日期以全零形式输入数据库，但应用程序显示正确的日期

我的应用程序应该将来自职员的简单数据输入数据库，它确实这样做了。

也就是说，但是，日期输入不正确，我看不出原因。

消息框显示"日期对象"值。

我的表格如下：

CREATE TABLE `SALES` (
  `salesDate` date NOT NULL,
  `taxable` decimal(10,2) DEFAULT NULL,
  `untaxable` decimal(10,2) DEFAULT NULL,
  `tax` decimal(10,2) DEFAULT NULL,
  `customerName` varchar(52) DEFAULT NULL,
  `customerPhone` varchar(12) DEFAULT NULL,
  `warranty` int(11) DEFAULT NULL,
  `description` varchar(255) DEFAULT NULL
)

是否存在导致日期全部为零的问题？我得到的只是这样的数据(从数据库复制(

INSERT INTO `SALES` VALUES('0000-00-00', 65.00, 65.00, 3.90, '9984', '987987', 987987, '987987');

在应用程序端，提交按钮的事件处理程序如下所示：

        private void btn_Submit_Click(object sender, EventArgs e)
    {
        if (isValidData() && isPresent(rTxt_Description, "Description"))
        {
            //CONVERT FORM VALUES AND STORE IN VARIABLES TO SEND TO MYSQL QUERY
            DateTime saleTime = saleDatePicker.Value;
            string date = saleTime.ToString("MM/dd/yyyy");
            MessageBox.Show(date, date);
            Decimal untaxable = Convert.ToDecimal(txt_Untaxable.Text);
            Decimal taxable = Convert.ToDecimal(txt_Taxable.Text);
            Decimal tax = Convert.ToDecimal(txt_Tax.Text);
            string customerName = txt_CustomerName.Text;
            string customerPhone = txt_CustomerPhone.Text;
            string description = rTxt_Description.Text;
            // Create the query using parameter placeholders, not the actual stringized values....
            string query = "INSERT into SALES VALUES (@stime, @taxable, @untaxable, @tax, @cname, @cphone, @warranty, @desc)";
            // Create a list of parameters with the actual values with the placeholders names
            // Pay attention to the Size value for string parameters, you need to change it 
            // accordingly to your fields size on the database table.
            List<MySqlParameter> prms = new List<MySqlParameter>()
            {
                new MySqlParameter {ParameterName="@stime", MySqlDbType=MySqlDbType.Date, Value =  date },
                new MySqlParameter {ParameterName="@taxable", MySqlDbType=MySqlDbType.Decimal, Value =  taxable },
                new MySqlParameter {ParameterName="@untaxable", MySqlDbType=MySqlDbType.Decimal, Value =  untaxable },
                new MySqlParameter {ParameterName="@tax", MySqlDbType=MySqlDbType.Decimal, Value =  tax },
                new MySqlParameter {ParameterName="@cname", MySqlDbType=MySqlDbType.VarChar, Value =  customerName, Size = 150 },
                new MySqlParameter {ParameterName="@cphone", MySqlDbType=MySqlDbType.VarChar, Value = customerPhone , Size = 150 },
                new MySqlParameter {ParameterName="@warranty", MySqlDbType=MySqlDbType.Int32, Value = customerPhone , Size = 150 },
                new MySqlParameter {ParameterName="@desc", MySqlDbType=MySqlDbType.VarChar, Value = description , Size = 950 }
            };
            // Pass query and parameters to the insertion method.
            insertValues(query, prms);

连接是这样建立的：

private void insertValues(string q, List<MySqlParameter> parameters)
{
    using (MySqlConnection con = new MySqlConnection("My Connection String"))
    using (MySqlCommand cmd = new MySqlCommand(q, con))
    {
        con.Open();
        cmd.Parameters.AddRange(parameters.ToArray());
        int rowsInserted = cmd.ExecuteNonQuery();
        //return rowsInserted;
    }
}

            DateTime saleTime = saleDatePicker.Value;
        string date = saleTime.ToString("MM/dd/yyyy");

string date = saleTime.ToString("yyyy-MM-dd");