To start, let’s have a look at various considerations before you consider migrating your applications to Azure App Service
Port Bindings – Azure App Service support port 80 for http and port 443 for HTTPS traffic. If you have sites using any other port after migration to Azure App Service, do remember that these are the only ports that will be used.
Usage of assemblies in the GAC (Global Assembly Cache)- This is not supported. Consider bin placing the assemblies in the local bin.
IIS5 Compatibility Mode- IIS5 Compatibility Mode is not supported. In Azure App Service each Web App and all the applications under it run in the same worker process with a specific set of application pool settings.
IIS7+ Schema Compliance- One or more elements and/or attributes are being used which are not defined in Azure App Service IIS schema. Consider using XDT transforms.
Single Application Pool Per Site- In Azure App Service each Web App and all the applications under it, run in the same application pool. In case you have applications with different application pool in IIS, consider establishing a single application pool with common settings or creating a separate Web App for each application.
COM and COM+ components- Azure App Service does not allow the registration of COM components on the platform. If your site(s) or application(s) make use of any COM components, these would need to be rewritten in managed code and deployed with the site or application.
ISAPI Extensions- Azure App Service can support the use of ISAPI Extensions, however, the DLL(s) need to be deployed with your site and registered via the web.config.
Once the above limitations have been taken into consideration, you will need to migrate your applications. The easiest form of migrating is through Azure App Service Migration Assistant. The Azure App Service Migration site and the tool can be utilized to migrate sites from Windows and Linux web servers to Azure App Service. As part of the migration the tool, this will create Web Apps and databases on Azure and publish content and publish your database.
App Settings/Connection Strings
Shared/Linked Database queries
SQL Server features