Troubleshooting Common Issues in Microsoft Expression Blend
Microsoft Expression Blend helps designers and developers build rich XAML-based interfaces for WPF and Silverlight. Below are the most common issues you’ll encounter, why they happen, and step-by-step fixes to get you back on track.
1. Blend won’t start or crashes on launch
Possible causes: corrupted settings, incompatible add-ins, or mismatched .NET frameworks.
Steps to fix:
- Reset user settings: Run Blend with the /resetsettings switch:
- Delete cache and preferences: Close Blend and remove folders:
%LocalAppData%\Microsoft\Expression\Blend</code>
%AppData%\Microsoft\Expression\Blend</code>
- Check .NET version: Ensure required .NET frameworks are installed (usually .NET 4.x for older Blend versions).
- Disable add-ins: Remove third-party add-ins from the Blend add-ins folder and restart.
- Reinstall Blend: If problems persist, uninstall and reinstall Expression Blend.
2. XAML designer shows blank or incorrect rendering
Possible causes: runtime exceptions in user controls, design-time data issues, or incompatible custom controls.
Steps to fix:
- Open Output window: Look for design-time exceptions or binding errors reported by the designer.
- Guard runtime-only code: Wrap code that should not run in design mode:
if (!System.ComponentModel.DesignerProperties.GetIsInDesignMode(this))
{
// runtime-only initialization
}
- Use design-time data: Provide design-time view models or d:DataContext to avoid nulls:
- Isolate problematic control: Comment out custom controls or user controls to find the culprit.
- Update assembly references: Ensure control libraries target compatible .NET versions and are accessible.
3. Resources or styles not applied at runtime
Possible causes: incorrect resource dictionary merging, wrong build action, or resource key conflicts.
Steps to fix:
- Verify resource keys and locations: Ensure the resource exists in the expected dictionary.
- Merge dictionaries correctly: In App.xaml:
<Application.Resources>
<ResourceDictionary>
<ResourceDictionary.MergedDictionaries>
<ResourceDictionary Source=“Resources/Styles.xaml” />
</ResourceDictionary.MergedDictionaries>
</ResourceDictionary>
</Application.Resources>
- Check Build Action: Ensure XAML resource files are marked as “Page” (not Content).
- Avoid key collisions: Use unique keys or scopes (e.g., local vs. application-level).
- Use explicit references: If implicit styles aren’t applied, try setting Style=“{StaticResource MyStyle}” directly to confirm availability.
4. Data binding not working
Possible causes: incorrect DataContext, missing INotifyPropertyChanged implementation, or silent binding failures.
Steps to fix:
- Check DataContext hierarchy: Confirm DataContext is set where bindings expect it.
- Enable binding trace: In Output window, inspect binding error messages for missing paths or type mismatches.
- Implement INotifyPropertyChanged: Ensure view models notify property changes:
public event PropertyChangedEventHandler PropertyChanged;
protected void OnPropertyChanged(string name) =>
PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(name));
- Use correct binding syntax: Verify Binding Path and Source/RelativeSource usage.
- Test with design-time data: Temporarily set d:DataContext to validate bindings visually.
5. Assets (images/fonts) not found at runtime
Possible causes: incorrect resource paths, Copy to Output Directory settings, or assembly resource misplacement.
Steps to fix:
- Use pack URI for resources: For application resources:
- Set Build Action: For resource images use “Resource”; for content files use “Content” with “Copy if newer”.
- Check relative paths: Confirm paths are correct relative to the consuming XAML file.
- Embed fonts correctly: Add fonts to project, set Build Action to Resource, and reference in FontFamily:
FontFamily=“/AssemblyName;component/Fonts/#My Font”
6. Blend performance is slow
Possible causes: large projects, heavy design-time data, or expensive control rendering.
Steps to fix:
- Disable design-time data: Remove d:DataContext that loads large datasets.
- Turn off live visual tree updates: Close panels like Asset Library when not needed.
- Simplify templates in designer: Use lighter representations for complex controls at design time.
- Increase system resources: Close other apps, add RAM, or use SSD for faster file access.
7. Build or reference errors after upgrading project
Possible causes: target framework change, mismatched NuGet packages, or renamed assemblies.
Steps to fix:
- Retarget projects: Ensure all projects use the same .NET framework version.
- Update NuGet packages: Restore and update packages to compatible versions.
- Fix assembly references: Remove broken references and add correct project or DLL references.
- Clean and rebuild: Delete bin/obj folders and rebuild solution.
Quick checklist (copy-paste)
- Reset Blend settings and delete caches
- Inspect Output window for design-time errors
- Wrap runtime-only code with design-mode checks
- Verify resource Build Action and pack URIs
- Ensure DataContext and INotifyPropertyChanged are correct
- Use design-time data cautiously
- Clean/rebuild and retarget frameworks
If you want, I can produce a short troubleshooting script or check specific errors you’re seeing—tell me the exact error text.