Azure Functions and .NET 5: Query params, Dependency Injection, Bicep & Build

The upgrade of Azure Functions from .NET Core 3.1 to .NET 5 is significant. There's an excellent guide for the general steps required to perform the upgrade. However there's a number of (unrelated) items which are not covered by that post:

• Query params
• Dependency Injection
• Bicep
• Build

This post will show how to tackle these.

Query params

As part of the move to .NET 5 functions, we say goodbye to HttpRequest and hello to HttpRequestData. Now HttpRequest had a useful Query property which allowed for the simple extraction of query parameters like so.

HttpRequestData has no such property. However, it's straightforward to make our own. It's simply a matter of using System.Web.HttpUtility.ParseQueryString on req.Url.Query and using that:

Dependency Injection, local development and Azure Application Settings

Dependency Injection is a much more familiar shape in .NET 5 if you're familiar with .NET Core web apps. Once again we have a Program.cs file. To get the configuration built in such a way to support both local development and when deployed to Azure, there's a few things to do. When deployed to Azure you'll likely want to read from Azure Application Settings:

To tackle both of these, you'll want to use AddJsonFile and AddEnvironmentVariables in ConfigureAppConfiguration. A final Program.cs might look something like this:

With this approach in place, when the application runs, it should construct a configuration driven by all the providers required to run our application.

Bicep

When it comes to deploying to Azure via Bicep, there's some small tweaks required:

• appSettings.FUNCTIONS_WORKER_RUNTIME becomes dotnet-isolated
• linuxFxVersion becomes DOTNET-ISOLATED|5.0

Applied to the resource itself the diff looks like this:

Building .NET 5 functions

Before signing off, there's one more thing to slip in. When attempting to build .NET 5 Azure Functions with the .NET SDK alone, you'll encounter this error:

Docs on this seem to be pretty short. The closest I came to docs was this comment on Stack Overflow:

To build .NET 5 functions, the .NET Core 3 SDK is required. So this must be installed alongside the 5.0.x sdk.

So with Azure Pipelines you might have have something that looks like this:

Have fun building .NET 5 functions!