System.MethodAccessException when initializing FileStream Windows Phone 7

I'm making a WP7 that takes an image from either the gallery or the camera and by pressing a button sends it to a webservice by encoding it to a base64 string. I'm currently using the WP7 Emulator included in VS2010.

To do this, I try to use a FileStream object that will open the image stored in the image path. However, when I try to initialize the FileStream, I get in the console the message:

A first chance exception of type 'System.MethodAccessException' occurred in LiveAndesApp.dll

'taskhost.exe' (Managed): Loaded 'System.ServiceModel.Web.dll'

A first chance exception of type 'System.Xml.XmlException' occurred in System.Xml.dll

Followed by lots and lots of the System.Xml.XmlException. The weird thing is that I put the FileStream creation in a try-catch statement that catches System.MethodAccessException and E, and the program doesn't even enter it, it just goes on with the sendSighting

What am I doing wrong and how can I improve this? Thanks a lot!

Here is the complete code. This is how I call the method for converting the picture.

public void next_Click(object sender, EventArgs e)
        {
            //Dependera de si seguimos flujos offline y online. 
            if (!offline_mode)
            {
                NavigationService.Navigate(new Uri("/Pages/SendInformation.xaml?mode=online", UriKind.Relative));
                Controller c = new Controller();
                c.sendSighting();
            }
            else { NavigationService.Navigate(new Uri("/Pages/SendInformation.xaml?mode=offline", UriKind.Relative)); }

This is the code for the Controller class. I omitted everything related to the web request for the sake of brevity:

    public class Controller
    {
        public Controller()
        { }
    
        /// <summary>
        /// Manda un avistamiento al servicio.
        /// </summary>
        public void sendSighting()
        {
            //Obtenemos el a开发者_运维知识库vistamiento
            AddSightingFlowObject flow_object = AddSightingFlowObject.getInstance();
    
            //Creamos el objeto json y lo incorporamos al body del request.
            JObject json = new JObject();
    
            //Si la imagen no es nula, tenemos que procesarla.
            JArray arr = new JArray(new List<String>());
            if (flow_object.ImageControl != null)
            {
                String image_base_64 = ConvertImageToBase64(flow_object.ImagePath);
                arr.Add(image_base_64);
            }
            else
            {
                arr.Add("");
            }
            json.Add("PhotoURL", arr);
        }
    
    
        public String ConvertImageToBase64(String imagePath)
        {
            String image_base_64 = "";
            FileStream fs;
            Byte[] arr;
    
            try
            {
                fs = new FileStream(imagePath, FileMode.Open);
                arr = new Byte[fs.Length];
                fs.Read(arr, 0, arr.Length);
                image_base_64 = System.Convert.ToBase64String(arr);
            }
            catch (System.MethodAccessException e)
            {
                String error = "Error: " + e.Message + "Stack Trace: " + e.StackTrace;
            }
    
            return image_base_64;
        }

}

Thank you for your time! :D

Use Isolated Storage instead of System.IO

FileStream is part of System.IO namespace which can be replaced with smth like IsolatedStorageFileStream

Link with help