在非控制器类中使用依赖注入？ [英] Using dependency injection in a non-controller class?

问题描述

我有一个DocumentRenderer类，该类调用外部API。 DocumentRenderer需要一个AccessKey，该密钥存储在我的appsettings.json配置文件中。我想要一个新实例化的DocumentRenderer对象，默认情况下使用配置文件中指定的AccessKey。但是，我不知道如何在startup.cs之外实现此目标。 （我正在使用ASP.NET Core）

I have a DocumentRenderer class, which calls an external API. The DocumentRenderer requires an AccessKey, which is stored in my appsettings.json config file. I want a newly instantiated DocumentRenderer object to, by default, use the AccessKey specified in the config file. However, I can't figure out how to achieve this outside of startup.cs. (I'm using ASP.NET Core)

这是到目前为止我尝试过的内容：

Here's what I've tried so far:

已添加到appsettings.json的DocumentRenderer：

Added DocumentRenderer to appsettings.json:

"DocumentRenderer": {
    "AccessKey": "<key>",
    "EndpointUrl": "<url>",
    "OutputFormat" :  "pdf" 
}

创建了一个 DocumentRendererOptions POCO：

Created a "DocumentRendererOptions" POCO:

public class DocumentRendererOptions
{
    public string AccessKey { get; set; }
    public string EndpointUrl { get; set; }
    public string OutputFormat { get; set; }
}

将DocumentRendererOptions注册为单例服务，并将appsettings.json中的选项绑定到它在startup.cs的ConfigureServices方法中：

Registered DocumentRendererOptions as a singleton service and bound the options from appsettings.json to it in the ConfigureServices method of startup.cs:

public void ConfigureServices(IServiceCollection services)
{
    services.AddSingleton<DocumentRendererOptions>();
    services.Configure<DocumentRendererOptions>(options => Configuration.GetSection("DocumentRenderer").Bind(options));
}

最后，我有了我的DocumentRenderer类：

Finally I have my DocumentRenderer class:

public class DocumentRenderer
{
    private readonly string _endpointUrl;
    private readonly string _accessKey;
    private readonly string _outputFormat;

    public DocumentRenderer()
    {
    }

    public DocumentRenderer(IOptions<DocumentRendererOptions> options)
    {
        _accessKey = options.Value.AccessKey;
        _endpointUrl = options.Value.EndpointUrl;
        _outputFormat = options.Value.OutputFormat;
    }
}

我错误地认为这将允许我实例化一个新的具有默认选项的DocumentRenderer对象，但是显然缺少某些东西。

I incorrectly assumed this would allow me to instantiate a new DocumentRenderer object with the default options, but obviously something is missing.

到目前为止，我读过的每篇文章都只是在谈论使用此方法和控制器并允许DI做

Every article I've read so far just talks about using this method with a controller and allowing DI to do the rest, but the DocumentRenderer isn't a controller.

作为一个临时修复，我刚刚将DocumentRendererOptions设为静态，然后在启动时分配了值，但这并没有。似乎是最好的解决方案

As a temporary fix I've just made DocumentRendererOptions static, then assigned the values in startup, but this doesn't seem like the best solution

推荐答案

将 DocumentRenderer 注册为以下服务好，这样框架就会为您实例化

register the DocumentRenderer with services as well so the framework will instantiate it for you

public void ConfigureServices(IServiceCollection services)
{
    // Adds services required for using options.
    services.AddOptions();

    // Registers the following lambda used to configure options.
    services.Configure<DocumentRendererOptions>(Configuration.GetSection("DocumentRenderer"));

    //register other services
    services.AddSingleton<DocumentRenderer>();
}

来源：使用选项和配置对象

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