You can get the name of a page within HttpContext via Request.Path.
Is there a way to distinguish between different requests from the same page?
That is when two different instances of yourpage.aspx make a request, how can you distinguish between the two using HttpContext?
you probably want to do this in a base Page class, but here's what i would do
public partial class Default : System.Web.UI.Page
{
private Guid _instanceID;
public Guid InstanceID
{
get { return _instanceID; }
}
/// <summary>
/// Constructor
/// </summary>
public Default()
{
this._instanceID = Guid.NewGuid();
}
}
then using the HttpContext somewhere else in your code...
if (HttpContext.Current.CurrentHandler is Default)
{
((Default)HttpContext.Current.CurrentHandler).InstanceID;
}
Nothing built into ASP.NET will allow you to differentiate different "page instances" or requests from them.
However, you can easily add a Guid to your view state to uniquely identify each page. This mechanism works fine when you are in the Page class itself. If you need to identify requests before you reach the page handler, you need to use a different mechanism (since view state is not yet restored).
The Page.LoadComplete event is a reasonable place to check if a Guid is associated with the page, and if not, create one.
If you're using authentication, would it work for you to distinguish which user submitted the page?
You could use System.Web.Httpcontext.Current.User.Identity.Name.
just throwing this out there: NInject (and other DI containers) use a scoping mechanism based on the HttpContext.Current object itself, so depending on what you're trying to do, you could attempt to retrieve a state object from the DI container and go from there.
Related
I have two screens which need to manage a list of items. The user can navigate from 1st screen to 2nd screen.
When user navigates back from 1st screen, the list of items needs to be saved to a store.
The way I was thinking to do it having a service holding the collection which gets injected in the view-models.
But the service instance must be released once user navigates back from 1st screen:
// somewhere, maybe in Application:
LifetimeManager = new ContainerControlledLifetimeManager();
Container.RegisterType<Service>(lifetimeManager);
class FirstPage()
{
ContainerControlledLifetimeManager _lifetimeManager;
public FirstPage()
{
InitializeComponent();
}
void OnDisappearing()
{
LifetimeManager.RemoveValue();
}
}
But this seems awkward, there has to be a better way to do this...
I see there's a ExternallyControlledLifetimeManager which seems it's what I need, but it would still require for FirstPage instance to get the instance of the manager and call RemoveValue. Or, I would call GC.Collect on OnDisappearing to make sure the GC collects the instance of the service, and ExternallyControlledLifetimeManager will recreate it next time it needs to be injected in the FirstPageViewModel. But calling GC.Collect seems wrong too...
Based on your comments, it sounds like you should be passing your data to your views via navigation parameters. Then each page can handle the parameters differently. Keep it simple.
var p = new NavigationParameters();
p.Add("items", MyListOfItems);
_regionManager.RequestNavigate("MyView", p);
Put your Service in another service whose job is to provide the current instance of Service.
interface IServiceProvider
{
Service CurrentInstance { get; set; }
}
Then register this one as a singleton (ContainerControlledLifetimeManager) and use it in both view models. The first one sets the instance to a new one, most likely created by some IServiceFactory, and the second one fills the instance with data.
Let's consider this page's code-behind:
public partial class Products : Page
{
private static SomeClass SharedField;
public Product()
{
// ... Some logic
}
}
Do all Products pages instances share the same SharedField, I know this is a basic concept of static fields. But in this case, really? all users can have access (and can't have their own instance of) to the same static field on the website-level?
If so, in what aspects this would used by the web developer? or is this non-recommended practice?
Yes, there will be a single instance of that static field for all users, but only within a single worker process. If you have web farms/web gardens, they will each have their own static instance. If the worker process restarts, you'll get a new static instance.
You'll have to use locking around that shared field to ensure thread safety.
As for why to use that, I'm not sure, I never do it. The best example I can give you is the built-in static HttpContext.Current, which gives you access to the Request, Response, etc.
SharedField will be available in one instance for the entire life-cycle of the web site.
To read a bit more about it, see this answer.
A better practice would be to store your object in the Application state.
Application["MyObject"] = new SomeClass();
I have an ASP.NET MVC application with an Admin area that deals with administering Companies and their child entities, such as Users and Products. The default route associated with a child entity is defined as follows:
"Admin/Company/{companyID}/{controller}/{id}/{action}"
I would like to ensure that, everywhere in the Admin area, whenever the incoming route includes companyID, that this value is automatically included in every generated URL. For example, if my User Edit page has a link defined with Html.ActionLink("back to list", "Index"), the routing system will automatically grab the companyID from the incoming route data and include it in the outgoing route, without having to explicitly specify it in the call to ActionLink.
