Question

I have a pictureBox with an image inside.
I want, when i click on a button the image should hide and click again to show the image.

In the pictureBox, using paint event i am drawing some lines.
So if im doing pictureBox1.Refresh(); it will draw the lines. I want that if i click on a button the image will not display on/off.

pictureBox1 = null; or pictureBox1.Image.Dispose(); doesn’t work it’s showing me big red x with white background.

Answer 1

For toggling the image in your PictureBox you can create a 1 pixel bitmap and assign it to the picture box when you want hide your image, then assign your image back again. I am a little unclear of what the second part of your question is asking, any drawing in the picturebox’s Paint Event will remain unless you exclude it in the Paint Event based on some Condition. If you want to draw a line in the box an toggle it on/off from a button see my second example.

i.e.

public partial class Form1 : Form
{
    Bitmap nullBitmap = new Bitmap(1, 1); // create a 1 pixel bitmap
    Bitmap myImage = new Bitmap("Load your Image Here"); // Load your image
    bool showImage;  // boolean variable so we know what image is assigned
    public Form1()
    {
        InitializeComponent();
        pictureBox1.Image = myImage;
        showImage = true;
    }

    private void button1_Click(object sender, EventArgs e)
    {
        if (showImage)
        {
            pictureBox1.Image = nullBitmap;
            showImage = false; 
        }
        else
        {
            pictureBox1.Image = myImage;
            showImage = true;
        }
    }
}

Second Example

public partial class Form1 : Form
{
    bool showLines;
    public Form1()
    {
        InitializeComponent();
        showLines = true;
    }

    private void button1_Click(object sender, EventArgs e)
    {
        if (showLines)
        {
            showLines = false;
            pictureBox1.Invalidate();
        }
        else
        {
            showLines = true;
            pictureBox1.Invalidate();
        }
    }

    private void pictureBox1_Paint(object sender, PaintEventArgs e)
    {
        if(showLines)
            e.Graphics.DrawLine(Pens.Purple, 0, 0, 100, 100);
    }
}