How to convert color code into media.brush?

I have a rectangle that i want to fill with a color. When i write Fill = "#FFFFFF90" it shows me an error:

> Cannot implicitly convert type 'string' to 'System.Windows.Media.Brush

Please give me some advice.

You could use the same mechanism the XAML reading system uses: Type converters

var converter = new System.Windows.Media.BrushConverter();
var brush = (Brush)converter.ConvertFromString("#FFFFFF90");
Fill = brush;

In code, you need to explicitly create a Brush instance:

Fill = new SolidColorBrush(Color.FromArgb(0xff, 0xff, 0x90))

For WinRT (Windows Store App)

using Windows.UI;
using Windows.UI.Xaml.Media;
   
    public static Brush ColorToBrush(string color) // color = "#E7E44D"
    {
        color = color.Replace("#", "");
        if (color.Length == 6)
        {
            return new SolidColorBrush(ColorHelper.FromArgb(255,
                byte.Parse(color.Substring(0, 2), System.Globalization.NumberStyles.HexNumber),
                byte.Parse(color.Substring(2, 2), System.Globalization.NumberStyles.HexNumber),
                byte.Parse(color.Substring(4, 2), System.Globalization.NumberStyles.HexNumber)));
        }
        else
        {
            return null;
        }
    }

Sorry to be so late to the party! I came across a similar issue, in WinRT. I'm not sure whether you're using WPF or WinRT, but they do differ in some ways (some better than others). Hopefully this will help people across the board, whichever situation they're in.

You could always use the code from the converter class I created to re-use and do in your C# code-behind, or wherever you're using it, to be honest:

I made it with the intention that a 6-digit (RGB), or an 8-digit (ARGB) Hex value could be used either way.

So I created a converter class:

public class StringToSolidColorBrushConverter : IValueConverter
{
    public object Convert(object value, Type targetType, object parameter, string language)
    {
        var hexString = (value as string).Replace("#", "");

        if (string.IsNullOrWhiteSpace(hexString)) throw new FormatException();
        if (hexString.Length != 6 || hexString.Length != 8) throw new FormatException();

        try
        {
            var a = hexString.Length == 8 ? hexString.Substring(0, 2) : "255";
            var r = hexString.Length == 8 ? hexString.Substring(2, 2) : hexString.Substring(0, 2);
            var g = hexString.Length == 8 ? hexString.Substring(4, 2) : hexString.Substring(2, 2);
            var b = hexString.Length == 8 ? hexString.Substring(6, 2) : hexString.Substring(4, 2);

            return new SolidColorBrush(ColorHelper.FromArgb(
                byte.Parse(a, System.Globalization.NumberStyles.HexNumber),
                byte.Parse(r, System.Globalization.NumberStyles.HexNumber),
                byte.Parse(g, System.Globalization.NumberStyles.HexNumber),
                byte.Parse(b, System.Globalization.NumberStyles.HexNumber)));
        }
        catch
        {
            throw new FormatException();
        }
    }

    public object ConvertBack(object value, Type targetType, object parameter, string language)
    {
        throw new NotImplementedException();
    }
}

Added it into my App.xaml:

<ResourceDictionary>
    ...
    <converters:StringToSolidColorBrushConverter x:Key="StringToSolidColorBrushConverter" />
    ...
</ResourceDictionary>

And used it in my View's Xaml:

<Grid>
    <Rectangle Fill="{Binding RectangleColour,
               Converter={StaticResource StringToSolidColorBrushConverter}}"
               Height="20" Width="20" />
</Grid>

Works a charm!

Side note... Unfortunately, WinRT hasn't got the System.Windows.Media.BrushConverter that H.B. suggested; so I needed another way, otherwise I would have made a VM property that returned a SolidColorBrush (or similar) from the RectangleColour string property.

For simplicity you could create an extension:-

    public static SolidColorBrush ToSolidColorBrush(this string hex_code)
    {
        return (SolidColorBrush)new BrushConverter().ConvertFromString(hex_code);
    }

And then to use:-

 SolidColorBrush accentBlue = "#3CACDC".ToSolidColorBrush();

What version of WPF are you using? I tried in both 3.5 and 4.0, and Fill="#FF000000" should work fine in a in the XAML. There is another syntax, however, if it doesn't. Here's a 3.5 XAML that I tested with two different ways. Better yet would be to use a resource.

<Window x:Class="WpfApplication2.MainWindow"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    Title="MainWindow" Height="350" Width="525">
<Grid>
    <Rectangle Height="100" HorizontalAlignment="Left" Margin="100,12,0,0" Name="rectangle1" Stroke="Black" VerticalAlignment="Top" Width="200" Fill="#FF00AE00" />
    <Rectangle Height="100" HorizontalAlignment="Left" Margin="100,132,0,0" Name="rectangle2" Stroke="Black" VerticalAlignment="Top" Width="200" >
        <Rectangle.Fill>
            <SolidColorBrush Color="#FF00AE00" />
        </Rectangle.Fill>
    </Rectangle>
</Grid>