c＃如果bool不工作

Question

编辑：所以我猜对了投票，人们有问题再现问题？这对我来说并不难，复制我包含的代码，阅读原始预期和实际结果，运行程序，点击几下并拖动。我可以每次都重现这个。它并不重要，因为我解决了这个问题，但不得不等待它的回答。因此，如果持有这个保留的管理员可以删除帖子或标记我的答案作为答案，这将是伟大的。我提供了指南所概述的所有内容，以及＃34;最小代码＆＃34;的可能意见。它有所需的和实际的结果，重现的步骤，我不知道如何在不进行屏幕录制的情况下使其更清晰。如果你提出不同的意见，你实际上要求对某些事情作出澄清，以便我能看出错误。

原件：

我这里有一个有趣的问题。我试图在C＃中做一个简单的橡皮筋选择，除了一个奇怪的错误，如果我不做出选择，我就一切正常。

预期结果：MouseDown / MouseUp没有移动鼠标，移动鼠标后不应该选择。

实际结果：MouseDown / MouseUp没有移动鼠标，然后当我鼠标移动鼠标时，我移动鼠标时绘制选择。如果单击，选择将消失。然后，如果我再次单击并鼠标移动鼠标，则会不断重新绘制新选择。

我在表单中添加了一个标签来检查bool的状态。当我这样做时，一切都按预期工作。但是，一旦我注释掉label1.Text行，它就不再按预期工作了。我已经尝试添加多个bool来解决上述问题但无济于事。

那么除非我设置标签文本，为什么bool不被识别？附：我是C＃的新手，所以我欢迎任何批评。我从http://csharphelper.com/blog/2014/08/use-a-rubber-band-box-to-let-the-user-select-an-area-in-a-picture-in-c/

中提取了此代码

这是我目前的代码：

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 RubberBand
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }

        private Bitmap m_Orig = null;
        private int X0, X1, Y0, Y1;
        private bool sArea, isDown, hasMoved = false;
        private Bitmap sImg = null;
        private Graphics sGraph = null;

        private void Form1_Load(object sender, EventArgs e)
        {
            m_Orig = new Bitmap(pictureBox1.Image);
            this.KeyPreview = true;
        }

        private void Form1_KeyPress(object sender, KeyPressEventArgs e)
        {
            if (e.KeyChar == 27)
            {
                if (!sArea) return;
                sArea = false;
                isDown = false;
                hasMoved = false;

                sImg = null;
                sGraph = null;
                pictureBox1.Image = m_Orig;
                pictureBox1.Refresh();
            }
        }

        private void pictureBox1_MouseDown(object sender, MouseEventArgs e)
        {
            sArea = true;
            isDown = true;
            //label1.Text = isDown.ToString();
            X0 = e.X;
            Y0 = e.Y;

            sImg = new Bitmap(m_Orig);
            sGraph = Graphics.FromImage(sImg);
            pictureBox1.Image = sImg;
        }

        private void pictureBox1_MouseMove(object sender, MouseEventArgs e)
        {
            if (!sArea) return;
            hasMoved = true;
            //label1.Text = isDown.ToString();

            if (isDown)
            {
                X1 = e.X;
                Y1 = e.Y;

                sGraph.DrawImage(m_Orig, 0, 0);

                using (Pen select_pen = new Pen(Color.Red))
                {
                    select_pen.DashStyle = System.Drawing.Drawing2D.DashStyle.Dash;
                    Rectangle rect = MakeRectangle(X0, Y0, X1, Y1);
                    sGraph.DrawRectangle(select_pen, rect);
                }

                pictureBox1.Refresh();
            }
        }

        private void pictureBox1_MouseUp(object sender, MouseEventArgs e)
        {
            if (!sArea) return;
            if (!hasMoved) return;

            sArea = false;
            hasMoved = false;
            isDown = false;
            //label1.Text = isDown.ToString();
            sImg = null;
            sGraph = null;
            pictureBox1.Image = m_Orig;
            pictureBox1.Refresh();

            Rectangle rect = MakeRectangle(X0, Y0, X1, Y1);
            if ((rect.Width > 0) && (rect.Height > 0))
            {
                MessageBox.Show(rect.ToString());
            }
        }

        private Rectangle MakeRectangle(int x0, int y0, int x1, int y1)
        {
            return new Rectangle(
                Math.Min(x0, x1),
                Math.Min(y0, y1),
                Math.Abs(x0 - x1),
                Math.Abs(y0 - y1));
        }
    }
}

Answer 1

好的，经过更多的研究，这似乎是一个众所周知的问题。由于此页面，我已解决了我的问题：https://social.msdn.microsoft.com/Forums/vstudio/en-US/8e85eb78-77f2-485f-9bd3-3eaa44233a8a/mousedown-and-mousemove-events

以下是更新后的工作代码：

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 RubberBand
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }

        private Bitmap m_Orig = null;
        private int X0, X1, Y0, Y1;
        private bool sArea, hasMoved = false;
        private Bitmap sImg = null;
        private Graphics sGraph = null;

        private void Form1_Load(object sender, EventArgs e)
        {
            m_Orig = new Bitmap(pictureBox1.Image);
            this.KeyPreview = true;
        }

        private void Form1_KeyPress(object sender, KeyPressEventArgs e)
        {
            if (e.KeyChar == 27)
            {
                if (!sArea) return;
                sArea = false;
                hasMoved = false;

                sImg = null;
                sGraph = null;
                pictureBox1.Image = m_Orig;
                pictureBox1.Refresh();
            }
        }

        private void pictureBox1_MouseDown(object sender, MouseEventArgs e)
        {
            sArea = true;

            X0 = e.X;
            Y0 = e.Y;

            sImg = new Bitmap(m_Orig);
            sGraph = Graphics.FromImage(sImg);
            pictureBox1.Image = sImg;
        }

        private void pictureBox1_MouseMove(object sender, MouseEventArgs e)
        {
            if (e.Button == MouseButtons.Left)
            {
                if (!sArea) return;
                hasMoved = true;

                X1 = e.X;
                Y1 = e.Y;

                sGraph.DrawImage(m_Orig, 0, 0);

                using (Pen select_pen = new Pen(Color.Red))
                {
                    select_pen.DashStyle = System.Drawing.Drawing2D.DashStyle.Dash;
                    Rectangle rect = MakeRectangle(X0, Y0, X1, Y1);
                    sGraph.DrawRectangle(select_pen, rect);
                }

                pictureBox1.Refresh();
            }
        }

        private void pictureBox1_MouseUp(object sender, MouseEventArgs e)
        {
            if (!sArea) return;
            if (!hasMoved) return;

            sArea = false;
            hasMoved = false;

            sImg = null;
            sGraph = null;
            pictureBox1.Image = m_Orig;
            pictureBox1.Refresh();

            Rectangle rect = MakeRectangle(X0, Y0, X1, Y1);
            if ((rect.Width > 0) && (rect.Height > 0))
            {
                MessageBox.Show(rect.ToString());
            }
        }

        private Rectangle MakeRectangle(int x0, int y0, int x1, int y1)
        {
            return new Rectangle(
                Math.Min(x0, x1),
                Math.Min(y0, y1),
                Math.Abs(x0 - x1),
                Math.Abs(y0 - y1));
        }
    }
}