C＃鼠标事件序列

Question

Question... why does this code only produce a message box "Down"? I'm not getting the Up. If I block down code, the up works.

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;

namespace Mouse
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }   
        private void Form1_MouseUp(object sender, MouseEventArgs e)
        {
           MessageBox.Show("Up");                     
        }
        private void Form1_MouseDown(object sender, MouseEventArgs e)
        {
           MessageBox.Show("Down");
        }     
    }
}

Answer 1

Because you are showing a MessageBox

Whenever a mouse down event happened a MessageBox will popup. The MessageBox Will be in foreground and the up event will be on the MessageBox instead of the form. Thus the up event in the form doesn't fire

Just do a Console.WriteLine instead of MessageBox and it should work as expected

Answer 2

They will both fire if you remove the message box call. this is interferring with the mouse events because your loosing focus on the form. Instead of using message box try using...

  Console.WriteLine("MouseUp"); 

This will display in the ouput window and not interfere with the events