I think there's more than one way to achieve this, but is there a preferred/best way? Does it scream for a custom route handler? Something else?
My goal is to not lose the current company context when navigating around in the sub-sections, and I don't want to use Session - that could burn me if the user opens up multiple companies in different browser windows/tabs.
Thanks in advance!
Todd,
I am using an ActionFilterAttribute in my MVC 2 application to make this happen. There may be better ways to do this:
[AttributeUsage(AttributeTargets.Class|AttributeTargets.Method, Inherited = true, AllowMultiple = true)]
sealed class MyContextProviderAttribute : ActionFilterAttribute
{
public override void OnActionExecuting(ActionExecutingContext filterContext)
{
// See if the context is provided so that you can cache it.
string myContextParam = filterContext.HttpContext.Request["myContextParam"] ;
if (!string.IsNullOrEmpty(myContextParam))
filterContext.Controller.TempData["myContextParam"] = myContextParam;
else
// Manipulate the action parameters and use the cached value.
if (filterContext.ActionParameters.Keys.Contains("myContextParam"))
filterContext.ActionParameters["myContextParam"] = filterContext.Controller.TempData["myContextParam"];
else
filterContext.ActionParameters.Add("myContextParam", filterContext.Controller.TempData["myContextParam"]);
base.OnActionExecuting(filterContext);
}
}
I am working on an ASP.NET WebForms project, and we need the ability to configure behavior throughout the application based on the current user's "group". This applies to almost all aspects of the application, including site navigation, showing/hiding certain user controls on pages, and executing custom business logic in some cases. However, the vast majority of the application behavior is shared among groups, so we've ruled out the idea of creating entirely separate apps.
Essentially, what I'm looking for is an architectural approach to implementing custom behavior in an ASP.NET WebForms application. Is there a better approach than sprinkling if/else statements throughout the code base in the view layer, the business layer, and the persistence layer?
Edit: Some examples:
If a user in in Group A, their
navigation will consist of all
navigation from Group B plus a few
additional links.
If a user is in Group A, a page will
show user controls c1, c2, and c3.
If the user is in Group B, they will
only see c1 and c3 on the same page.
If a user saves some data on a form
and they are in Group A, send a
notification email. If the user is
in Group B, send a text message
instead.
We can solve all of these specific problems, but are looking for a way to encapsulate this behavior as much as possible so it's not scattered across the code base.
Edit: There are some interesting answers related to dynamically loading user controls. Should the logic to determine which controls to load or which behavior to use based on the user's group be encapsulated in one (non-cohesive) class, e.g.:
GroupManager.GetNavigationControl(int groupId) // loads site nav control based on group
GroupManager.PerformNotification(int groupId) // sends text or email based on group
Or should this logic exist as close as possible to the location in code where it is used, and therefore be spread across the different layers of the code base?
Well there's not a ton of details to go on here, but I would suspect you might benefit from polymorphism (i.e. various interface implementations) to deal with the parts of the application that differ between user groups. An Inversion of Control container like Spring.NET can help you wire up/configure these various implementations together based on the current user role. You might also benefit from Spring's Aspect Oriented Programming API in which you can decorate methods in your business layer/data access layer so that authorization logic can be executed.
By "Groups" do you mean "Roles"? If you're talking about roles, you can set your behavior by doing something like this
If User.IsInRole("SomeRandomRole") Then
'Do some random behavioral crap
ElseIF User.IsInRole("TheCoolRole") Then
'Do some cool behavioral crap
Else
'Do generic crap
End If
Another option might be to use UserControls based on roles. So when you have a page load, it will load a usercontrol based on the role that requested it.
you could have an PlaceHolder sitting empty and call the LoadControl method from the codebehind.
Then all your user controls would match your roles
Role = Admin | UserControl = Admin.ascx
Role = User | UserControl = User.ascx
Without going into too much detail and going on about IoC and all the like, I think I'd keep it pretty simple and have a plain old factory class that you would use to return the appropriate instantiated UI elements [user controls] based on the current user making the request. In doing this, you will have all of your 'if' statements in one single location. To displense with the 'if' statements you could simply create a mapping config file or DB table that contains references to the user controls to use when a user belongs to a particular group.
Note: Both of these options will result in the creation of dynamic controls on the page which is not without its own complications but I have successfully been using dynamic controls in my apps without issue for a while now - it was just a matter of getting down and dirty with the page life-cycle more than I initially felt comfortable with.
