Instrumentation Key is the key integration point between your application and the Application Insights. This key is essential for sending the application telemetry data back to azure. If you create the Application Insights directly using Visual Studio; Visual Studio takes care of linking between your application and the key. If you create the Application Insights in portal first and then want to integrate with your apps, then you may need to do this link manually.
If you want to do a manual integration; you have to obtain the Application Insights Instrumentation Key and In the past I have showed how to get the instrumentation key from the portal . Below screenshot shows the quick reference of it.
Now, here is the interesting part, you can view the instrumentation key directly from the Visual Studio by using the Cloud Explorer Extension. If you are working with Azure, this tool must be very much familiar with you. You can launch it from View –> Cloud Explorer.
Once Launch, it would required for your first time authentication with your azure account.
Once the authentication is successfully along with your other azure resources such as Storage Accounts, Stream Jobs, Virtual Machine etc. you will get list of all of your Application Insights.
Select the respective Application Insights from the list, and you can now jump into Portal or Search Windows ( Well this is a new addition for find the search … with my previous blog post .. here Different ways to launch the Application Insights Search Window in Visual Studio ) .
Move to Properties Tab, and there you will have Instrumentation key along with other common properties.
You can take advantage of this utility to easily get common properties for a specific Application Insights.