How initialize AForge webcam

Question

I try to write a small peace of code to capture a frame using Aforge I made a reference to Aforge.dll and AForge.Video.DirectShow.dll The code is below, but i am doing something wrong. The Warning i get "the name videoDevices does not exist in the current context. I think it has to do about where i try to create that variable but i'm not exactly sure as where to place that code of the button to get it initialized. The error is displayed in visual studio also as a redline under the object "videoDevices"

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;
using AForge;
using AForge.Video.DirectShow;

namespace AforgeCam
 {
   public partial class Form1 : Form
 {
    public Form1()
    {
        InitializeComponent();

    }

    private void button1_Click(object sender, EventArgs e)
    {

        videoDevices = new FilterInfoCollection(FilterCategory.VideoInputDevice);

        if (videoDevices.Count == 0)
            throw new ApplicationException();

        foreach (FilterInfo device in videoDevices)
        {
    VideoCaptureDevice videoSource = new    VideoCaptureDevice(device.MonikerString);
            videoSource.DesiredFrameSize = new Size(320, 240);
            videoSource.DesiredFrameRate = 15;
            videoSourcePlayer1.VideoSource = videoSource;
            videoSourcePlayer1.Start();
        }

    }
    }
}

Answer 1

As requested the solution is below , the code works, i will raise a new question for another question i have about it. the code requires a dropdown box, 2 buttons and a picturebox

using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Windows.Forms;
using AforgeCam;
using AForge.Video;
using AForge.Video.DirectShow;

namespace AforgeCam
{
public partial class Form1 : Form
{
private FilterInfoCollection VideoCaptureDevices;
private VideoCaptureDevice FinalVideo;

public Form1() // init
{
    InitializeComponent();
    {
        VideoCaptureDevices = new FilterInfoCollection(FilterCategory.VideoInputDevice);
        foreach (FilterInfo VideoCaptureDevice in VideoCaptureDevices)
        {
            comboBox1.Items.Add(VideoCaptureDevice.Name);
        }
        comboBox1.SelectedIndex = 0;
    }
}

private void button1_Click(object sender, EventArgs e)
{
    FinalVideo = new VideoCaptureDevice(VideoCaptureDevices[comboBox1.SelectedIndex].MonikerString);
    FinalVideo.NewFrame += new NewFrameEventHandler(FinalVideo_NewFrame);
    FinalVideo.Start();
}

void FinalVideo_NewFrame(object sender, NewFrameEventArgs eventArgs)
{
    Bitmap video = (Bitmap)eventArgs.Frame.Clone();
    pictureBox1.Image = video;

}

private void button2_Click(object sender, EventArgs e)
{
    FinalVideo.Stop();
}
}