You could also inherit from the Principal object to handle this however you would like.
Here's how I have done it in an application that has custom rules like this:
Created my own IPrincipal object that descended from my "Person" object to be able to inherit the ability to look up groups and roles and such:
public class Principal : MyNamespace.Person, IPrincipal {
}
Make the current context use my IPrincipal object:
protected void Application_AuthenticateRequest(Object Sender, EventArgs E) {
if (HttpContext.Current.User != null &&
HttpContext.Current.User.Identity.IsAuthenticated &&
HttpContext.Current.User.Identity is FormsIdentity) {
FormsIdentity id = (FormsIdentity)HttpContext.Current.User.Identity;
HttpContext.Current.User = new MyNamespace.Principal(id);
}
}
I then made static methods so that I didn't have to cast every time I wanted to get the current user like this:
public class CurrentUser {
/// <summary>
/// Is the current user authenticated
/// </summary>
static public bool IsAuthed {
get { return System.Web.HttpContext.Current.User.Identity.IsAuthenticated; }
}
/// <summary>
/// Returns the Principal object in case it is needed. Also used for other static properties of this class.
/// </summary>
static public MyNamespace.Principal User {
get {
return (MyNamespace.Principal)System.Web.HttpContext.Current.User;
}
}
}
Then you can call things like CurrentUser.User.IsInGroup().
What is the best way to call a Response.Redirect in the Model-View-Presenter pattern while adhering to correct tier separation?
One way I handled this is for the presenter to raise an event (like Succeeded or something) that the view would subscribe to. When the presenter finished it's processing, it would raise the event, which would get handled by the View. In that handler, the view would redirect to the next page.
This way, the presenter doesn't need to know anything about pages or URLs or anything. It just knows when it has completed its task and lets the view know by raising an event. You can raise different events if the presenter succeeded or failed, in case you need to redirect to different places.
I do not know whether it is the most correct way, conceptually.
But what I did in my last MVP-applications, is create a wrapper around HttpContext.Current which I called HttpRedirector.
I also created a dummy redirector for testing purposes. Both keep track of the last redirected url, so that I can check in my unit tests that the redirect actually happened when I call a method on my controller/presenter. With an IOC-container I am able to switch the implementation of IRedirector based on the environment (production/test).
The way we do it works nicely once some ground work is laid. I'm sure there are several ways to skin a cat though. (Who skins cats anyway. Cats are cute and cuddly!)
First, this will only work on the ASP.Net compiled Web Projects, not Websites.
Each page should inherit from a custom abstract base class which looks something like this:
public abstract class PageBase : Page
{
private static string _baseUrl = "/";
public static string BaseUrl
{
get { return _baseUrl; }
set { _baseUrl = value; }
}
protected static string BuildUrl(string basePath)
{
if( !string.IsNullOrEmpty(basePath) && basePath.StartsWith("~/"))
{
basePath = basePath.replace("~/", BaseUrl);
}
return basePath;
}
protected static string LoadView(string path)
{
Response.Redirect(path);
}
}
Each page also implements a page-specific interface. Each page-specific interface also inherits from a base interface:
public interface IPageBase()
{
void LoadView(string path);
}
Then it's a matter of each page defining it's own version of BaseUrl. You might want to account for querystrings/path encryption/etc.
Finally, any of your presenters (which should be referencing the page-specific interfaces) can grab the static BuildUrl() on a desired page to view and then call LoadView() with the returned path.
It depends how generic your presenters are. If your presenters are totally UI agnostic (can be reused between WinForms and WebForms) then you'll have to abstract the redirection operation. In WebForms, the redirection operation would be implemented in the view by a Response.Redirect. In WinForms, (I disclaim lots of experience with WinForms) my guess is that it would be implemented by SomeForm.Show.
One simple, off-the-top-of-my-head option would be to include in the view's interface a ShowViewX() method. You can have one for each form the view could logically redirect to. Alternatively, the view can implement an interface method like Show(ConnectedViews) where ConnectedViews is an enum that includes a value for each of the views that can be "redirected" to from a particular view. This enum would live at the presenter level.
The above approaches are specific to view-presenter pairs. You could instead implement it as a system-wide thing. The logic would be similar to above, implemented in the base view and presenter. There would be a ShowView__() for each form, or a Show(Views) method where Views is an enum of all forms.
It's a toss-up between encapsulation and DRY-ness.