Question

C#在pictureBox控件上画的直线被其他窗口挡一下，直线就被擦除掉，要重新画。

怎么可以解决这样的问题，即使被挡住，画的线都还在的。

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Answer 1

方法1：写在Paint事件中，这样就不会消失在PictureBox中。

方法2：绘制到图形对象里，而不是简单是用画笔画线
看下面的代码，s_Bmp可以持久显示，s_pen则不行,
不好意思我这是vb.net代码，道理一样，不难看懂...
private sub s_Bmp()
Dim Bmp As Bitmap
Dim Gra As Graphics

Dim Pen As New Pen(Color.White)

Bmp = New Bitmap(PictureBox1.Width, PictureBox1.Height)

Gra = Graphics.FromImage(Bmp)

Dim Dia As Single = Math.Min(PictureBox1.Height, PictureBox1.Width) * 0.5!

Gra.DrawArc(Pen, (PictureBox1.Width - Dia) / 2.0!, (PictureBox1.Height - Dia) / 2.0!, Dia, Dia, 0, 360)

Gra.DrawLine(Pen, 0, 0, PictureBox1.Width / 2.0!, PictureBox1.Height / 2.0!)

PictureBox1.Image = Bmp

end sub

private sub s_Pen()
Dim Gra As Graphics = PictureBox1.CreateGraphics()
Dim Pen As New Pen(Color.Magenta)

Dim Dia As Single = Math.Min(PictureBox1.Height, PictureBox1.Width) * 0.5!

Gra.DrawRectangle(Pen, (PictureBox1.Width - Dia) / 2.0!, (PictureBox1.Height - Dia) / 2.0!, Dia, Dia)

end sub