How do I detect click on a line in Windows Forms

Question

I have a winforms application

Here is my code

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using S         


        

Answer 1

I implemented a simple Line class to check if a dot fall on the line.
You can capture a mouse position out of Form_Click event

Here's the snippet

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Windows.Forms;

namespace WindowsFormsApplication
{
    public partial class Form1 : Form
    {
        Line myLine;
        int x1 = 10;
        int x2 = 40;
        int y1 = 0;
        int y2 = 30;
        public Form1()
        {
            InitializeComponent();
            myLine = new Line() { Start = new Point(x1, y1), Stop = new Point(x2, y2), Epsilon = 10 };
        }

        private void Form1_Paint(object sender, PaintEventArgs e)
        {
            Pen pen = new Pen(Color.FromArgb(255, 0, 0, 0));
            e.Graphics.DrawLine(pen, x1, y1, x2, y2);
            pen.Dispose();
        }

        private void Form1_Click(object sender, EventArgs e)
        {
            MouseEventArgs me = (MouseEventArgs)e;
            bool contain = myLine.contain(new Point(me.X,me.Y));
        }
    }

    public class Line
    {
        public Point Start { get; set; }
        public Point Stop { get; set; }
        public float Epsilon { get; set; }

        public bool contain(Point p)
        {
            // y = mx + c
            float m = (Stop.Y - Start.Y) / (Stop.X - Start.X);
            float c = Stop.Y - (m * Stop.X);
            return p.X >= Math.Min(Start.X, Stop.X)
                && p.X <= Math.Max(Start.X, Stop.X)
                && p.Y >= Math.Min(Start.Y, Stop.Y)
                && p.Y <= Math.Max(Start.Y, Stop.Y)
                && Math.Abs(Math.Abs(p.Y) - Math.Abs((m * p.X) + c)) < epsilon; //with relax rules
                //&& (p.Y == (m*p.X)+c); // strict version
        }
    }

UPDATE
careful of a case where X1 == X2. It will throw exception.