Azure Functions 3.0: What’s New for .NET Developers

Azure Functions 3.0 is now generally available, bringing .NET Core 3.1 support and significant improvements. Here’s what developers need to know.

Key Improvements

• .NET Core 3.1 Support: Run your functions on the LTS version
• Dependency Injection: First-class DI in the functions runtime
• Improved Cold Start: Faster startup times in consumption plan
• HTTP Triggered Functions: ASP.NET Core integration model

Dependency Injection Example

// Startup.cs
public class Startup : FunctionsStartup
{
    public override void Configure(IFunctionsHostBuilder builder)
    {
        builder.Services.AddScoped<IMyService, MyService>();
        builder.Services.AddHttpClient();
    }
}

// Function with DI
public class MyFunction
{
    private readonly IMyService _service;
    
    public MyFunction(IMyService service) => _service = service;

    [FunctionName("ProcessData")]
    public async Task<IActionResult> Run(
        [HttpTrigger(AuthorizationLevel.Function, "get")] HttpRequest req)
    {
        var result = await _service.ProcessAsync();
        return new OkObjectResult(result);
    }
}

Migration from 2.x

The migration is straightforward:

1. Update to .NET Core 3.1
2. Change target framework to netcoreapp3.1
3. Update NuGet packages to 3.x versions
4. Review breaking changes in Newtonsoft.Json handling

References

• Azure Functions Runtime Versions