c# - .NET Core IHttpContextAccessor 问题

Question

我有静态助手类

public static class Current
{
    public static string Host
    {
        get { return "httpContextAccessor here"; }
    }
}

如何访问 Host 属性中的当前 HttpContext？

Answer 1

你不能也不应该。这完全违背了拥有依赖注入(inject)系统的全部目的。静态类(用于运行时数据或服务定位器)是一种反模式。

在 ASP.NET Core 中你必须注入(inject) IHttpContextAccessor在你需要的类里面。你可以制作一个非静态类并按照以下方式做一些事情:

public class RequestInformation : IRequestInformation
{
    private readonly HttpContext context;

    public RequestInformation(IHttpContextAccessor contextAccessor) 
    {
        // Don't forget null checks
        this.context = contextAccessor.HttpContext;
    }

    public string Host
    {
        get { return this.context./*Do whatever you need here*/; }
    }
}

然后在你的类库中注入(inject)它:

public class SomeClassInClassLibrary
{
    private readonly IRequestInformation requestInfo;

    public SomeClassInClassLibrary(IRequestInfomation requestInfo) 
    {
        // Don't forget null checks
        this.requestInfo = requestInfo;

        // access it
        var host = requestInfo.Host;
    }
}

请注意您的 SomeClassInClassLibrary必须用 Scoped 解决或 Transient模式，它不能是 Singleton ，因为 HttpContext仅在请求期间有效。

或者如果SomeClassInClassLibrary必须是单例，你必须注入(inject)一个工厂并解决 IRequestInformation按需(即在 Action 中)。

最后但同样重要的是，IHttpContextAccessor默认情况下未注册。

IHttpContextAccessor can be used to access the HttpContext for the current thread. However, maintaining this state has non-trivial performance costs so it has been removed from the default set of services.

Developers that depend on it can add it back as needed: services.AddSingleton<IHttpContextAccessor, HttpContextAccessor>();

来源:The IHttpContextAccessor service is not registered by default