c# - 如何删除表格上的画线？

Question

实际上，关于这个主题有一些类似的问题，但我看不到我正在寻找的答案。

例如，我在 windows 窗体上画了两条线，我想删除其中一条并保留另一条，我该怎么做？

this.Invalidate();或Graphics.Clear();清除所有表格，我不想要这个，我想删除特定行。您还有其他解决方案吗？

Answer 1

以下将按时间倒序删除所有创建的行。

    Graphics g;
    Pen p;
    Bitmap bmp;
    List<Point> Lines = new List<Point>();

    private void Form2_Load(object sender, EventArgs e)
    {
        bmp = new Bitmap(Width, Height, System.Drawing.Imaging.PixelFormat.Format24bppRgb);
        BackgroundImage = bmp;
        g = Graphics.FromImage(BackgroundImage);
        g.Clear(Color.DeepSkyBlue); //This is our backcolor
    }

    private void btnLine1_Click(object sender, EventArgs e)
    {
        Point A = new Point(50, 50);
        Point B = new Point(100, 50);
        p = new Pen(Color.Red);
        g.DrawLine(p, A, B); //Use whatever method to draw your line
        Lines.Add(A); //Grab the first point; add to list
        Lines.Add(B); //Grab the second point; add to list
        Refresh(); //Refresh drawing to bitmap.
    }

    private void btnDrawLine2_Click(object sender, EventArgs e)
    {
        Point A = new Point(50, 60);
        Point B = new Point(100, 60);
        p = new Pen(Color.White);
        g.DrawLine(p, A, B); //Same logic as above
        Lines.Add(A);
        Lines.Add(B);
        Refresh();
    }

    private void btnUndo_Click(object sender, EventArgs e)
    {
        c = new Pen(Color.DeepSkyBlue);
        r = new Pen(lastColor.ElementAt(lastColor.Count - 2));
        try
        {
            g.DrawLine(c, Lines.ElementAt(Lines.Count - 2), Lines.ElementAt(Lines.Count - 1));
            Lines.RemoveAt(Lines.Count - 2);
            Lines.RemoveAt(Lines.Count - 1);
            for (int i = Lines.Count; i > 0; i--)
            {
            g.DrawLine(r, Lines.ElementAt(Lines.Count - 2), Lines.ElementAt(Lines.Count - 1));
            }
        }
        catch { }
        Refresh();
    }

这是并排的2行：

这里有 2 行重叠：

*记得处置你的图形对象！