Question

我有一个链接到MySQL数据库的表单。我希望在表单上有3个 dateTimePickers 以允许三个日期，但是，如果没有选择一个，我希望该Picker显示为空白，而不是当前日期。

我正在使用以下代码，当我更改日期时，我收到错误“System.Windows.Forms.dll”中出现类型'System.StackOverflowException'的未处理异常选择器。

private void dateTimePicker1_ValueChanged(object sender, EventArgs e)
{
    if (txtdateTimePicker1.Text != "1/1/2000 12:00:00 AM")
    {
        dateTimePicker1.Format = DateTimePickerFormat.Short;
        dateTimePicker1.Text = txtdateTimePicker1.Text;
    }
    else
    {
        dateTimePicker1.Format = DateTimePickerFormat.Custom;
        dateTimePicker1.CustomFormat = " ";
        dateTimePicker1.Text = "";
    }
}

故障排除提示告诉我：确保没有无限循环或无限递归。

基本上，文本框 “txtdateTimePicker1” 在表单加载时填充日期值，如果它读取某个日期，则 “dateTimePicker1 “ 显示空值。

我认为循环发生是因为它查看 txtdateTimePicker1 的值，然后更改 dateTimePicker1 的值，从而导致它再次触发ValueChanged事件，但是我现在知道任何其他方式来正确触发事件。有没有办法使用While循环？有些话说：

While (txtdateTimePicker1.Text == "1/1/2000 12:00:00 AM")
{
    dateTimePicker1.Format = DateTimePickerFormat.Custom;
    dateTimePicker1.CustomFormat = " ";
    dateTimePicker1.Text = "";
}

但

if (txtdateTimePicker1.Text != "1/1/2000 12:00:00 AM")
{
    dateTimePicker1.Format = DateTimePickerFormat.Short;
    dateTimePicker1.Text = txtdateTimePicker1.Text;
}

我对While循环很新，我确实研究了一些，我知道它们如何工作，但我真的不知道语法。

或者...因为在初始化表单时填充了文本框，有没有办法可以触发代码我需要一种不同的方式？

此外，我知道我可能不会在这里使用最佳实践方法，这将在稍后出现。我需要尝试使其功能正常，除了这一个事件，我的表单的其余部分才能正常工作。请不要因为没有使用正确的方法而责备我，相反，请帮我解决手头的问题。

系统信息：

Windows 8.1
.NET Framework 4.5
Visual Studio 2013 Ultimate
MySQL 5.6 for Visual Studio

完整表单代码（减去MySQL连接字符串：）

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Forms;
using MySql.Data.MySqlClient;

namespace _2014BillOfMaterials
{
    public partial class BillofMaterialsRevisions : Form
    {
        public BillofMaterialsRevisions(string s)
        {
            if (s != "- Select a Job -")
            {
                string server = "192.168.1.149";
                string database = "####";
                string userid = "iuapp";
                string password = "iuapp";
                string str;
                str = "SERVER=" + server + ";" + "DATABASE=" + database + ";" + "UID=" + userid + ";" + "PASSWORD=" + password + ";";

                MySqlConnection con = null;

                con = new MySqlConnection(str);

                MySqlConnection myconn = new MySqlConnection(str);
                MySqlDataAdapter jobNumber = new MySqlDataAdapter("SELECT * FROM jobnumbers where jobNumber = '" + s + "'", myconn);

                DataTable dtJobNumber = new DataTable("jobnumbers");
                DataSet dtJobNumber2 = new DataSet();
                jobNumber.Fill(dtJobNumber);

                InitializeComponent();
                this.WindowState = FormWindowState.Maximized;

                MySqlDataAdapter adapter = new MySqlDataAdapter("SELECT * FROM jobnumbers where jobNumber = '" + s + "'", myconn);
                adapter.Fill(dtJobNumber2);
                textBox2.Text = dtJobNumber2.Tables[0].Rows[0][6].ToString();
                textBox1.Text = dtJobNumber2.Tables[0].Rows[0][8].ToString();
                textBox3.Text = dtJobNumber2.Tables[0].Rows[0][10].ToString();
                textBox4.Text = dtJobNumber2.Tables[0].Rows[0][0].ToString();

                txtdateTimePicker1.Text = dtJobNumber2.Tables[0].Rows[0][5].ToString();
                txtdateTimePicker2.Text = dtJobNumber2.Tables[0].Rows[0][7].ToString();
                txtdateTimePicker3.Text = dtJobNumber2.Tables[0].Rows[0][9].ToString();


                lblJobNumber.Text = s + " Revisions";
                label10.Text = s;
            }
            else
            {
                //Show Error MessageBox
                MessageBox.Show("Please Select a Job.", "Error", MessageBoxButtons.OK, MessageBoxIcon.Asterisk);
            }

        }

        private void BillofMaterialsRevisions_Load(object sender, EventArgs e)
        {
        }

        private void button1_Click(object sender, EventArgs e)
        {                        
            string server = "192.168.1.149";
            string database = "####";
            string userid = "iuapp";
            string password = "iuapp";
            string str;
            str = "SERVER=" + server + ";" + "DATABASE=" + database + ";" + "UID=" + userid + ";" + "PASSWORD=" + password + ";";

