PaintEventArgs e showing null reference

S J

public void Paint(PaintEventArgs e) //here e is showing null reference in class {"Object reference not set to an instance of an object."}//
{
//Graphics g = e.Graphics;
e.Graphics.DrawRectangle(pen1, rect);
}

how to avoid this I need to draw a rectangle by using class method but when I call paint method showing null reference exception.

4 Replies

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S J5y ago
Now i have another new problem
if two rectangles are not intersecting, then also 2nd one rectangle is filling with color why so i am not getting anybody help me.

Pen pen1 = new Pen(displayclass.boardercolor, 2);
displayclass.brush = new SolidBrush(displayclass.intrcolor);
rect = new Rectangle(displayclass.xCoordinate, displayclass.yCoordinate, displayclass.rectWidth, displayclass.rectHeight);
Rectangle rect2;
rectanglelist.Add(rect);
penlist.Add(pen1);
//rectangle.Add(pen1, rect);
for (int j = 0; j < rectanglelist.Count;j++ )
//foreach (Rectangle iteam in rectanglelist)
{
if (rectanglelist.Count > 1)
{
//if (rect.Left == iteam.Value.Left && rect.Right == iteam.Value.Right)
//{
// Graphics g1 = e.Graphics;
// g1.DrawRectangle(iteam.Key, iteam.Value);
// //g1.FillRectangle(brush, rect2);
// continue;
//}
if (rect.IntersectsWith(rectanglelist[j])) //If 2nd rectangle is not going to intersect means then also it is filling color
{
rect2 = Rectangle.Intersect(rect, rectanglelist[j]);
if (!rect2.IsEmpty)
{
brushlist.Add(displayclass.brush);
Intersectedrectanglelist.Add(rect2);
}
}
if (Intersectedrectanglelist.Count > 0)
{
for (int i = 0; i < Intersectedrectanglelist.Count(); i++)
{
e.Graphics.FillRectangle(brushlist[i],Intersectedrectanglelist[i]);
}
//continue;
}
}
//using (pen1 = new Pen(displayclass.boardercolor, 2))
//{
// Graphics g = e.Graphics;
// g.DrawRectangle(penlist[j], rectanglelist[j]);
//}
Graphics g = e.Graphics;
g.DrawRectangle(penlist[j], rectanglelist[j]);
}

}
+2
S J5y ago
i am using classform, so in class can't access UI controls na so i tried for manual painevents at that time its shown e null.
Thanku @sachin,Salaman for your answer, that one i resolved .
+2
Sachin Singh5y ago
Why do you need PaintEventArgs when all you need is a Graphics object?as per your code you need to pass PaintEventArgs like below
public void pr_picturebox_refresh()
{
    Graphics g = picturebox1.CreateGraphics();
    picturebox1.Refresh();
    Rectangle r= new Rectangle(0, 0, picturebox1.Width, picturebox1.Height);
    PaintEventArgs pp = new PaintEventArgs(g, r);
    picturebox1_Paint_manual(picturebox1, l_pe_work);
}

private void Paint(PaintEventArgs e)
{
    Rectangle rect = new Rectangle(10, 10, 50, 40);

    using (Pen pen = new Pen(Color.Red, 1))
    {
        e.Graphics.DrawRectangle(pen, rect);
    }
}
+3
Salman Beg5y ago
Hey when you are calling Paint method then at that time you need to pass PaintEventArgs also otherwise during the access of methods it will show null reference exception. Thanks
+3