Bitmap Define problem

i am trying to learn emguCV --

using System;

using System.Collections.Generic;

using System.ComponentModel;

using System.Data;

using System.Drawing.Printing;

using System.Drawing;

using System.Drawing.Drawing2D;

using System.Drawing.Imaging;

using System.IO;

using System.Linq;

using System.Text;

using System.Threading.Tasks;

using System.Windows.Forms;

using Emgu.CV;

using Emgu.CV.Structure;

namespace WindowsFormsApp1

{

public partial class Form1 : Form

{

Image imgInput;

public Form1()

{

InitializeComponent();

}

private void button1_Click(object sender, EventArgs e)

{

OpenFileDialog dialog = new OpenFileDialog();

if (dialog.ShowDialog() == DialogResult.OK)

{

imgInput = new Image(dialog.FileName);

pictureBox1.Image = imgInput.Bitmap;

}

But they will not define my bitmap what i do wrong=?