blocks|key|799334|text|为什么不使用appsettings.json来存储这些信息，然后使用内置的DI将其注入到中间件中呢？|type|unstyled|depth|inlineStyleRanges|entityRanges|data|799335|appsettings.json|offset|length|style|BOLD|799336|{
++++"MiddlewareConfiguration":
++++{
++++++++"MiddlewareValue":42,
++++}
}|code-block|syntax|javascript|799337|Startup.cs|799338|public+IServiceProvider+ConfigureServices(IServiceCollection+services)
{
++++services.Configure<MiddlewareConfiguration>(configuration.GetSection("MiddlewareConfiguration"));
}|799339|MiddlewareConfiguration.cs|799340|public+class+MiddlewareConfiguration
{
++++public+int+MiddlewareValue+{+get;+set;+}
}|799341|然后，您可以将其插入到中间件中，例如：|799342|public+async+Task+Invoke(HttpContext+context,+IOptions<MiddlewareConfiguration>+config)|799343|entityMap^0|0|0|G|0|0|0|A|0|0|0|Q|0|0|0|0^^$0|@$1|2|3|4|5|6|7|10|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|11|8|@$D|12|E|13|F|G]]|9|@]|A|$]]|$1|H|3|I|5|J|7|14|8|@]|9|@]|A|$K|L]]|$1|M|3|N|5|6|7|15|8|@$D|16|E|17|F|G]]|9|@]|A|$]]|$1|O|3|P|5|J|7|18|8|@]|9|@]|A|$K|L]]|$1|Q|3|R|5|6|7|19|8|@$D|1A|E|1B|F|G]]|9|@]|A|$]]|$1|S|3|T|5|J|7|1C|8|@]|9|@]|A|$K|L]]|$1|U|3|V|5|6|7|1D|8|@]|9|@]|A|$]]|$1|W|3|X|5|J|7|1E|8|@]|9|@]|A|$K|L]]|$1|Y|3|-4|5|6|7|1F|8|@]|9|@]|A|$]]]|Z|$]]

Why don't you use the appsettings.json to store this information and then use the built-in DI to inject it into your middleware?

appsettings.json

<pre><code>{
 "MiddlewareConfiguration":
 {
 "MiddlewareValue":42,
 }
}
</code></pre>

Startup.cs

<pre><code>public IServiceProvider ConfigureServices(IServiceCollection services)
{
 services.Configure&lt;MiddlewareConfiguration&gt;(configuration.GetSection("MiddlewareConfiguration"));
}
</code></pre>

MiddlewareConfiguration.cs

<pre><code>public class MiddlewareConfiguration
{
 public int MiddlewareValue { get; set; }
}
</code></pre>

You can then inject it into your middleware, e.g.:

<pre><code>public async Task Invoke(HttpContext context, IOptions&lt;MiddlewareConfiguration&gt; config)
</code></pre>

blocks|key|325609|text|通常情况下，扩展方法不适用于此。扩展方法是静态的，因此只能访问其他静态成员。然而，ASP.NET核心在设计上不使用任何静力学，并且广泛使用依赖注入来管理对象的生存期和访问依赖项。|type|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|data|325610|因此，通常情况下，正确的方法是将扩展方法移动到某种非静态助手对象中，然后将其注入到需要访问它的位置。当然，这将不允许您在需要时轻松地调用它，而是要求您显式地依赖它(这是依赖注入的点之一)。|325611|话虽如此，你的明确案例有点不同。从您的链接拉请求中可以看到，您的扩展方法如下所示(注意，我在这里合并了两个方法，以表明这一点)：|325612|public+static+async+Task+ShipAsync(this+Exception+exception,+HttpContext+context)
{
++++await+MessageShipper.ShipAsync(
++++++++ElmahIoMiddleware.ApiKey.AssertApiKeyInMiddleware(),
++++++++ElmahIoMiddleware.LogId.AssertLogIdInMiddleware(),
++++++++exception.Message,+context,+new+ElmahIoSettings(),+exception);
}|code-block|syntax|javascript|325613|这有什么关系？因为你要通过HttpContext。HTTP上下文允许我们访问依赖注入。因此，我们实际上可以从依赖项注入容器中解决问题：|style|CODE|325614|public+static+async+Task+ShipAsync(this+Exception+exception,+HttpContext+context)
{
++++var+elmahIoConfig+=+context.RequestServices.GetService<ElmahIoConfiguration>();

