Monitoring and Telemetry

Integrate Application Insights to track client-side errors and performance metrics.

In this lesson, you will learn how to integrate Application Insights into a Blazor WebAssembly application to capture client-side errors and performance metrics.

While your backend telemetry is essential, your Blazor WebAssembly app runs entirely in the user's browser, making it a "black box" unless you explicitly instrument it. By using the Microsoft.ApplicationInsights JavaScript SDK bridged through your Blazor project, you can track how your UI performs in the wild.

Configuring the Telemetry Bridge

To start, you add the Application Insights SDK to your wwwroot/index.html. This script initializes the telemetry client so it can begin reporting data to your Azure resource.

<script type="text/javascript">
    var appInsights = new ApplicationInsights({ config: {
        instrumentationKey: 'YOUR_INSTRUMENTATION_KEY'
    }});
    appInsights.loadAppInsights();
    appInsights.trackPageView();
</script>

Tracking Exceptions and Custom Metrics

Once initialized, you need to capture client-side logic failures. Because Blazor runs in C#, you use JS Interop to pass error data from your ErrorBoundary components or global exception handlers directly to the browser’s telemetry object.

In your App.razor or a global error handler, you can catch unhandled exceptions:

public async Task HandleError(Exception ex)
{
    // Pass the exception details to the JS Application Insights instance
    await JS.InvokeVoidAsync("appInsights.trackException", new { 
        exception = ex.Message, 
        severityLevel = 3 // Error
    });
}

Measuring Performance

Telemetry isn’t just for crashes; it’s for understanding user friction. You can use the trackMetric method to record how long specific "Long-running Tasks" take to complete. By wrapping your logic in a timer and sending the duration to Application Insights, you can create custom dashboards in the Azure Portal to visualize exactly when your application slows down for the end user.

This approach provides the same observability level for your frontend as you already have for your backend services, allowing you to correlate a user's slow page load with specific API latency or client-side bottlenecks.

Key Takeaway: Integrating Application Insights into Blazor allows you to bridge the visibility gap by piping client-side exceptions and performance metrics directly into your existing Azure monitoring dashboard.