Work with a Word Template in C #,

There is a button on the form with this code

private void q1z_Click(object sender, EventArgs e) { WordDocument wordDoc = null; try { wordDoc = new WordDocument(pathToTemplate); if (q1.Checked) { wordDoc.ReplaceAllStrings(q1marks.Text, q1.Text); } else { wordDoc.SetSelectionToText(q1marks.Text); wordDoc.Selection.Text = q1.Text; } } catch (Exception error) { if (wordDoc != null) { wordDoc.Close(); } MessageBox.Show("Ошибка при замене текста на метке в документе Word. Подробности " + error.Message); return; } wordDoc.Visible = true; 

and 2 textboxes, in one I write a label, for example @@ a, in the second a text that will replace this label in the Word. With the help of the checkbox, you can also replace all labels with your own text at the same time. The problem is that when compiling, the studio stresses me here if (q1.Checked) , Cheked and says (see screenshot)

Tell me what kind of error it is and how to remove it, in another project, the code is the same - and everything works?