C# WebCam with .dll wrapper

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• 

  Vulpes14y agoPosted Apr 19, 2012, 6:57 PM

  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.
• JL

  John Luciani14y agoPosted Apr 19, 2012, 7:01 PM

  Fantastic!!! Thanks for all the help!
• JL

  John Luciani14y agoPosted Apr 19, 2012, 4:50 PM

  The did work! Thanks!! Now I get an error of: NullReference Exception was unhandled at the line for oWebCam.OpenConnection();
• 

  Vulpes14y agoPosted Apr 19, 2012, 4:16 PM

  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;

          }