I have started to migrate some of my .NET Core 3.1 applications to .NET 5. But to be able to run these in Azure App Service an extension needs to be installed.

The problem

If you have an Azure App Service, it is not hard to enable .NET 5 in that service. In the Azure portal, open the service, select Extensions, and then select the appropriate version.

This is quite straightforward. But if you have several services, or several deployment slots (each slot require its own extension), this will be a tedious task.

The solution

This is how you install an extension to an App Service in PowerShell:

PowerShell 
New-AzureRmResource -ResourceType "Microsoft.Web/sites/siteextensions" `
    -ResourceGroupName MyResourceGroup `
    -Name "MyApService/AspNetCoreRuntime.5.0.x64" `
    -ApiVersion "2018-02-01" `
    -Force

If you want to install it to a deployment slot, this is the way:

PowerShell 
New-AzureRmResource -ResourceType "Microsoft.Web/sites/slots/siteextensions" `
    -ResourceGroupName MyResourceGroup `
    -Name "MyApService/Staging/AspNetCoreRuntime.5.0.x64" `
    -ApiVersion "2018-02-01" `
    -Force

Summary

I often prefer making changes via a UI, but in scenarios like this the command line is the way to go. It was tricky to figure out how to do this. It was also tricky to find out the proper name for the extension. I find the name by first manually install the extension, and then generate an ARM-template for the resource group.