Modern web applications demand robust error handling to ensure reliability, especially when deployed at scale. Blazor, Microsoft’s C#-based UI framework, offers two hosting models—Blazor Server and Blazor WebAssembly (WASM).
While both are capable platforms, they differ significantly in how they handle errors.
This blog focuses on error handling in Blazor Server, contrasting it with WebAssembly to help development teams choose the right strategy for real-world enterprise applications.
1. Understanding Blazor Server and WebAssembly Hosting Models
Blazor Server
- Executes C# code on the server
- Maintains a real-time connection using SignalR
- Minimal client logic, heavier server responsibility
Blazor WebAssembly
- Runs the entire .NET application inside the browser
- No persistent server connection required
- Ideal for offline capabilities and low-latency interactions
Understanding the architecture is essential, as it directly influences how runtime errors are detected, logged, and resolved.
2. Common Real-World Challenges in Error Handling
Let’s take a real-world example: a task management platform built for remote teams.
- Frequent updates and assignments
- Unreliable internet for some users
- Sensitive workflows like file uploads and notifications
These scenarios highlight the importance of choosing the right error-handling approach based on your hosting model.
3. Error Handling in Blazor Server vs WebAssembly
3.1 Network Reliability & Exception Propagation
Blazor Server – SignalR Failure
csharp
CopyEdit
@code {
private async Task LoadData() {
try {
var data = await Http.GetFromJsonAsync<List<TaskItem>>(“api/tasks”);
} catch (Exception ex) {
ErrorMessage = “Server connection lost. Please retry.”;
}
}
}
Issue: If the SignalR connection drops, Blazor Server doesn’t always throw a visible error. The UI may freeze or become unresponsive.
Recommendation: Use CircuitHandler to monitor disconnections and restore the session gracefully.
Blazor WebAssembly – Network Errors
csharp
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@code {
private async Task LoadData() {
try {
var data = await Http.GetFromJsonAsync<List<TaskItem>>(“api/tasks”);
} catch (HttpRequestException ex) {
ErrorMessage = “Check your internet connection.”;
}
}
}
Advantage: In WebAssembly, exceptions like fetch failures are caught immediately. This improves error traceability for client-side issues.
3.2 Centralized Error Handling
Blazor Server: Server-Side Middleware Approach
csharp
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app.UseExceptionHandler(“/Error”);
app.Use(async (context, next) => {
try {
await next();
} catch (Exception ex) {
// Logging or alerting
}
});
This allows for centralized exception logging and handling in enterprise-grade apps.
Blazor WebAssembly: Using ErrorBoundary
razor
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<ErrorBoundary>
<ChildContent>
<TaskList />
</ChildContent>
<ErrorContent>
<p>Something went wrong. Try refreshing the page.</p>
</ErrorContent>
</ErrorBoundary>
WebAssembly does not support server-side middleware, so it relies on UI-level exception control using ErrorBoundary.
3.3 Debugging Differences
| Feature | Blazor Server | Blazor WebAssembly |
| Stack trace accuracy | High (server-side clarity) | Often minified or obfuscated |
| Live reload support | Fast (hot reload supported) | Slower due to recompilation |
| In-browser debugging | No (relies on server logs) | Yes (via browser dev tools) |
4. Performance Impact of Error Handling
| Concern | Blazor Server | Blazor WebAssembly |
| Latency in error UI | Higher (due to SignalR dependency) | Lower (local catch and render) |
| Bandwidth use | Higher (each UI update is a roundtrip) | Lower (client-side handling) |
| Memory consumption | Low on client, high on server | Higher on client browser |
5. Best Practices for Error Handling in Blazor Server
Use CircuitHandler:
Detect and respond to SignalR connection changes or session timeouts.
Implement Middleware Logging:
Use UseExceptionHandler and custom middleware for centralized exception management.
Add Retry Logic:
Design UI with retry mechanisms for key user actions.
Monitor and Alert:
Integrate server-side error tracking tools like Serilog, Application Insights, or Sentry.
6. When to Choose Blazor Server for Better Error Control
| Use Case | Recommendation | Reason |
| Enterprise-scale app with secure workflows | Blazor Server | Centralized logic and robust logging |
| Need real-time updates with reliability | Blazor Server | Server control via SignalR |
| Strict audit logging and compliance | Blazor Server | Better exception traceability |
If offline capabilities or browser-native speed is more critical, Blazor WebAssembly is worth considering—but it offers less control over global error states.
Conclusion
Effective error handling in Blazor Server is essential for delivering stable and secure enterprise applications. By leveraging server-side middleware, CircuitHandler, and logging tools, you can ensure graceful failure, better UX, and system reliability.
As enterprise applications scale, having a well-defined error management strategy gives your product an edge in performance and stability.
Additional Resources: