Do not close workbook on merge if opened

RhSolutions.AddIn/Services/ExcelReader.cs

@@ -156,6 +156,10 @@ public class ExcelReader : IReader, IDisposable
 
     public List<(string, Dictionary<Product, double>)> ReadProducts(string[] files)
     {
+        HashSet<string> openedFiles = RhSolutionsAddIn.Excel.Workbooks
+            .Cast<Workbook>()
+            .Select(wb => wb.FullName)
+            .ToHashSet();
         _progressBar = new("Открываю исходные файлы...", files.Length);
         List<Worksheet> worksheets = new();
 
@@ -170,7 +174,11 @@ public class ExcelReader : IReader, IDisposable
         var result = ReadProducts(worksheets);
         foreach (var ws in worksheets)
         {
-            ws.Parent.Close();
+            string file = (string)ws.Parent.FullName;
+            if (!openedFiles.Contains(file))
+            {
+                ws.Parent.Close(SaveChanges: false);
+            }
         }
         return result;
     }