请教datetime类型插入数据库
string 登记时间 = dateTimePicker1.Value.ToString();
DateTime dt = Convert.ToDateTime(登记时间);
string connstr = "server=.;database=hotelsql;integrated security=true";
SqlConnection mycon = new SqlConnection(connstr);
mycon.Open();
string myinsert = "insert into 预订单(客户姓名,客户身份证号,联系电话,房间号,房间类型,押金,预订时间)values ('" + textBox5.Text + "','" + textBox6.Text + "','" + textBox7.Text + "','" + textBox1.Text + "','" + textBox3.Text + "','" + textBox4.Text + "','dt')";
SqlCommand mycom = new SqlCommand(myinsert, mycon);
mycom.ExecuteNonQuery();
mycon.Close();
MessageBox.Show("已成功向数据库表中插入一条记录!");
为什么系统总是提示转换datetime错误呢