private void addPersonsButton_Click(object sender, RoutedEventArgs e)
        {
            AddPersonsToMaterialWindow addPersonsToMaterialWindow1 = new AddPersonsToMaterialWindow();
            addPersonsToMaterialWindow1.ShowDialog();

            if (addPersonsToMaterialWindow1.MyDialogResult == true)
            {
                Person p;
                int t;
                
                for (int i = 0; i < addPersonsToMaterialWindow1.SelectedPersonIdList.Count; i++)
                {
                    t = addPersonsToMaterialWindow1.SelectedPersonIdList[i];
                    p = model1.Persons.First(o => o.Id == t);
                    PersonsToAdd.Add(p);
                }
            }
        }
        private void addPersonsButton_Click(object sender, RoutedEventArgs e)
        {
            AddPersonsToMaterialWindow addPersonsToMaterialWindow1 = new AddPersonsToMaterialWindow();

            addPersonsToMaterialWindow1.ShowDialog();

            if (addPersonsToMaterialWindow1.MyDialogResult == true)
            {
                Person p;
                int    t;

                for (int i = 0; i < addPersonsToMaterialWindow1.SelectedPersonIdList.Count; i++)
                {
                    t = addPersonsToMaterialWindow1.SelectedPersonIdList[i];
                    p = model1.Persons.First(o => o.Id == t);
                    PersonsToAdd.Add(p);
                }
            }
        }