Sources
                     return await mapping.Service.SearchPlaylist(url, maxVideoCount);
                 }
             }
-            throw new MediaSearchException("Source is not supported"); // TODO : Change to string resource
+
+            throw CreateExceptionSourceNotSupported();
         }
 
         #endregion
@@ -81,14 +83,17 @@ namespace VDownload.Sources
 
         #region PRIVATE METHODS
 
-        private void BaseUrlCheck(string url)
+        protected void BaseUrlCheck(string url)
         {
             if (string.IsNullOrWhiteSpace(url))
             {
-                throw new MediaSearchException("Url cannot be empty"); // TODO : Change to string resource
+                throw CreateExceptionEmptyUrl();
             }
         }
 
+        protected MediaSearchException CreateExceptionSourceNotSupported() => new MediaSearchException("SourceNotSupported");
+        protected MediaSearchException CreateExceptionEmptyUrl() => new MediaSearchException("EmptyUrl");
+
         #endregion 
     }
 }