public TagsChangedEventArgs(ViewModels.Tag Tag, string done)
 {
     if (Tag != null && done != null)
     {
         _changedTag = Tag;
         _done       = done;
     }
 }
        private void B_NewTag_Click(object sender, RoutedEventArgs e)
        {
            if (TB_Tags.Text.Contains("'" + TB_NewTag.Text + "',"))
            {
                MessageBox.Show("The Tag '" + TB_NewTag.Text + "' is already assigned to the file.");
                return;
            }

            ViewModels.Tag addTag = new ViewModels.Tag(TB_NewTag.Text);
            sourceFile.Tags.Add(addTag);
            if (!allTags.Contains(addTag))
            {
                allTags.Add(addTag);
            }
            TagsChanged(this, new EventArgs());
        }