I have a value which I want to be vaild during a single request. I am not using Session, as this would make the value global for the entire navigation session.
So I have put thie value in a static field of a class. Great, but then I discovered that such fields are even more global, that is, they stay set for the entire application! This means that there could be random interaction among navigation sessions.
So the question is: is there a safe place I can put a global variable, which will be
global throughout the request
reset after the request is completed
not affected by any other request, either of the same user or by other users
Thanks
Palantir
EDIT
I'll elaborate. I have a piece of code in my master page, which I need to hide on certain conditions, of which I am aware in the controller only. I thought about setting a static variable in the controller, which then would be queried by the master page, but now I see there could be a better way...
Use HttpContext.Items - a per-request cache store. Check out this article on 4guysfromrolla for more details.
It should work fine in ASP.NET MVC. You may wish to derive your master page from a base class (either via code-behind or using the Inherits directive) and have a protected method on the base class that inspects HttpContext.Items and returns, e.g. true/false depending whether you want to display the conditional code.
TempData lasts until the next request as already noted.
But there are also two other dictionaries scoped to the single request.
{Controller,ViewPage}.ViewData
Context.Items
To communicate from controller to (master) page ViewData is probably the better choice.
Two approaches come to mind:
Create a base controller where you set this variable, and then have all your controllers inherit from that.
Use TempData - the problem here being that it sticks around for the next request. But maybe knowing that, you can work around it by using a GUID key to determine that you are, in fact, getting a new value when you need it.
I would probably go with 1).
The common way to access data in a MasterPage that is set in Controller (Action) is via ViewData["TheDataKey"] = "SomeValue".
This is relatively easy and there are a couple of ways that you can do it - depending on how your site works.
I'm interpreting your request as that you want a property or variable that exists for the duration of the request and is visible to the controller, model and master.
A static property is visible to the current application in ASP this means a load of users connecting at once, but not necessarily all of them. IIS will spawn new ASP applications as it needs to.
So the ways you can do this:
You can have a custom base class for your master page or a code-behind page (as all the WebForms stuff still works)
You can have a custom base class for your controllers.
You can get to one from the other, so:
void Page_Init( object sender, EventArgs e )
{
var ctrl = this.ViewContext.Controller as MyBaseController;
if ( ctrl != null )
{
MyLocalProp = ctrl.PropOnMyController;
}
}
This will then be available in the controller and the master page on a per Request basis.
Did you look into the tempData that is attached to the controller class? it is a simple dictionary that preserves it's value through one single request.That would meant that your data can only be accessed in the controller but that should not be a problem.
public class MyController : Controller
{
[AcceptVerbs(HttpVerbs.Get)]
public ActionResult MyAction(string id)
{
this.TempData["Message"] = "YourData";
}
[AcceptVerbs(HttpVerbs.Post)]
public ActionResult MyAction(string Id)
{
var myData = this.TempData["Message"];
}
}
This works for me. I use it only to display warning messages and stuff like that.
Related
In my asp.net mvc project I store two objects in the session when the user logs in. One is a User object (representing the logged in user) and the other is the Organisation object (representing the user's organisation).
I need one or both of these objects to be available in every action method. What's the most elegant way of dealing with this? At the moment each action takes parameters for each of these objects, with a custom model binder retrieving the objects from session. This at least encapsulates the session access but it's annoying to have the params in every method signature. Is there a better way?
Here's what most of the action methods look like.
public ActionResult Pending(IUser CurrentUser)
{
var users = CurrentUser.GetMyOrgPendingUsers();
return View(users);
}
Since you need to access IUser in almost every action you can have a base controller from where every other controller is derived.
In the base controller put IUser as a member variable and override the
OnActionExecuting() method in the base controller, in which you can put the code to access the session variables.
OnActionExecuting() will be called every time a action is called.
The Controller class has a User property. Have you considered using this rather than designing your own way to track the current user?
I'd rethink using IPrincipal here--it is very handy and allows you to work your way into the rest of the .NET authentication bits very seamlessly.
As for the problem at hand, perhaps the easiest clean course of action would be to wire them into a base controller class as protected properties. Slightly more elegant would be to create a user context class, that takes a reference to Session (or better yet, whatever base interfaces you are using in the session) and expose that class from the controller. The main advantage there is it makes it easier to change the backing store if need be and lets one encapsulate more behavior in general.
I’m building an application that monitors other systems. Now I want to implement partial view, a User Control called “status”. This control shall display status information about the application.Like:
user logged in,
How many systems online,
Latest activity.
This partial view shall be rendered in nearly all other views. How shall I pass this information to the view?
