WPF Application how to convert grid background xaml to c#?

Question

I have a wpf app that I would like to allow the user to switch the 'Theme', which is simply the grid background.

This is the XAML:

<Grid x:Name="rabGrid">
    <Grid.Background>
        <LinearGradientBrush EndPoint="0.5,1" StartPoint="0.5,0">
            <GradientStop Color="#FF080D39"/>
            <GradientStop Color="White"/>
            <GradientStop Color="#FF838589" Offset="1"/>
            <GradientStop Color="#FF2E4999" Offset="0.997"/>
        </LinearGradientBrush>
    </Grid.Background>

Here's what I have in c#:

    private void rTheme_Click(object sender, RoutedEventArgs e)
    {

        LinearGradientBrush rabThem = new LinearGradientBrush();
        rabThem.StartPoint = new Point(0.5, 0);
        rabThem.EndPoint = new Point(0.5, 1);

        GradientStop rabThemStop = new GradientStop();
        rabThemStop.Color = Color.FromArgb(100, 8, 13, 57);

        GradientStop rabThemStop1 = new GradientStop();
        rabThemStop1.Color = Colors.White;

        GradientStop rabThemStop2 = new GradientStop();
        rabThemStop2.Color = Color.FromArgb(100, 131, 133, 137);
        rabThemStop2.Offset = 1;

        GradientStop rabThemStop3 = new GradientStop();
        rabThemStop3.Color = Color.FromArgb(100, 46, 73, 153);
        rabThemStop3.Offset = .997;

    }

My idea behind the above code is to setup all the metrics, then somehow fill to the background.

I have also tried variations like this with no joy:

        clasGrid.Background = new LinearGradientBrush();
        clasGrid.StartPoint = new Point(0.5, 0);
        clasGrid.EndPoint = new Point(0.5, 1);

I'm can change the background with something like this:

clasGrid.Background = new LinearGradientBrush(Colors.LightBlue, Colors.SlateBlue, 90);

Implementing some of the syntax from the answer below, I've came up with this:

        LinearGradientBrush rabThem = new LinearGradientBrush();
        rabThem.EndPoint = new Point(0.5, 1);
        rabThem.StartPoint = new Point(0.5, 0);

        GradientStop rabThemStop = new GradientStop();
        rabThemStop.Color = Color.FromArgb(100, 8, 13, 57);

        GradientStop rabThemStop1 = new GradientStop();
        rabThemStop1.Color = Colors.White;

        GradientStop rabThemStop2 = new GradientStop();
        rabThemStop2.Color = Color.FromArgb(100, 131, 133, 137);
        rabThemStop2.Offset = 1;

        GradientStop rabThemStop3 = new GradientStop();
        rabThemStop3.Color = Color.FromArgb(100, 46, 73, 153);
        rabThemStop3.Offset = .997;


        rabThem.GradientStops.Add(rabThemStop);
        rabThem.GradientStops.Add(rabThemStop1);
        rabThem.GradientStops.Add(rabThemStop2);
        rabThem.GradientStops.Add(rabThemStop3);


        clasGrid.Background = rabThem;

While this works, the colors are a lot lighter (as if the gradient is not correct) and am still trying to figure that part out.

Answer 1

You have to set up the gradient each time. You can either make a method for it, or you can make a converter. I'm using a boolean to control which background is used, but you can use whatever value you want. If you choose to make a method, you can base it off of my converter.

   public class OptionOrderBackgroundConverter : IValueConverter
   {
      public object Convert(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture)
      {
         // Create a background and return
         bool b = (value != null ? (bool)value : false);
         if (!b)
         {
            LinearGradientBrush lb = new LinearGradientBrush();
            lb.StartPoint = new System.Windows.Point(0, 0);
            lb.EndPoint = new System.Windows.Point(0, 1);
            GradientStop gstop = new GradientStop(ViewModels.QuoteButtonStyle.Instance.QuoteButtonTopBackgroundColor, 0);
            lb.GradientStops.Add(gstop);
            gstop = new GradientStop(ViewModels.QuoteButtonStyle.Instance.QuoteButtonBottomBackgroundColor, 0.9);
            lb.GradientStops.Add(gstop);
            return lb;
         }
         else
         {
            LinearGradientBrush lb = new LinearGradientBrush();
            lb.StartPoint = new System.Windows.Point(0, 0);
            lb.EndPoint = new System.Windows.Point(0, 1);
            GradientStop gstop = new GradientStop(Colors.Orange, 0);
            lb.GradientStops.Add(gstop);
            gstop = new GradientStop(Colors.WhiteSmoke, 0.9);
            lb.GradientStops.Add(gstop);
            return lb;
         }
      }

      public object ConvertBack(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture)
      {
         throw new NotImplementedException();
      }
   }

For the converter, I bind it to the control like this:

Background="{Binding Path=IsDealable, FallbackValue=False, Converter={StaticResource OptionOrderBackgroundConverter}}"

If you use a converter and want to be able to pass in 2 colors, you can change it to an IMultiValueConverter .