private void tabControl1_SelectedIndexChanged(object sender, EventArgs e) { if (tabControl1.SelectedTab.Name == "tabPagePreview" && dataGridView1.CurrentRow != null ) { FileObject a = (FileObject)dataGridView1.CurrentRow.DataBoundItem; richTextBox1.Text = a.GetFileAsString(cde.BasePath); HighlightRTF(richTextBox1); groupBoxSearchInPreview.Enabled = true; } else { groupBoxSearchInPreview.Enabled = false; } }