C# WebCam with .dll wrapper

John Luciani

I am trying to integrate a webcam into a fitness tracking program I have made for persons with disabilities, specifically down syndrome. I need to make it as simple as possible for someone to come up, select take a picture and the form pops up, etc...

Below is the code I am using to implement the wrapper found in this article: http://www.c-sharpcorner.com/uploadfile/yougerthen/integrate-the-web-webcam-functionality-using-C-Sharp-net-and-com-part-viii/

I have implemented as stated. The program will run but my buttons do not do anything when clicked. Am I missing something?

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 WebCamera;

namespace WindowsFormsApplication2

{

public partial class Form1 : Form

{

public Form1()

{

InitializeComponent();

}

private void pictureBox1_Click(object sender, EventArgs e)

{

pictureBox1.Image = null;

}

private void Form1_Load(object sender, EventArgs e)

{

oWebCam = new WebCamera.WebCam();

oWebCam.Container = pictureBox1;

}

WebCam oWebCam;

private void btnStart_Click(object sender, EventArgs e)

{

oWebCam.OpenConnection();

}

private void btnSave_Click(object sender, EventArgs e)

{

oWebCam.SaveImage();

}

private void btnStop_Click(object sender, EventArgs e)

{

oWebCam.Dispose();

}

private void Form1_Load_1(object sender, EventArgs e)

{

}

private void btnStart_Enter(object sender, EventArgs e)

{

Button b = (Button)sender;

b.BackColor = Color.Red;

}

private void btnStart_Leave(object sender, EventArgs e)

{

Button b = (Button)sender;

b.BackColor = Color.Gray;

}

Else Everything is the same as the above example. The form loads but the buttons do not do anything.

4 Replies

Know the answer? Post it — somebody with the same question will find it here.

Vulpes14y ago
Accepted answer
It may be that these two handlers aren't wired up either:

private void pictureBox1_Click(object sender, EventArgs e)
{
pictureBox1.Image = null;
}

private void Form1_Load(object sender, EventArgs e)
{
oWebCam = new WebCamera.WebCam();
oWebCam.Container = pictureBox1;
}

If Form1_Load is never executed, then oWebCam will still be null which would explain the error.

You can check again using a MessageBox.Show and, if you find that they're not wired up, add these two lines to the others in the constructor:

this.Load += Form1_Load;
pictureBox1.Click += pictureBox1_Click;

For future reference, tThe best way to ensure that events are wired up is to add the skeleton handlers from the Visual Studio form designer. In the case of the Click event, all you need to do is to double-click the buttons themselves in the designer and a skeleton eventhandler will be created into which you can insert your code.

Whenever you use the designer in this way (or by adding eventhandlers from the Properties Box), then VS inserts code similar to the above in your InitializeComponent() method, so you don't need to worry about doing it manually.
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John Luciani14y ago
Fantastic!!! Thanks for all the help!
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John Luciani14y ago
The did work! Thanks!! Now I get an error of: NullReference Exception was unhandled at the line for oWebCam.OpenConnection();
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Vulpes14y ago
If you've simply copied this code from the article:

private void btnStart_Click(object sender, EventArgs e)
{
oWebCam.OpenConnection();
}

private void btnSave_Click(object sender, EventArgs e)
{
oWebCam.SaveImage();
}

private void btnStop_Click(object sender, EventArgs e)
{
oWebCam.Dispose();
}

then the eventhandlers won't be 'wired up' to the button's Click events - in other words clicking the buttons won't cause these eventhandlers to be called.

You can test whether this is the case by putting the following statement in one of your Click handlers:

MessageBox.Show("I've been clicked!");

If nothing happens when you click the button, then it's not wired up.

If that proves to be the case, then just add the highlighted lines in the form's constructor to fix it:

public Form1()
{
InitializeComponent();
btnStart.Click += btnStart_Click;
btnSave.Click += btnSave_Click;
btnStop.Click += btnStop_Click;
}

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