I don’t want to write
Wiewdata[“SystemsOnline”] = Helpers.CountSystemsOnline()
Wiewdata[“SystemLatestActivity”] = ………………
in all my actions.
Can I write something like Html.RenderPartial(../Shared/Status) that fist go to an action that adds the viewdata?
Or shall i access the information directly in the view trough the hepler?
I noticed that the defult LogOnUserControl view use Page.User.Identity.Name to directly access that data.
When is it ok to not pass data throug viewdata in the controller?
You have to use the ViewData class for that purpose. I do not recommend to invent tricks instead.
But you do not need to manually pass the same data from every action. Just do it in your base controller:
protected override void OnActionExecuted(ActionExecutedContext context) {
base.OnActionExecuted(context);
if (context.Result is ViewResult) {
// Pass the systems online to all views
ViewData[“SystemsOnline”] = Helpers.CountSystemsOnline();
}
}
Only a couple of lines of code and you make it available everywhere.
I'd like to get access to the current executing Controller so I can offload the return of the appropriate ActionResult onto a helper method. To this end, I'm looking for the equivalent of what I would have thought would be ControllerContext.Current but isn't. Thanks!
Edit for clarification: I've got a generic form control which is JavaScript-based but I'd like to add an option so that it works with noscript. At the moment my Controller sets the ViewData.Model to a JSON-ified Models.FormResponse<T>.
This FormReponse is set up with the status of the post and any error messages that were generated, so I'd like a GetActionResult() method which does the script/noscript check (a hidden form input) and either:
Sets the Model to the JSONed FormResponse and returns a View(), or
Serializes the FormResponse to the Session and returns a Redirect().
As this obviously changes the return value and I don't want to do the check myself every time, I need to call View or Redirect from the FormResponse's GetActionResult method in order to call this as:
return formResponse.GetActionResult();
I know with a more astronautical design this could be made even more robust but as the noscript option is not a major feature at the moment, I just need to get a quick solution working that doesn't break other things.
Update #2
The following, implemented in an ActionResult class, does the job for me. Thanks CVertex!
public override void ExecuteResult(ControllerContext context)
{
if (CMSEnvironment.NoScript)
{
Oracle.Response.Redirect(Oracle.Request.UrlReferrer.ToString(), true);
}
context.Controller.ViewData.Model = _model.ToJSON();
new ViewResult()
{
ViewName = Areas.Site.Helpers.SharedView.Service,
ViewData = context.Controller.ViewData
}.ExecuteResult(context);
}
Statics are bad for testability, and very much discouraged in MVC.
Why do you want to access the current controller and action method?
The best way to do this is to implement your own ActionFilter.
This gives you a means of intercepting requests before or after actions methods execute.
EDIT:
By intercepting the result inside OnActionExecuted of a filter, you can do your noscript/script checks and modify your ViewData accordingly for consumption by the View.
Inside OnActionExecuted, you can also do the noscript check and have complete control over the final ActionResult or the ViewData, as you please.
Or, you can write your own ActionResult that makes all these decisions.
So, your controller action ultimately does
return new MyActionResult(format_and_view_agnostic_model_object);
There doesn't appear to be a way to navigate to the current Controller from a thread. That is you could get the ControllerBuilder and you can get the MvcHttpHandler but neither then lets you access the controller instance that the handler is using.
I'm experimenting with MVC, and my question is - where I had Page_Load logic in Master Pages with WebForms, where should it go in MVC? Here's the business case:
Different Host Headers should cause different Page Titles to be displayed on the site's (one) Master Page, therefore all pages. For example, if the host header is hello.mydomain.com, the page title should be "Hello World" for all pages/views, while goodbye.mydomain.com should be "Goodbye World" for all pages/views.
If the host header is different than anything I have in the list, regardless of where in the application, it should redirect to /Error/NoHostHeader.
Previously, I'd put this in the MasterPage Load() event, and it looks like in MVC, I could do this either in every controller (doesn't feel right to have to call this functionality in every controller), or somewhere in Global.asax (seems too... global?).
Edit: I have gotten this to work successfully using the Global.asax method combined with a Controller for actually processing the data. Only problem at this point is, all of the host header information is in a database. I would normally store the "tenant" information if you will in a Session variable and only do a DB call when it's not there; is there a better way to do this?
There is no 1:1 equivalent in MVC for a reason, let's just recapitulate how to think about it the MVC way:
Model: "Pages of this site are always requested in a certain context, let's call it the tenant (or user, topic or whatever your sub domains represent). The domain model has a property representing the tenant of the current request."
View: "Render the page title depending on the tenant set in the model."
