Hey there! Let's work through this together. I notice you've started defining custom primary colors in your App.xaml for your MaterialDesign-in-XAML WPF app, but your code snippet got cut off. Based on what you shared and common issues with this setup, here's how to fix and properly structure your resource dictionary to get those custom colors working.

First, let's format the partial code you provided correctly:

<Application.Resources>
    <ResourceDictionary>
        <!-- primary -->
        <SolidColorBrush x:Key="PrimaryHueLightBrush" Color="#033059"/><!--5c5b5e-->
        <SolidColorBrush x:Key="PrimaryHueLightForegroundBrush" Color="#FFFFFF"/>
        <!-- I assume the rest of your primary/secondary color brushes were cut off here -->
    </ResourceDictionary>
</Application.Resources>

Now, here are the key fixes and best practices to ensure your custom colors apply:

• Merge MaterialDesign resources first, then add your overrides
  Your custom brushes need to come after the base MaterialDesign resource dictionaries so they override the default theme colors. This is the most common mistake! Your App.xaml should look like this:

  <Application.Resources>
      <ResourceDictionary>
          <ResourceDictionary.MergedDictionaries>
              <!-- Load MaterialDesign's base theme and defaults first -->
              <materialDesign:BundledTheme BaseTheme="Light" PrimaryColor="Blue" SecondaryColor="LightBlue"/>
              <ResourceDictionary Source="pack://application:,,,/MaterialDesignThemes.Wpf;component/Themes/MaterialDesignTheme.Defaults.xaml" />
          </ResourceDictionary.MergedDictionaries>
          
          <!-- Your custom color overrides go here -->
          <SolidColorBrush x:Key="PrimaryHueLightBrush" Color="#033059"/>
          <SolidColorBrush x:Key="PrimaryHueLightForegroundBrush" Color="#FFFFFF"/>
          <!-- Don't forget all required primary hue brushes—missing these will cause some controls to use defaults -->
          <SolidColorBrush x:Key="PrimaryHueMidBrush" Color="#022546"/>
          <SolidColorBrush x:Key="PrimaryHueMidForegroundBrush" Color="#FFFFFF"/>
          <SolidColorBrush x:Key="PrimaryHueDarkBrush" Color="#011A33"/>
          <SolidColorBrush x:Key="PrimaryHueDarkForegroundBrush" Color="#FFFFFF"/>
      </ResourceDictionary>
  </Application.Resources>
  

• Ensure you override all necessary brush keys
  MaterialDesign uses a set of specific brush keys for each hue (light, mid, dark) and their corresponding foregrounds. If you skip any, controls that rely on those missing brushes will fall back to the default theme colors. Double-check that you've covered all primary (and secondary, if needed) hue brushes.

• Check for resource dictionary ordering issues
  If you have multiple custom resource dictionaries, make sure they're merged in the right order: MaterialDesign base resources first, then your custom overrides. Any duplicate keys later in the list will override earlier ones.

• Trigger a theme refresh if colors don't apply on startup
  If your custom colors still aren't showing up, you can force a theme refresh in your app's startup code (e.g., in App.xaml.cs):

  protected override void OnStartup(StartupEventArgs e)
  {
      base.OnStartup(e);
      
      // Refresh the theme to apply custom colors
      var mainWindow = new MainWindow();
      MaterialDesignThemes.Wpf.ThemeExtensions.SetPrimaryColor(mainWindow, (Color)ColorConverter.ConvertFromString("#033059"));
      mainWindow.Show();
  }
  

内容的提问来源于stack exchange，提问作者georgehatzi