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c# - 无法将类型 'string' 隐式转换为 'System.DateTime' - 使用 t

问题描述

如下所示，该错误源于我认为从 Visual Basic 转换为 C# 之间的错误。我不知道这是否是与 VB 的不正确/过时链接，或者我正在“转换”为时间值的“字符串”。在我是否必须更改 if-then 语句的结构方面需要帮助。

using System;
using System.Media;
using System.Windows.Forms;

namespace NotificationDemo
{
    public partial class NotificationDemo : Form
    {
        public NotificationDemo()
        {
            InitializeComponent();
        }

        // Variables //

        public int hour;
        public int minute;

        // Messaging System //
        public void Alert(string msg)
        {
            NotifyForm frmn = new NotifyForm();
            frmn.showAlert(msg);
        }
        private void BtnNotify_Click(object sender, EventArgs e)
        {
            this.Alert("Default Message");

            SoundPlayer player = new SoundPlayer();
            player.SoundLocation = @"C:\Windows\Media\Alarm03.wav";
            player.Play();
        }

        // Basic Schedule SysFunction 

        public string currenttime;
        public string messagetime;

        private void timer1_Tick(object sender, EventArgs e)
        {
            currenttime = DateTime.Now.ToString("hh:mm:ss tt");
            label1.Text = currenttime; 
        }

        private void timer2_Tick(object sender, EventArgs e)
        {
            messagetime = maskedTextBox1.Text + " " + comboBox1.Text;

            if (currenttime == messagetime)
            {
                timer2.Stop();
                this.Alert(textBox1.Text);
                button1.Enabled = true;
                button2.Enabled = false;

                SoundPlayer player = new SoundPlayer();
                player.SoundLocation = @"C:\Windows\Media\Alarm03.wav";
                player.Play();
            }
        }

        private void button1_Click(object sender, EventArgs e)
        {
            timer2.Start();
            button1.Enabled = false;
            button2.Enabled = true;
        }

        private void button2_Click(object sender, EventArgs e)
        {
            timer2.Stop();
            button1.Enabled = true;
            button2.Enabled = false;

        }

        // Advanced Schedule SysFunction

        public ProgramFunctionsDataContext doAction = new ProgramFunctionsDataContext();


        private void NotificationDemo_Load(object sender, EventArgs e)
        {
            // // Basic Component

            int hour = 1;
            int minute = 1;

            for (this.hour = hour; hour <= 12; hour++)
            {
                cbhour.Items.Add(hour);
            }

            for (this.minute = minute; minute <= 59; minute++)
            {
                cbminute.Items.Add(minute);
            }

            // Appointment Check

            foreach (var app in doAction.AppointmentSets)
            {
///LINE OF ERROR
                if (app.AppointmentDate = DateTime.Today.ToLongDateString())
///LINE OF ERROR
                {
                    
                }
            }
        }
    }
}

标签： c#vb.netvb.net-to-c#

解决方案

这是由于您正在使用=which 是分配值的运算符

相反，您需要使用==对if语句进行比较

更新：由于@Llama担心以前的解决方案会导致转换错误并且我误解了错误消息，因此可以使用以下两种解决方案：

方案一：直接根据Date比较

if (app.AppointmentDate.Date == DateTime.Today.Date)

解决方案 2：将string格式中的日期与 on进行比较ToLongDateString()

if (app.AppointmentDate.ToLongDateString() == DateTime.Today.ToLongDateString())

解决方案 1 将是首选，因为它更简单并且与解决方案 2 完全相同

在进行比较时，如果将其转换为格式，请确保使用的两个值必须是相同的数据类型和Date字符串String格式。

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