openCV/OpenCV/Form1.cs

using System;
using System.Windows.Forms;
using OpenCvSharp;

namespace OpenCV
{
    public partial class Form1 : Form
    {
        CvCapture capture;
        IplImage src;

        string filePath;
        int frameCount = 0;

        public Form1()
        {
            InitializeComponent();
        }

        private string FindFileName()
        {
            string path = "";

            OpenFileDialog dialog = new OpenFileDialog();
            DialogResult dialogResult = dialog.ShowDialog();
            if (dialogResult == DialogResult.OK)
                path = dialog.FileName;

            return path;
        }

        private void Form1_Load(object sender, EventArgs e)
        {
            try
            {
                //capture = CvCapture.FromCamera(CaptureDevice.DShow, 0);
                //capture.SetCaptureProperty(CaptureProperty.FrameWidth, 640);
                //capture.SetCaptureProperty(CaptureProperty.FrameHeight, 480);
                filePath = FindFileName();
                if (String.IsNullOrEmpty(filePath))
                    return;

                capture = CvCapture.FromFile(filePath);
                timer1.Enabled = true;
            }
            catch (Exception ex)
            {
                timer1.Enabled = false;
                MessageBox.Show(ex.Message);
            }
        }

        private void timer1_Tick(object sender, EventArgs e)
        {
            frameCount++;
            label1.Text = $"Frame: {frameCount} / {capture.FrameCount}";
            src = capture.QueryFrame();
            if (frameCount == capture.FrameCount)
            {
                frameCount = 0;
                capture = CvCapture.FromFile(filePath);
            }

            pictureBoxIpl1.ImageIpl = src;
        }

        private void Form1_FormClosing(object sender, FormClosingEventArgs e)
        {
            Cv.ReleaseImage(src);
            if (src != null)
                src.Dispose();
        }
    }
}