test.cs

        private void btnSave_Click(object sender, EventArgs e)
        {

            string connStr = @"Data Source=(LocalDB)\v11.0;AttachDbFilename=|DataDirectory|\LitMapPoltavaData.mdf;Integrated Security=True";
            SqlConnection conn = new SqlConnection(connStr);
            try
            {
                //пробуем подключится
                conn.Open();

                // должно быть 3
                int before = (int)(new SqlCommand("SELECT COUNT(*) FROM Writers", conn).ExecuteScalar());

                SqlCommand cmd = new SqlCommand("Insert Into Writers (Id, Surname, Name, Lived, Birthplace, ShortInfo)" +
                    "Values(@Id, @Surname, @Name, @Lived, @Birthplace, @ShortInfo)", conn);

                // Добавить параметры
                cmd.Parameters.AddWithValue("@Id", tag);
                cmd.Parameters.AddWithValue("@Surname", tbSurname.Text);
                cmd.Parameters.AddWithValue("@Name", tbName.Text);
                cmd.Parameters.AddWithValue("@Lived", tbLived.Text);
                cmd.Parameters.AddWithValue("@Birthplace", tbBirthplace.Text);
                cmd.Parameters.AddWithValue("@ShortInfo", tbShortInfo.Text);
                
                // должно быть 1
                int rowsInserted = cmd.ExecuteNonQuery();

                // должно быть 3 + 1 -> 4
                int after = (int)(new SqlCommand("SELECT COUNT(*) FROM Writers", conn).ExecuteScalar());

                // должно быть 1
                int withTag = (int)(new SqlCommand("SELECT COUNT(*) FROM Writers WHERE tag = " + tag, conn).ExecuteScalar());


            }
            finally
            {
                conn.Close();
                conn.Dispose();
            }