C# accessing form member from separate class

Question

Hi all,

I need some advice please on the best way to achieve a particular outcome...

My scenario...

I have a Form1 class, which is my main Form with a picture box on it.

I have a second class called camera that using an event handler grabs a frame (bitmap) from my webcam.

I then want to pass this frame to the picture box in the main form in the best fashion.

At the moment in the main form I have the code:

public static void setPB(Bitmap image) 
{

var form = Form.ActiveForm as Form1;
form.pbWebCamDisplay = image;

}

then in the Camera class I use

Form1.setPB(currentFrame);

This works fine, however I wasn't sure if this was best programming practice? Is it possible to use custom events?

Thanks in advance for any help

Tom

Answer 1

I would use events if I were in your place.

Answer 2

Yeah, I would say is perfectly good. You have a camera class that is in charge of handling the camera input and a public setter for a private member of your form. I would not change a bit.

That way you separate the different responsibilities for the functionalities into different classes. Don't handle the camera events inside the Form class, instead do as you're doing.

Answer 3

I would create a method on the Camera class, which takes the picture and returns a Bitmap object.

So in the OnLoad or in the OnClick of a button, call that method and set the return value to the PictureBox...

var picture = new Camera().TakePicture();
myPictureBox.Image = picture;

Something like that :)

Edit: If the Camera class is an Event driven component (Camera.NewFrame event), try:

(in the constructor):

var camera = new Camera();
camera.OnNewFrame += new OnNewFrameEventHandler(MyEventHandler);

(event handler)

public void MyEnventHandler(EventArgs comingFromComponent)
{
   var image = comingFromComponent.Frame; // (hopefully this is the case :))
   myPictureBox.Image = image;
}

Answer 4

Definitely, events are the right choice. You can implement Observer Design Pattern using them. Your current implementation is not best practice - it forces tight coupling between Camera and Form class.

Answer 5

what drives the event that make Camera class grab the picture? This is important.

You don't even need the PictureBox setter in the form if the event is fired by the form itself.

BTW, i'm with Jorge Córdoba, a setter and a grab event are all that you need. Occam razor.

Answer 6

You can use Composition here i.e. ask yourself that Can my camera live outside of my form?

if you got answer as NO

than

Create a Property in Form class

public Camera myCamera {get;set;}

assign this property in your form constructor

public Form()

{ myCamera = new Camera (); }

and then use myCamera perperty.

another way , you can say that you are injecting your Dependency using Constructor Injection which is more advance topic of 'Dependency Injection'