依赖注入不适用于 Azure Functions

Question

I have a problem with dependecy injection in Azure Functions. I read every guide and any issue here on stackoverflow but I can't found a solution.

I'm working with Visual Studio 2019 and Azurite for testing in my local machine. I tried to make a project without and It works fine. The project is an Azure Functions with HttpTrigger.

Here the link to my github repository

I paste here my Startup's code:

[assembly: FunctionsStartup(typeof(Startup))]

namespace ZanettiClod.SampleAzureFunctions
{
    public class Startup : FunctionsStartup
    {
        public override void Configure(IFunctionsHostBuilder builder)
        {
            builder.Services.AddHttpClient();
            builder.Services.AddSingleton<IProductService, ProductService>();
            builder.Services.AddSingleton<IProductRepository<Product>, ProductRepository>();
        }
    }
} 

And my Program's code:

namespace ZanettiClod.SampleAzureFunctions
{
    public class Program
    {
        public static void Main()
        {

            var host = new HostBuilder()
                .ConfigureFunctionsWorkerDefaults()
                .Build();
            host.Run();
        }
    }
}

My GetProducts's Code:

namespace ZanettiClod.SampleAzureFunctions
{
    public class GetProducts
    {
        private readonly IProductService _productService;

        public GetProducts(IProductService productService)
        {
            _productService = productService;
        }

        [Function("GetProducts")]
        public async Task<HttpResponseData> Run(
            [HttpTrigger(AuthorizationLevel.Anonymous, "get")] 
            HttpRequestData req,
            FunctionContext executionContext)
        {
            var logger = executionContext.GetLogger("GetProducts");
            logger.LogInformation("C# HTTP trigger function processed a request.");

            var products = await _productService.GetAllProducts();

            var response = req.CreateResponse(HttpStatusCode.OK);
            await response.WriteAsJsonAsync(products);

            return response;
        }
    }
}

And here is the error I get back: screeshot

Thanks in advance for the help

Answer 1

You could make below changes to make it work. I tested for Dependency injection and it worked.

1. Move dependency injection from startup.cs to program.cs. That's how it works for target framework .Net 5.0. Documentation - https://docs.microsoft.com/en-us/azure/azure-functions/dotnet-isolated-process-guide

    namespace ZanettiClod.SampleAzureFunctions { public class Program { public static void Main() { var host = new HostBuilder() .ConfigureFunctionsWorkerDefaults() .ConfigureServices(s => { s.AddHttpClient(); s.AddSingleton<IProductService, ProductService>(); s.AddSingleton<IProductRepository<Product>, ProductRepository>(); }) .Build(); host.Run(); } } }

2. Change the qualifier for _productService from static to readonly in CreateProduct class. Dependency injection doesn't work on static member variables. Also remove static qualifier from your function.

    public class CreateProduct { private readonly IProductService _productService; public CreateProduct(IProductService productService) { _productService = productService; } [Function("CreateProduct")] public async Task<HttpResponseData> Run( [HttpTrigger(AuthorizationLevel.Anonymous, "post")] HttpRequestData req, FunctionContext executionContext) { var logger = executionContext.GetLogger("CreateProduct"); logger.LogInformation("C# HTTP trigger function processed a request."); var product = await req.ReadFromJsonAsync<Product>(); _productService.CreateProduct(product); var response = req.CreateResponse(HttpStatusCode.OK); await response.WriteAsJsonAsync( new { Result = true, Message = $"Name: {product.Name}, Price: {product.Price}" }); return response; } }

   }