依赖项注入在Azure函数中缺少注册时注入null [英] Dependency injection injecting null when missing registration in Azure functions

问题描述

我正在将null注入我的构造函数中，该构造函数具有我忘记注册的依赖项.

I'm getting null injected into my constructor that has a dependency which I forgot to register.

在下面的示例中，当您忘记在启动类中注册IDepencency时，依赖关系将为null

In the below example dependency would be null when you forget to register IDepencency in the startup class

public class AzureFunction {
    public AzureFunction(IDepencency dependency) {

    }
}

我希望它的工作方式与.net core DI中的工作相同.

I expected it to work the same as in .net core DI.

这是预期的行为吗?我是否可以更改设置以启用抛出异常?

Is this expected behavior? And can I maybe change a setting to enable throwing exceptions?

在阅读了HariHaran的答案之后，我意识到这只是在子依赖中发生.这是一个可重现的示例:

After reading HariHaran's answer, I realized it's only happening in a sub-dependency. This is a reproducible example:

public interface IClass1 { }

public class Class1 : IClass1
{
    private readonly IClass2 _class2;

    public Class1(IClass2 class2)
    {
        _class2 = class2; // This will be null
    }
}

public interface IClass2 { }

public class Class2 : IClass2 { }

public class Function1
{
    private readonly IClass1 _class1;
    public Function1(IClass1 class1)
    {
        _class1 = class1;
    }

    [FunctionName("Function1")]
    public async Task<HttpResponseMessage> Run(
        [HttpTrigger(AuthorizationLevel.Anonymous,"post", Route = null)]
        HttpRequestMessage req,
        ILogger log)
    {
        log.LogInformation("C# HTTP trigger function processed a request.");
        return req.CreateResponse(HttpStatusCode.Accepted);

    }
}

并将其放在functionsStartup中:

[assembly: FunctionsStartup(typeof(Startup))]
namespace FunctionApp2
{
    public class Startup : FunctionsStartup
    {
        public override void Configure(IFunctionsHostBuilder builder)
        {
            builder.Services.AddSingleton<IClass1, Class1>();
            //builder.Services.AddSingleton<IClass2, Class2>(); // Leave this commented
        }
    }

}

推荐答案

不，这不是预期的行为.默认情况下，func host会抛出

No this is not the expected behaviour. The func host by default will throw

在尝试激活'FunctionApp2.Function1'时无法解析类型为'FunctionApp2.IClass1'的服务.

Unable to resolve service for type 'FunctionApp2.IClass1' while attempting to activate 'FunctionApp2.Function1'.

这是简单的可复制代码.

Here's the simple reproducable piece of code.

public class Function1
{
    private readonly IClass1 _class1;
    public Function1(IClass1 class1)
    {
        _class1 = class1;
    }
    [FunctionName("Function1")]
    public async Task<HttpResponseMessage> Run(
        [HttpTrigger(AuthorizationLevel.Anonymous,"post", Route = null)]
        HttpRequestMessage req,
        ILogger log)
    {
        log.LogInformation("C# HTTP trigger function processed a request.");
        return req.CreateResponse(HttpStatusCode.Accepted);

    }
}

在functionsStartup中，我评论了我的注册

In the functionsStartup i commented my registration

[assembly: FunctionsStartup(typeof(Startup))]
namespace FunctionApp2
{
    public class Startup : FunctionsStartup
    {
        public override void Configure(IFunctionsHostBuilder builder)
        {
            //builder.Services.AddSingleton<IClass1, Class1>();

        }
    }

}

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