Xamarin ios - Error while accessing tag property from sender

Question

I'm trying to access a button via the sender object inside a handler. However, I keep getting this exception:

Specified cast is not valid.

I know it's a simple issue but could someone help me see what I'm missing? It also doesn't have to specifically be the tag, I would just like to know which button was clicked.

This is the line where I get the exception:

var tag = ((UIButton)sender).Tag;


protected void Handle_FinishedPickingMedia (object sender, UIImagePickerMediaPickedEventArgs e)
    {
        try{

            //determine what was selected, video or image
            bool isImage = false;
            switch(e.Info [UIImagePickerController.MediaType].ToString()) {
            case "public.image":
                Console.WriteLine("Image selected");
                isImage = true;
                break;
            }
// if it was an image, get the other image info
            if(isImage) {
                // get the original image
                UIImage originalImage = e.Info[UIImagePickerController.OriginalImage] as UIImage;
                if(originalImage != null) {
                    // do something with the image

                    new Thread(new System.Threading.ThreadStart(() => {
                        Thread.Sleep(350);

                        BeginInvokeOnMainThread (() => {

                            var tag = ((UIButton)sender).Tag;

                            //UIButton senderButton = (UIButton)sender;

                            switch(tag)
                            {
                            case 0:
// do something here

                                break;
                            case 1:

// do something here                                    
break;
});
                    })).Start();
                }
            } 
            // dismiss the picker
            imagePicker.DismissModalViewController (true);
}catch(Exception ex)
        {
            ShowAlert ("Failed !", "Unable to select image", "");

            Console.WriteLine(ex.Message + ex.StackTrace);

        }
    }

Answer 1

try something like this:

UIButton button = sender as UIButton;
var tag = button.tag;

also you can add some checks for the case when the "button" is null, eg. sender is not a UIButton

Answer 2

Based on Jason's suggestion above, the UIImagePickerController was the sender and not the buttons launching the picker. This is how I fixed the issue:

1. Created a global tag variable

     int tag { get; set; } 

2. Assigned the tag value inside each button's click handler. For instance:

    button.TouchUpInside += (object sender, EventArgs e) => { tag = 0; // Do other stuff here }; 

3. The use the tag variable in the switch statement.