            MySqlConnection myconn2 = new MySqlConnection(str);
            MySqlConnection con = null;

            con = new MySqlConnection(str);
            con.Open();

            string date1 = dateTimePicker1.Value.ToString("yyyy-MM-dd");
            string date2 = dateTimePicker2.Value.ToString("yyyy-MM-dd");
            string date3 = dateTimePicker3.Value.ToString("yyyy-MM-dd");

            var cmd = new MySqlCommand("Insert into jobnumbers(id, jobNumber, IssuedDate, IssuedInitials, RevADate, RevAInitials, RevBDate, RevBInitials) SELECT DISTINCT '" +
                textBox4.Text + "', '" + 
                label10.Text + "', '" +
                date1 + "', '" +
                textBox2.Text + "', '" +
                date2 + "', '" +
                textBox1.Text + "', '" +
                date3 + "', '" +
                textBox3.Text +
                "' " +
                "ON DUPLICATE KEY UPDATE id =  '" + textBox4.Text + "' " +
                ", jobNumber = '" + label10.Text + "' " +
                ", IssuedDate = '" + date1 + "' " +
                ", IssuedInitials = '" + textBox2.Text + "' " +
                ", RevADate = '" + date2 + "' " +
                ", RevAInitials = '" + textBox1.Text + "' " +
                ", RevBDate = '" + date3 + "' " +
                ", RevBInitials = '" + textBox3.Text + "'", con);

            cmd.ExecuteNonQuery();
        }

        private void dateTimePicker1_ValueChanged(object sender, EventArgs e)
        {
            if (txtdateTimePicker1.Text == "1/1/2000 12:00:00 AM")
            {
                dateTimePicker1.Format = DateTimePickerFormat.Short;
                dateTimePicker1.Text = txtdateTimePicker1.Text;
            }
            else
            {
                dateTimePicker1.Format = DateTimePickerFormat.Custom;
                dateTimePicker1.CustomFormat = " ";
                dateTimePicker1.Text = "";
            }
        }

        private void dateTimePicker2_ValueChanged(object sender, EventArgs e)
        {
            if (txtdateTimePicker2.Text != "" || txtdateTimePicker2.Text != "1/1/2000 12:00:00 AM")
            {
                dateTimePicker2.Format = DateTimePickerFormat.Short;
                dateTimePicker2.Text = txtdateTimePicker2.Text;
            }
            else
            {
                dateTimePicker2.Format = DateTimePickerFormat.Custom;
                dateTimePicker2.CustomFormat = " ";
                dateTimePicker2.Text = "";
            }
        }

        private void dateTimePicker3_ValueChanged(object sender, EventArgs e)
        {
            if (txtdateTimePicker3.Text != "" || txtdateTimePicker3.Text != "1/1/2000 12:00:00 AM")
            {
                dateTimePicker3.Format = DateTimePickerFormat.Short;
                dateTimePicker3.Text = txtdateTimePicker3.Text;
            }
            else
            {
                dateTimePicker3.Format = DateTimePickerFormat.Custom;
                dateTimePicker3.CustomFormat = " ";
                dateTimePicker3.Text = "";
            }
        }
    }
}

Answer 1

不允许将"" (Empty)设置为Text属性，因为Text属性应该是有效的 DateTime对象。查看其documentation。

解决此问题的可能性是禁用DateTimePicker控件并在需要时将其启用。

使用：

dateTimePicker1.Enabled = True;  // enables it
dateTimePicker1.Enabled = False; // disable it

希望它有所帮助！

Answer 2

我所做的是创建了一个Checkbox，它更改了dateTimePicker和相关textBoxes的CustomFormat属性和Text Value，并且我已经将我的数据库中字段的数据类型从DATE更改为Varchar，这似乎正常工作。此特定应用程序必须以某种方式工作，并且这些表不会用于需要日期为特定数据类型的大量报表。

我意识到还有很多其他更好的方法可以实现这一目标，但是我有点时间限制，所以现在这样做。

NeverHopeless给了我一个解决方案，在不同情况下会有效，但对于这个项目来说，这还不够。

以下是Checkboxes的代码：

public void CheckCheckBoxes2()
{
    if (checkBox2.Checked == false)
    {
        dateTimePicker2.Format = DateTimePickerFormat.Custom;
        dateTimePicker2.CustomFormat = " ";
        dateTimePicker2.Text = null;
        dateTimePicker2.Enabled = false;
        textBox2.Text = null;
        textBox2.Enabled = false;
    }
    else
    {
        dateTimePicker2.Format = DateTimePickerFormat.Short;
        dateTimePicker2.Enabled = true;
        textBox2.Enabled = true;
    }
}

如果TextBox是特定值，则将dateTimePicker设置为Null

系统信息：

完整表单代码（减去MySQL连接字符串：）

2 个答案: