Custom Themeing model for Xamarin Forms' DynamicResource

ThemeModel.cs

[DataContract]
    public class ThemeModel : INotifyPropertyChanged
    {
        private Color backgroundColor;
        private Color textColor;
        private Color buttonBackgroundColor;
        private Color buttonTextColor;
        private Color accentColor;
        private Color headerColor;

        public ThemeModel()
        {
        }

        public ThemeModel(Color backgroundColor, Color textColor, Color buttonBackgroundColor, Color buttonTextColor, Color accentColor, Color headerColor)
        {
            this.backgroundColor = backgroundColor;
            this.textColor = textColor;
            this.buttonBackgroundColor = buttonBackgroundColor;
            this.buttonTextColor = buttonTextColor;
            this.accentColor = accentColor;
            this.headerColor = headerColor;
        }

        [DataMember]
        public Color BackgroundColor
        {
            get { return backgroundColor; }
            set { backgroundColor = value; OnPropertyChanged();}
        }

        [DataMember]
        public Color TextColor
        {
            get { return textColor; }
            set { textColor = value; OnPropertyChanged();}
        }

        [DataMember]
        public Color ButtonBackgroundColor
        {
            get { return buttonBackgroundColor; }
            set { buttonBackgroundColor = value; OnPropertyChanged();}
        }

        [DataMember]
        public Color ButtonTextColor
        {
            get { return buttonTextColor; }
            set { buttonTextColor = value; OnPropertyChanged();}
        }

        [DataMember]
        public Color AccentColor
        {
            get { return accentColor; }
            set { accentColor = value; OnPropertyChanged();}
        }

        [DataMember]
        public Color HeaderColor
        {
            get { return headerColor; }
            set { headerColor = value; OnPropertyChanged();}
        }

        public bool GetCurrentTheme()
        {
            try
            {
                BackgroundColor = (Color) App.Current.Resources["ThemeBackgroundColor"];
                TextColor = (Color) App.Current.Resources["ThemeTextColor"];
                ButtonBackgroundColor = (Color) App.Current.Resources["ThemeButtonBackgroundColor"];
                ButtonTextColor = (Color) App.Current.Resources["ThemeButtonTextColor"];
                AccentColor = (Color) App.Current.Resources["ThemeAccentColor"];
                HeaderColor = (Color) App.Current.Resources["ThemeHeaderColor"];

                return true;
            }
            catch (Exception ex)
            {
                Debug.WriteLine($"ThemeModel.GetCurrentTheme Exception: {ex}");
                return false;
            }
        }

        public bool SetCurrentTheme()
        {
            try
            {
                App.Current.Resources["ThemeBackgroundColor"] = BackgroundColor;
                App.Current.Resources["ThemeTextColor"] = TextColor;
                App.Current.Resources["ThemeButtonBackgroundColor"] = ButtonBackgroundColor;
                App.Current.Resources["ThemeButtonTextColor"] = ButtonTextColor;
                App.Current.Resources["ThemeAccentColor"] = AccentColor;
                App.Current.Resources["ThemeHeaderColor"] = HeaderColor;

                return true;
            }
            catch (Exception ex)
            {
                Debug.WriteLine($"ThemeModel.SetCurrentTheme Exception: {ex}");
                return false;
            }
        }

        public bool ResetToDefaultTheme()
        {
            try
            {
                BackgroundColor = Color.White;
                TextColor = Color.Black;
                ButtonBackgroundColor = Color.Silver;
                ButtonTextColor = Color.White;
                AccentColor = Color.FromHex("#FFEF322F");
                HeaderColor = Color.FromHex("#D8D7D7");

                return true;
            }
            catch (Exception ex)
            {
                Debug.WriteLine($"ThemeModel.SetCurrentTheme Exception: {ex}");
                return false;
            }
        }

        public void Clear()
        {
            //note to self: using properties so that prop changed is fired
            BackgroundColor = new Color();
            TextColor = new Color();
            ButtonBackgroundColor = new Color();
            ButtonTextColor = new Color();
            AccentColor = new Color();
            HeaderColor = new Color();
        }

        public event PropertyChangedEventHandler PropertyChanged;

        [NotifyPropertyChangedInvocator]
        protected virtual void OnPropertyChanged([CallerMemberName] string propertyName = null)
        {
            PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(propertyName));
        }
    }

IMPORTANT : If you're going to use this directly, make sure you have the resource defined in your App.xaml file

<Color x:Key="ThemeBackgroundColor">White</Color>
      <Color x:Key="ThemeTextColor">Black</Color>
      <Color x:Key="ThemeButtonBackgroundColor">Silver</Color>
      <Color x:Key="ThemeButtonTextColor">White</Color>
      <Color x:Key="ThemeAccentColor">#FFEF322F</Color>
      <Color x:Key="ThemeHeaderColor">#D8D7D7</Color>