Application Insights for ASP.NET Core

• 02/21/2018
• 4 minutes to read
• Contributors
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Azure Application Insights provides in-depth monitoring of your web application down to the code level. You can easily monitor your web application for availability, performance, and usage. You can also quickly identify and diagnose errors in your application without waiting for a user to report them.

This article walks you through creating a sample ASP.NET Core Razor Pages application in Visual Studio, and how to start monitoring with Azure Application Insights.

Prerequisites

• NET Core 2.0.0 SDK or later.
• Visual Studio 2017 version 15.3 or later with the ASP.NET and web development workload.

Create an ASP.NET Core project in Visual Studio

1. Right-click and Launch Visual Studio 2017 as administrator.

2. Select File > New > Project (Ctrl-Shift-N).

   

3. Expand Visual C# > Select .NET Core > ASP.NET Core Web Application. Enter a Name > Solution name > Check Create new Git repository.

   

4. Select .Net Core > ASP.NET Core 2.0 Web Application > OK.

   

Add Application Insights Telemetry

1. Select Project > Add Application Insights Telemetry... (Alternatively you can right-click Connected Services > Add Connected Service.)

   

2. Select Start Free.

   

3. Select an appropriate Subscription > Resource > and whether or not to allow collection over 1 GB per Month > Register.

   

Changes Made to your project

Application Insights is very low overhead. To review the modifications made to your project by adding Application Insights telemetry:

Select View > Team Explorer (Ctrl+, Ctrl+M) > Project > Changes

• Four changes total:

  

• One new file is created:

  ConnectedService.json

  

• Three files are modified:

  appsettings.json

  

  ContosoDotNetCore.csproj

  

  Program.cs

  

Synthetic transactions with PowerShell

Launching your app, and then clicking around on links manually can be used to generate test traffic. However, it is often helpful to create a simple synthetic transaction in PowerShell.

1. Run your app by clicking IIS Express

2. Copy the url from the browser address bar. It is in the format http://localhost:{random port number}

   

3. Run the following PowerShell loop to create 100 synthetic transactions against your test app. Modify the port number after localhost: to match the url you copied in the previous step.

   for ($i = 0 ; $i -lt 100; $i++)
   {
    Invoke-WebRequest -uri http://localhost:50984/
   }
   

Open Application Insights Portal

After running the PowerShell from the previous section, launch Application Insights to view the transactions and confirm that data is being collected.

From the Visual Studio menu, select Project > Application Insights > Open Application Insights Portal

Collect Failed Requests, Live Stream, & Page View Load Time

Failed Requests

Technically Failed Requests are being collected, but none have occurred yet. To speed the process along a custom exception can be added to the existing project to simulate a real-world exception. If your app is still running in Visual Studio before proceeding Stop Debugging (Shift+F5)

1. In Solution Explorer > expand Pages > About.cshtml > open About.cshtml.cs.

   

2. Add an Exception under Message= > save the change to the file.

   throw new Exception("Test Exception");
   

   

Live Stream

To access the Live Stream functionality of Application Insights with ASP.NET Core update to the Microsoft.ApplicationInsights.AspNetCore 2.2.0 NuGet packages.

From Visual Studio, select Project > Manage NuGet Packages > Microsoft.ApplicationInsights.AspNetCore > Version 2.2.0 > Update.

Multiple confirmation prompts will occur, read and accept if you agree with the changes.

Page View Load Time

1. In Visual Studio navigate to Solution Explorer > Pages > two files will need to be modified: _Layout.cshtml, and _ViewImports.cshtml

2. In _ViewImports.cshtml, add:

   @using Microsoft.ApplicationInsights.AspNetCore
   @inject JavaScriptSnippet snippet
   

   

3. In _Layout.cshtml add the line below before the </head> tag, but prior to any other scripts.

   @Html.Raw(snippet.FullScript)
   

   

Test Failed Requests, Page View Load Time, Live Stream

Now that you have completed the previous steps you can test out and confirm that everything is working.

1. Run your app by clicking IIS Express

2. Navigate to the About page to trigger the test exception. (If you are running in Debug mode, you will need to click Continue in Visual Studio before the exception will be picked up by Application Insights.)

3. Re-run the simulated PowerShell transaction script from earlier (You may need to adjust the port number in the script.)

4. If the Applications Insights Overview is not still open, from Visual Studio menu select Project > Application Insights > Open Application Insights Portal.

   Tip

   If you aren't seeing your new traffic yet, check the Time range and click Refresh.

   

5. Select Live Stream

   

   (If your PowerShell script is still running you should see live metrics, if has stopped run the script again with Live Stream open.)

App Insights SDK Comparison

The Application Insights product group has been working hard to achieve as close to feature parity as possible between the full .NET Framework SDK and the .Net Core SDK. The 2.2.0 release of the ASP.NET Core SDK for Application Insights has largely closed the feature gap.

To understand more about the differences and tradeoffs between .NET and .NET Core.

Performance Counters in this context refers to server-side performance counters like processor, memory, and disk utilization.

Open-source SDK

Read and contribute to the code

Video

Next steps

• Explore Users Flows to understand how users navigate through your app.
• Configure Snapshot Collection to see the state of source code and variables at the moment an exception is thrown.
• Use the API to send your own events and metrics for a more detailed view of your app's performance and usage.
• Availability tests check your app constantly from around the world.