C#button判断三个textbox不为空则insert数据，每次都是插入2行，和解？

       if    (textBox2.Text.Length > 0 & textBox3.Text.Length>0&textBox4.Text.Length > 0)
            {
                cn.Open();
                cmd.Connection = cn;
                cmd.CommandText = (“insert into 部门基本信息表  values (“”” + textBox2.Text.Trim() + “””,””” + textBox3.Text.Trim() + “””,””” + textBox4.Text.Trim() + “””) “);
                cmd.ExecuteNonQuery();
                int i = cmd.ExecuteNonQuery();
                if (i > 0)
                {
                    MessageBox.Show(“新增成功”, “提示”);
                }
                else
                {
                    MessageBox.Show(“新增失败”, “提示”);
                }
                cn.Close();
                                           }
                 else 
            {
                MessageBox.Show(“新增信息不全”, “提示”);
                
            cn.Close();

每次三个textbox写入数据后点击新增都会插入重复的两行，搞不明白，新手菜鸟。请多赐教！