Best way for custom theme

Hi, so I want to be able to have interchangeable themes within my application and I thought of two ways I could do this:

Xaml Files
By this the user would be able to select an XAML file containing the brushes for the controls I want to style, so like this:

Code:

---

<ResourceDictionary
  xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
  xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml">

        <!-- Normal -->
    <LinearGradientBrush x:Key="NormalBackground" StartPoint="0,0" EndPoint="0,1">
        <GradientBrush.GradientStops>
            <GradientStopCollection>
                <GradientStop Color="#f1f5f6" Offset="0.0"/>
                <GradientStop Color="#c9d7da" Offset="1.0"/>
            </GradientStopCollection>
        </GradientBrush.GradientStops>
    </LinearGradientBrush>
    <SolidColorBrush x:Key="NormalBorder" Color="#1785f8" />
        <SolidColorBrush x:Key="Foreground" Color="#637275" />
    <Thickness x:Key="NormalThickness" Left="3" Top="3" Right="3" Bottom="3" />
       
</ResourceDictionary>

---

Are there any disadvantages to letting users doing this, such as them being able to add XAML on themselves like:

Code:

---

<Style x:Key="LeftScrollViewer" TargetType="{x:Type ScrollViewer}">
<!-- Rest of stuff here -->

---

Which would be a problem because I only intend certain parts of the application to be skinable, the XAML file would contain the brushes and then I would do the styling.

or

XML Files
So this was I was thinking that, like XAML files the users would be able to select one that would contain the theme data:

Code:

---

<?xml version="1.0" encoding="UTF-8"?>
<Theme>
  <Normal Border="#1785f8" Thickness="0" Opacity="0.7" Foreground="#637275" Start="#f1f5f6" End="#c9d7da" />
</Theme>

---

Obviously this way isn't as flexible as merging XAML files, although it would stop users adding their own XAML to the application to edit stuff I don't want to be edited.

Any help on what way is better is appreciated, thankyou.

not sure if this is the best way, but it looks like this person thinks using 2 separate files is the best. I can't confirm or deny that is the best way, but thats probably the way that i will do it.

http://www.codeproject.com/KB/WPF/Sk...nWPFBlend.aspx