Why my rectangle is not drawing in a picturebox? (Dragging)

Question

So, I tried to do draw a rectangle by dragging my mouse in a form, and I was successful, but when I try to do the same way in a picturebox no rectangle is created.

Private Sub PictureBox1_MouseMove(sender As Object, e As MouseEventArgs) Handles PictureBox1.MouseMove

        If fGMouseIsDown And Not PictureBox1.Image Is Nothing Then

            rect.Width = e.X - rect.X
            rect.Height = e.Y - rect.Y
             Invalidate()


        End If
    End Sub

Private Sub PictureBox1_MouseDown(sender As Object, e As MouseEventArgs) Handles PictureBox1.MouseDown

        fGMouseIsDown = True
        rect.Location = e.Location
        rect.Width = 0
        rect.Height = 0
        Invalidate()
    End Sub 

Private Sub PictureBox1_Paint(sender As Object, e As PaintEventArgs) Handles PictureBox1.Paint

        e.Graphics.DrawRectangle(Pens.Blue, rect)

End Sub

Invalidating the form is not what you had in mind, make that PictureBox1.Invalidate(). And ensure you drag the right way, it can only work when you go from top-left to bottom-right. — Hans Passant, Sep 13 '19 at 14:03

score 2 · Accepted Answer · answered Oct 01 '19 at 03:51

Per @HansPassant: The Invalidate() call in your PictureBox1_MouseDown() method invalidates the form, when you instead want to invalidate the picture box.

That call should instead be:

PictureBox1.Invalidate()

Additionally, ensure you drag the right way; this will only work when you go from top-left to bottom-right.

Why my rectangle is not drawing in a picturebox? (Dragging)

1 Answers1