HttpContext on instances of Controllers are null in ASP.net MVC

问题

This may not be the correct way to use controllers, but I did notice this problem and hadn't figured out a way to correct it.

public JsonResult SomeControllerAction() {

    //The current method has the HttpContext just fine
    bool currentIsNotNull = (this.HttpContext == null); //which is false    

    //creating a new instance of another controller
    SomeOtherController controller = new SomeOtherController();
    bool isNull = (controller.HttpContext == null); // which is true

    //The actual HttpContext is fine in both
    bool notNull = (System.Web.HttpContext.Current == null); // which is false        

}

I've noticed that the HttpContext on a Controller isn't the "actual" HttpContext that you would find in System.Web.HttpContext.Current.

Is there some way to manually populate the HttpContextBase on a Controller? Or a better way to create an instance of a Controller?

回答1:

Controllers are not designed to be created manually like you're doing. It sounds like what you really should be doing is putting whatever reusable logic you have into a helper class instead.

回答2:

For now I'm going to do the following. This seems to be an acceptable fix...

public new HttpContextBase HttpContext {
    get {
        HttpContextWrapper context = 
            new HttpContextWrapper(System.Web.HttpContext.Current);
        return (HttpContextBase)context;                
    }
}

Where this is added to a Controller class these Controllers are inheriting from.

I'm not sure if the HttpContext being null is the desired behavior, but this will fix it in the meantime for me.

回答3:

The HttpContext, in the ControllerContext is null because it is not set when the controller is created. The contructor of the controller does not assign this property, so it will be null. Normally, the HttpContext is set to the HttpContext of the ControllerBuilder class. Controllers are created by the ControllerBuilder class, followed by the DefaultControllerFactory. When you want to create your own instance of a controller, you can use the ExecuteMethod of the controller with your own ControllerContext. You don't want to do that is a real application. When you get some more experience with the framework you will find the appropriate method to do want you want. When you need ControllerContext in Unit test, you can use a mocking framework to mock the ControllerContext or you can class faking it.

You can find a model of the request flow in asp.net mvc on this blog.

When your new to Asp.net mvc, it's worth the effort to download the source code and read an trace the route how a request is processed.

回答4:

Is it that you want to use some functionality from the controller? Or have the controller perform an action?

If it's the former, maybe that's some code that should be split out into another class. If it's the latter, you can do this to simply have that controller do a specific action:


return RedirectToAction("SomeAction", "SomeOtherController", new {param1 = "Something" });

回答5:

Are you using a controller factory? If so, how are you registering components?

I ran into this problem where I had inadvertently added an HttpContext-based dependency as a Singleton, rather than Transient in Windsor.

HttpContext was null for all but the first request. It took me a while to track down that one.

来源：https://stackoverflow.com/questions/223317/httpcontext-on-instances-of-controllers-are-null-in-asp-net-mvc

标签

asp.net-mvc

httpcontext