++++await+MessageShipper.ShipAsync(
++++++++elmahIoConfig.ApiKey,
++++++++elmahIoConfig.LogId,
++++++++exception.Message,+context,+new+ElmahIoSettings(),+exception);
}|325615|现在，您只需要确保在注册中间件时ElmahIoConfiguration得到了正确的填充。请注意，我在这里不请求中间件实例，因为中间件通常不通过依赖项注入注册。引入一个单独的对象更有意义，然后您可以将该对象注入中间件并在那里进行初始化。|325616|在您的示例中，您确实应该将中间件配置移到您的应用程序设置中，并使用IOptions<>模式在ConfigureServices级别配置它。在Configure中将中间件添加到管道中时，配置中间件不再是ASP.NET+Core+2中的常见模式。|325617|entityMap|0|LINK|mutability|MUTABLE|url|https://learn.microsoft.com/en-us/aspnet/core/fundamentals/dependency-injection|1|https://github.com/elmahio/Elmah.Io.AspNetCore/pull/2^0|1X|4|0|0|0|J|5|1|0|0|D|B|0|0|G|K|0|X|A|1A|H|1Y|9|0^^$0|@$1|2|3|4|5|6|7|16|8|@]|9|@$A|17|B|18|1|19]]|C|$]]|$1|D|3|E|5|6|7|1A|8|@]|9|@]|C|$]]|$1|F|3|G|5|6|7|1B|8|@]|9|@$A|1C|B|1D|1|1E]]|C|$]]|$1|H|3|I|5|J|7|1F|8|@]|9|@]|C|$K|L]]|$1|M|3|N|5|6|7|1G|8|@$A|1H|B|1I|O|P]]|9|@]|C|$]]|$1|Q|3|R|5|J|7|1J|8|@]|9|@]|C|$K|L]]|$1|S|3|T|5|6|7|1K|8|@$A|1L|B|1M|O|P]]|9|@]|C|$]]|$1|U|3|V|5|6|7|1N|8|@$A|1O|B|1P|O|P]|$A|1Q|B|1R|O|P]|$A|1S|B|1T|O|P]]|9|@]|C|$]]|$1|W|3|-4|5|6|7|1U|8|@]|9|@]|C|$]]]|X|$Y|$5|Z|10|11|C|$12|13]]|14|$5|Z|10|11|C|$12|15]]]]

In general, this won’t work with extension methods. Extension methods are static and as such can only access other static members. ASP.NET Core however is by design not using any statics and extensively uses <a href="https://learn.microsoft.com/en-us/aspnet/core/fundamentals/dependency-injection" rel="nofollow noreferrer">dependency injection</a> to manage the lifetime of objects and to access dependencies.

So usually, the proper way would be to move your extension method into some kind of non-static helper object which you can then inject where you need to access it. Of course, this will not allow you to easily call it wherever you need it but requires you to explicitly depend on it (which is one of the points of dependency injection).

That being said, your explicit case is a bit different. As I could see from your <a href="https://github.com/elmahio/Elmah.Io.AspNetCore/pull/2" rel="nofollow noreferrer">linked pull request</a>, your extension method looks like this (note, I combined two methods here to make it clear):

<pre><code>public static async Task ShipAsync(this Exception exception, HttpContext context)
{
 await MessageShipper.ShipAsync(
 ElmahIoMiddleware.ApiKey.AssertApiKeyInMiddleware(),
 ElmahIoMiddleware.LogId.AssertLogIdInMiddleware(),
 exception.Message, context, new ElmahIoSettings(), exception);
}
</code></pre>

Why does that matter? Because you are passing <code>HttpContext</code>. And the HTTP context gives us access to dependency injection. So we can actually resolve things from the dependency injection container:

<pre><code>public static async Task ShipAsync(this Exception exception, HttpContext context)
{
 var elmahIoConfig = context.RequestServices.GetService&lt;ElmahIoConfiguration&gt;();

 await MessageShipper.ShipAsync(
 elmahIoConfig.ApiKey,
 elmahIoConfig.LogId,
 exception.Message, context, new ElmahIoSettings(), exception);
}
</code></pre>

Now, you just need to make sure that <code>ElmahIoConfiguration</code> gets filled properly when you register the middleware. Note that I am not requesting the middleware instance here because middlewares are usually not registered with dependency injection. It makes more sense to introduce a separate object which you can then inject into the middleware and initialize there.

In your case, you should really move the middleware configuration into your application settings and use the <code>IOptions&lt;&gt;</code> pattern to configure it at <code>ConfigureServices</code> level. Configuring middleware as you add it to the pipeline in <code>Configure</code> is not really a common pattern in ASP.NET Core 2 anymore.

I've developed a piece of ASP.NET Core middleware. I've simplified the middleware in this post, to make the problem clearer.

The middleware is configured in <code>Startup.cs</code> like this:

<pre class="lang-cs prettyprint-override"><code>public void Configure(IApplicationBuilder app, IHostingEnvironment env)
{
 ...
 app.UseMyMiddleware(42);
 ...
}
</code></pre>

The integer (<code>42</code>) is stored in the middleware instance and everything is fine.

Now I want to create some helper methods as extension methods:

<pre class="lang-cs prettyprint-override"><code>public static int Add(this int i)
{
 return i + TODO;
}
</code></pre>

I would like the method to add the value of <code>i</code> to the value (<code>42</code>) sent to the middleware.

Currently I've saved the value of <code>42</code> in a public static var inside the middleware and access this from my extension method:

<pre class="lang-cs prettyprint-override"><code>public static int Add(this int i)
{
 return i + MyMiddleware.Value;
}
</code></pre>

I don't like this solution for various reasons. Any ideas to how this can be solved in a better way would be highly appreciated.

Using middleware config from extension methods in ASP.NET Core

翻译质量差，导致语言生硬或混乱。

没有提供实际的解决方法或示例。

解答不清晰，无法理解或解决问题。

页面排版不美观，阅读体验差。

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我已经开发了一段ASP.NET核心中间件。我在这篇文章中简化了中间件，以使问题变得更清楚。中间件在Startup.cs中配置如下：public void Configure(IApplicationBuilder app, IHostingEnvironment env){    ...    app.UseMyMid...

问从ASP.NET内核的扩展方法中使用中间件配置
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