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I want to a line between two points using mouse move and second time
I click the mouse, a line will be draw and start drawing new line. I've tried use g.clear(backcolor) and refresh(), but when every time I move the mouse the lines appear and disappear. How I can solve this problem?

What I have tried:

namespace projebaslangıcLine2
{
public partial class Form1 : Form
{

private bool mouse_is_down = false;
private bool key_space = false;
private bool line_selected = false;
List<point> start_points;
List<point> finish_points;
private Point start;
private Point finish;
Graphics g;

public Form1()
{
InitializeComponent();
BackColor = Color.Black;
g = CreateGraphics();
start_points = new List<point>();
finish_points = new List<point>();

}

private void Form1_Load(object sender, EventArgs e)
{

}

private void Form1_MouseDown(object sender, MouseEventArgs e)
{
if (line_selected == true && start.X == 0)
{
mouse_is_down = true;
start.X = e.X;
start.Y = e.Y;

}
else
{
finish.X = e.X;
finish.Y = e.Y;
start_points.Add(start);
finish_points.Add(finish);

Invalidate();
start.X = e.X;
start.Y = e.Y;
}

}

private void Form1_MouseMove(object sender, MouseEventArgs e)
{

if (mouse_is_down == true && line_selected == true)
{
g.Clear(BackColor);
g.DrawLine(Pens.White, start, new Point(e.X,e.Y));
silenenleri_ciz();

}

}

private void Form1_Paint(object sender, PaintEventArgs e)
{
using (var p = new Pen(Color.White))
{
for (int x = 0; x < start_points.Count; x++)
{
g.DrawLine(p, start_points[x], finish_points[x]);

}
}
}

private void silenenleri_ciz()
{

for (int x = 0; x < start_points.Count; x++)
{

g.DrawLine(new Pen(Color.White), start_points[x], finish_points[x]);
}
}

private void Form1_KeyDown(object sender, KeyEventArgs e)
{
if (e.KeyCode == Keys.Space)
{
key_space = true;
}
if (key_space == true && e.KeyCode == Keys.L)
{

mouse_is_down = false;
secilenKomut.Text = "Line";
line_selected = true;

}

}

private void Form1_KeyUp(object sender, KeyEventArgs e)
{
key_space = false;
}

private void secilenKomut_TextChanged(object sender, EventArgs e)
{

}

private void secilenKomut_Click(object sender, EventArgs e)
{
secilenKomut.TabStop = true;
}

}
}
Posted
Updated 2-Feb-19 5:19am
Comments
Gerry Schmitz 3-Feb-19 22:02pm
   
Why are you using "mouse move"? You only need 2 points (i.e. "clicks") to draw a line.
Member 14125168 5-Feb-19 7:09am
   
Because I want to see angle of line by mouse move

1 solution

You should do all drawing inside in overload of the form's OnPaint method. See Control.OnPaint(PaintEventArgs) Method (System.Windows.Forms) | Microsoft Docs[^].
   
Comments
Maciej Los 3-Feb-19 16:33pm
   
5ed!

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