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Find and diagnose runtime exceptions with Application Insights

Application Insights collects telemetry from your application to help identify and diagnose runtime exceptions. This tutorial takes you through this process with your application. You learn how to:

  • Modify your project to enable exception tracking.
  • Identify exceptions for different components of your application.
  • View details of an exception.
  • Download a snapshot of the exception to Visual Studio for debugging.
  • Analyze details of failed requests by using query language.
  • Create a new work item to correct the faulty code.


To complete this tutorial:

  • Install Visual Studio 2019 with the following workloads:
    • ASP.NET and web development
    • Azure development
  • Download and install the Visual Studio Snapshot Debugger.
  • Enable the Visual Studio Snapshot Debugger
  • Deploy a .NET application to Azure and enable the Application Insights SDK
  • Modify your code in your development or test environment to generate an exception because the tutorial tracks the identification of an exception in your application.

Sign in to Azure

Sign in to the Azure portal.

Analyze failures

Application Insights collects any failures in your application. It lets you view their frequency across different operations to help you focus your efforts on those issues with the highest impact. You can then drill down on details of these failures to identify the root cause.

  1. Select Application Insights and then select your subscription.

  2. To open the Failures pane, either select Failures under the Investigate menu or select the Failed requests graph.

    Screenshot that shows failed requests.

  3. The Failed requests pane shows the count of failed requests and the number of users affected for each operation for the application. By sorting this information by user, you can identify those failures that most affect users. In this example, GET Employees/Create and GET Customers/Details are likely candidates to investigate because of their large number of failures and affected users. Selecting an operation shows more information about this operation in the right pane.

    Screenshot that shows the Failed requests pane.

  4. Reduce the time window to zoom in on the period where the failure rate shows a spike.

    Screenshot that shows the Failed requests window.

  5. See the related samples by selecting the button with the number of filtered results. The Suggested samples have related telemetry from all components, even if sampling might have been in effect in any of them. Select a search result to see the details of the failure.

    Screenshot that shows the Failed request samples.

  6. The details of the failed request show the Gantt chart that shows that there were two dependency failures in this transaction, which also contributed to more than 50% of the total duration of the transaction. This experience presents all telemetry across components of a distributed application that are related to this operation ID. You can select any of the items to see their details on the right side.

    Screenshot that shows Failed request details.

  7. The operations detail also shows a format exception, which appears to have caused the failure. You can see that it's because of an invalid Zip Code. You can open the debug snapshot to see code-level debug information in Visual Studio.

    Screenshot that shows exception details.

Identify failing code

The Snapshot Debugger collects snapshots of the most frequent exceptions in your application to assist you in diagnosing its root cause in production. You can view debug snapshots in the portal to see the call stack and inspect variables at each call stack frame. Afterward, you can debug the source code by downloading the snapshot and opening it in Visual Studio 2019 Enterprise.

  1. In the properties of the exception, select Open debug snapshot.

  2. The Debug Snapshot pane opens with the call stack for the request. Select any method to view the values of all local variables at the time of the request. Starting from the top method in this example, you can see local variables that have no value.

    Screenshot that shows the Debug Snapshot pane.

  3. The first call that has valid values is ValidZipCode. You can see that a Zip Code was provided with letters that can't be translated into an integer. This issue appears to be the error in the code that must be corrected.

    Screenshot that shows an error in the code that must be corrected.

  4. You can then download this snapshot into Visual Studio where you can locate the actual code that must be corrected. To do so, select Download Snapshot.

  5. The snapshot is loaded into Visual Studio.

  6. You can now run a debug session in Visual Studio Enterprise that quickly identifies the line of code that caused the exception.

    Screenshot that shows an exception in the code.

Use analytics data

All data collected by Application Insights is stored in Azure Log Analytics, which provides a rich query language that you can use to analyze the data in various ways. You can use this data to analyze the requests that generated the exception you're researching.

  1. Select the CodeLens information above the code to view telemetry provided by Application Insights.

    Screenshot that shows code in CodeLens.

  2. Select Analyze impact to open Application Insights Analytics. It's populated with several queries that provide details on failed requests, such as affected users, browsers, and regions.

    Screenshot that shows Application Insights window that includes several queries.

Add a work item

If you connect Application Insights to a tracking system, such as Azure DevOps or GitHub, you can create a work item directly from Application Insights.

  1. Return to the Exception Properties pane in Application Insights.

  2. Select New Work Item.

  3. The New Work Item pane opens with details about the exception already populated. You can add more information before you save it.

    Screenshot that shows the New Work Item pane.

Next steps

Now that you've learned how to identify runtime exceptions, advance to the next tutorial to learn how to identify and diagnose performance issues.