[转]How to use IHttpContextAccessor in static class to set cookies

本文转自：http://stackoverflow.com/questions/37329354/how-to-use-ihttpcontextaccessor-in-static-class-to-set-cookies

While i would advise staying away from static class scenarios like this, it is still possible to achieve what you are asking for.

In the Startup.ConfigureServices method you can call services.BuildServiceProvider() to get the IServiceProvider to resolve the type you seek. It's a bit of a hack but it works.

Assuming a static class like...

public class MyStaticHelperClass {
    private static IHttpContextAccessor httpContextAccessor;
    public static void SetHttpContextAccessor(IHttpContextAccessor  accessor) {
        httpContextAccessor = accessor;
    }

    public static void addReplaceCookie(string cookieName, string cookieValue) {
        var HttpContext = httpContextAccessor.HttpContext;
        if (HttpContext.Request.Cookies(cookieName) == null) {
            // add cookie
            HttpCookie s = new HttpCookie(cookieName);
            s.Value = cookieValue;
            s.Expires = DateTime.Now.AddDays(7);
            HttpContext.Response.Cookies.Add(s);
        } else {
            // ensure cookie value is correct
            HttpCookie existingSchoolCookie = HttpContext.Request.Cookies(cookieName);
            existingSchoolCookie.Expires = DateTime.Now.AddDays(7);
            existingSchoolCookie.Value = cookieValue;
            HttpContext.Response.Cookies.Set(existingSchoolCookie);
        }
    }
}

You would configure your class during start up

public IServiceProvider ConfigureServices(IServiceCollection service) {
    services.AddTransient<IMyService, MyService>();
    services.AddMvc();

    //this would have been done by the framework any way after this method call;
    //in this case you call the BuildServiceProvider manually to be able to use it
    var serviceProvider = services.BuildServiceProvider();

    //here is where you set you accessor
    var accessor = serviceProvider.GetService<IHttpContextAccessor>()
    MyStaticHelperClass.SetHttpContextAccessor(accessor);

    return serviceProvider;
}

Now with that done. I would still strongly advise converting your static class into a service whose concrete implementation would use the IHttpContextAccessor as a dependency that can be injected via its constructor.

public interface ICookieService {
    void AddReplaceCookie(string cookieName, string cookieValue);
}

public class CookieService : ICookieService {
    IHttpContextAccessor httpContextAccessor;
    public CookieService(IHttpContextAccessor httpContextAccessor) {
        this.httpContextAccessor = httpContextAccessor;
    }
    public void AddReplaceCookie(string cookieName, string cookieValue) {
        var HttpContext = httpContextAccessor.HttpContext;
        if (HttpContext.Request.Cookies(cookieName) == null) {
            // add cookie
            HttpCookie s = new HttpCookie(cookieName);
            s.Value = cookieValue;
            s.Expires = DateTime.Now.AddDays(7);
            HttpContext.Response.Cookies.Add(s);
        } else {
            // ensure cookie value is correct
            HttpCookie existingSchoolCookie = HttpContext.Request.Cookies(cookieName);
            existingSchoolCookie.Expires = DateTime.Now.AddDays(7);
            existingSchoolCookie.Value = cookieValue;
            HttpContext.Response.Cookies.Set(existingSchoolCookie);
        }
    }
}

...that could then be registered with the Services collection...

public void ConfigureServices(IServiceCollection service) {
    services.AddTransient<ICookieService, CookieService>();
    services.AddMvc();
}

...and be available for injection into classes that have need of it's use.

public class SomeClassThatNeedCookieServicesController : Controller {
    ICookieService cookieService;

    public SomeClassThatNeedCookieServicesController(ICookieService cookieService) {
        this.cookieService = cookieService;
    }
}

This is how I do it to manage session cookies in my applications.