[DataServiceKey("Id")]
    public class UserData : INotifyPropertyChanged
    {
        private long _id;
        private string _surname;
        private string _name;
        private byte[] _image;

        public event PropertyChangedEventHandler PropertyChanged;

        private void NotifyPropertyChanged(string info)
        {
            if (PropertyChanged != null)
            {
                PropertyChanged(this, new PropertyChangedEventArgs(info));
            }
        }

        public long Id
        {
            get
            {
                return this._id;
            }
            set
            {
                this._id = value;
                NotifyPropertyChanged("Id");
            }
        }

        public string Surname
        {
            get
            {
                return this._surname;
            }
            set
            {
                this._surname = value;
                NotifyPropertyChanged("Surname");
            }
        }

        public string Name
        {
            get
            {
                return this._name;
            }
            set
            {
                this._name = value;
                NotifyPropertyChanged("Name");
            }
        }

        public string FullName
        {
            get
            {
                return (this.Surname + " " + this.Name).Trim();
            }
        }

        public byte[] Image
        {
            get
            { 
                return this._image; 
            }
            set
            {
                this._image = value;
                NotifyPropertyChanged("Image");
            }
        }
    }

// Выдержка из метода
                    context = context == null ? new UserEntities(this.EntitiesUri) : context;
                    var query = from u in context.User
                                where u.Id == this.UserId
                                select new UserData
                                {
                                    Id = u.Id,
                                    Name = u.Name,
                                    Surname = u.Surname,
                                    Image = u.Image
                                };
// Далее идет асинхронный запрос, в результате которого происходит присвоение DataContext'у UserGrid'а полученных результатов

        private void UploadImageButton_Click(object sender, RoutedEventArgs e)
        {
// ...Некоторые действия с OpenFileDialog
            FileStream imageStream = openImageDialog.File.OpenRead();
            byte[] b = new byte[imageStream.Length];
            imageStream.Read(b, 0, Convert.ToInt32(imageStream.Length));
            dataUser[0].Image = b;
            context.BeginSaveChanges(OnChangesSaved, context);
        }

        public void OnChangesSaved(IAsyncResult result)
        {
            Dispatcher.BeginInvoke(() =>
                {
                    context = result.AsyncState as UserEntities;
                    try
                    {
                        context.EndSaveChanges(result);
                    }
                    catch (Exception ex)
                    {
                        MessageBox.Show(ex.ToString());
                    }
                }
            );
        }

config.SetEntitySetAccessRule("User", EntitySetRights.All);