Drawing a line in Winforms
.net, c#, system.drawing, winforms
Solution
Hook up an event handler for the `Paint` event of the `GroupBox` and call `DrawLShapeLine` from within that event handler instead. You should then use the `Graphics` object supplied by in event arguments:
private void groupBox1_Paint(object sender, PaintEventArgs e)
{
DrawLShapeLine(e.Graphics, 10, 10, 20, 40);
}
As your code looks now it will attempt to paint in the `GroupBox` when the form requires painting. The group box may be painted at any other occasion, which will the line you paint disappear.
Problem
I am having trouble drawing a line within a group box in a simple windows form. here is my code: ``` public partial class Form1 : Form { public Form1() { InitializeComponent(); } protected override void OnPaint(PaintEventArgs e) { base.OnPaint(e); DrawLShapeLine(groupBox1.CreateGraphics(), 10, 10, 20, 40); } public void DrawLShapeLine(System.Drawing.Graphics g, int intMarginLeft, int intMarginTop, int intWidth, int intHeight) { Pen myPen = new Pen(Color.Black); myPen.Width = 2; // Create array of points that define lines to draw. int marginleft = intMarginLeft; int marginTop = intMarginTop; int width = intWidth; int height = intHeight; int arrowSize = 3; Point[] points = { new Point(marginleft, marginTop), new Point(marginleft, height + marginTop), new Point(marginleft + width, marginTop + height), // Arrow new Point(marginleft + width - arrowSize, marginTop + height - arrowSize), new Point(marginleft + width - arrowSize, marginTop + height + arrowSize), new Point(marginleft + width, marginTop + height) }; g.DrawLines(myPen, points); } } ``` If I attach the DrawLShapeLine method to a button click event, it draws fine, but it does not draw on load of the form. Please advice.