Controller: "Set the tenant in the model depending on the host header".
Keep in mind that what we want to avoid is mixing controller, view and business logic. Having controller logic in more then one place or a place, that is not called "controller" is not a problem, as long as it remains separated.
And now the good thing: You could do this "MVC style" even with Web Forms, and the solution still works with ASP.NET MVC!
You still have the request lifecycle (not the page lifecycle), so you could implement a custom HttpModule that contains this part of the controller logic for all requests. It handles the BeginRequest event, checks for the host header, and stores the tenant to something like HttpContext.Current.Items["tenant"]. (Of course you could have a static, typed wrapper for this dictionary entry.)
Then all your model objects (or a model base class, or whatever is appropriate for your solution) can access the HttpContext to provide access to this information like this:
public string Tenant
{
get { return HttpContext.Current.Items["tenant"]; }
}
Advantages:
You have separated cause (host header) and effect (rendering page title), improving maintainability and testability
Therefore you could easily add additional behavior to your domain model based on this state, like loading content from the database depending on the current tenant.
You could easily make more parts of the view depend on the tenant, like CSS file you include, a logo image etc.
You could later change the controller logic to set the tenant in the model not only based on the sub domain, but maybe based on a cookie, a referrer, search term, user agent's language, or whatever you can think about, without modifying any of your code depending on the model.
Update re your edit: I don't like the idea of holding the state in the session, especially if your session cookie might apply not only to each sub domain, but to all domains. In this case you might serve inconsistent content if users visted another sub domain before. Probably the information in the database that is mapping host headers to tenants won't change very often, so you can cache it and don't need a database lookup for every request.
You could create a base controller that supplied the correct ViewData to your MVC Master Page View, then derive each of your actual controllers from that one. If you put the logic into the ActionExecuting method, you should be able to generate an exception or redirect to an error page if necessary.
You are thinking too "WebForms" and not enough MVC. A master page is just a wrapper of your view, and it should only contain layout html. You can send stuff to your master, but it's a one way road and you should strive for agnostic views. Bottom line: forget about the events that WebForms had as they aren't going to be used here.
Since you are dealing with Host headers I suppose you could put it in the Global.asax...great now I'm confused :P
Stolen code from http://forums.asp.net/t/1226272.aspx
protected void Application_BeginRequest(object sender, EventArgs e)
{
string host = string.Empty;
if (this.Request.ServerVariables["HTTP_HOST"] == this.Request.Url.DnsSafeHost)
{
host = this.Request.Url.DnsSafeHost;
}
else
{
Regex regex = new Regex("http://[^/]*.host/([^/]*)(/.*)");
Match match = regex.Match(this.Request.Url.AbsoluteUri);
if (match.Success)
{
host = match.Groups[1].Value;
Context.RewritePath(match.Groups[2].Value);
}
}
// Match the host with the portal in the database
...
}
What you need is here http://www.asp.net/mvc/tutorials/passing-data-to-view-master-pages-cs
I'm using a few (2 or 3) master pages in my ASP.NET MVC application and they must each display bits of information from the database. Such as a list of sponsors, current fundings status etc.
So my question was, where should I put these master-page database calling code?
Normally, these should goes into its own controller class right? But then that'd mean I'd have to wire them up manually (e.g. passing ViewDatas) since it is out of the normal routing framework provided by the MVC framework.
Is there a way to this cleanly without wiring ViewData passing/Action calls to master pages manually or subclassing the frameworks'?
The amount of documentation is very low... and I'm very new to all this including the concepts of MVC itself so please share your tips/techniques on this.
One way to do this is to put in the masterpage view the hook for the ViewData and then you define a BaseController : Controller (or multiple base classes) where you do all the db calls you need.
What you wanna do is quite the same thing described in this articles.
I hope this helps!
Regards
Great question. You have several options available to you.
Have a jQuery call on your masterpage that grabs the data you need from a controller and then populate your fields using jQuery again.
Your second option is to create user controls that make their own calls to the controller to populate their information.
I think the best choice is creating controls for the region of your masterpage that has data that needs to be populated. Thus leaving your masterpage to strictly contain design elements. Good luck.
If you don't mind strongly typed view data, you can put all the master page data in a common base class for viewData. You can set this data in the base class's constructor. All your views requiring additional data will then need strongly typed viewdata that inherits from this base class.
To allow a call to View() in your controllers without any explicit viewdata you can override View in your ControllerBase:
protected override ViewResult View(string viewName, string masterName, object model)
{
if (model == null)
{
model = new ViewDataBase();
}
return base.View(viewName, masterName, model);
}