I'm very new to MVC. How do I perform a Response.Clear() from within an MVC3 aspx page?
I have tried:
Response.Clear();
ViewContext.HttpContext.Response.Clear();
Neither of them seem to function at all, in that any HTML content before the statements remain in the output. The only thing that seems to work is Response.Close(), but of course that doesn't allow me to output anything afterwards.
The reason for wanting this simply a testing/debugging exercise - I just want to be able to clear the buffered output, from inline code in the aspx page, and output something else afterwards. Similar to what one could do with web forms.
Note, I don't want to perform this within the controller, as it means re-compiling every time I make a change, as well as losing session state. The point of this is to fiddle within the aspx page to avoid re-compiling each time.
Taken from your comment, that you want to mess with your code before an Action is executed and afterwards, the most ideal solution is to use custom ActionFilters:
public interface IActionFilter
{
void OnActionExecuting(ActionExecutingContext filterContext);
void OnActionExecuted(ActionExecutedContext filterContext);
}
OnActionExecuting is used to execute code before your Controller action is called, while OnActionExecuted is used after the action method has done its job.
So you hook up a custom filter like this:
public class MyCustomFilter : IActionFilter
{
public override void OnActionExecuting(ActionExecutingContext filterContext)
{
//put your custom response and shenanigans here
...
return;
}
}
After this you can decorate your controller method with this filter:
[MyCustomFilter]
public ActionResult ListSomething()
{
/* magic happens here */
}
There's a lot you can achieve here, but I suggest some further reading into this:
http://www.dotnet-tricks.com/Tutorial/mvc/b11a280114-Understanding-ASP.NET-MVC-Filters-and-Attributes.html
http://msdn.microsoft.com/en-us/magazine/gg232768.aspx
http://www.asp.net/mvc/tutorials/older-versions/controllers-and-routing/understanding-action-filters-cs
http://msdn.microsoft.com/en-us/library/gg416513(vs.98).aspx
Sidenote: If this is just for learning and debugging purposes, I'd take a look at newer mvc versions (4, 5).
In stead of focussing on Response, perhaps you should focus on what you wish to return in your controller method.
If you wish to return a full rendered View
return View("myView");
If you wish to return a PartialView
return PartialView("myPartialView");
If you wish to return a FileStream
return File(myBytes, "filename.ext");
If you wish to return a Json string,
return Json(myObject);
Try
ViewContext.HttpContext.Response.Flush();
Istead of :
ViewContext.HttpContext.Response.Clear();
Related
I have a simple scenario where if a cart is empty, I'd like to redirect to another 'page'(controller) which states the cart is empty or just send them back to the shop.
Heres my code:
public async Task<IViewComponentResult> InvokeAsync()
{
CartFunctions cartf = new CartFunctions(_logger, AppSettings, _httpContextAccessor);
Cart c = new Cart();
c = cartf.GetShopingCart();
if (c.CartItems == null)
{
// How do I get out of here to a differnet Controller
}
return View(c.CartItems);
}
If it was a controller I could return RedirectToAction
but that is not available here.
I think the main problem is i need to either get out OR return a Cartitems and I can't find a way to do both.
In the good ole days it was simple with response.redirect("Empty.aspx") but now that everything is 'easier' in MVC, it takes days of research to do the simplest things.
A view component does not sound like the ideal option do this redirect. View components are ideal for rendering some partial views. For example, rendering your cart item count or content, using the view component is a good idea.
In your case, you want to redirect to another action method when the cart is empty. You may create an action filter to do that. You can apply it on action method level or controller level as needed.
public class CheckCartValues : ActionFilterAttribute
{
public override void OnActionExecuting(ActionExecutingContext context)
{
if (yourIfConditionToCheckCartIsEmpty)
{
context.Result =
new RedirectToRouteResult(new RouteValueDictionary(new {
controller = "Shop", action = "index" }));
}
base.OnActionExecuting(context);
}
}
You can apply it on the controller level
[CheckCartValues]
public class HomeController : Controller
{
}
Make sure you do not have it on the ShopController or you will get infinite redirects. You can also update the action filter code to not do the redirect when the current request is for the ShopController if needed. I will leave it up to you :)
If you want to use an attribute you can derive from ActionMethodSelectorAttribute https://msdn.microsoft.com/en-us/library/system.web.mvc.actionmethodselectorattribute.isvalidforrequest(v=vs.118).aspx#M:System.Web.Mvc.ActionMethodSelectorAttribute.IsValidForRequest(System.Web.Mvc.ControllerContext,System.Reflection.MethodInfo).
For example you could create an attribute named CartStatus(bool isEmpty) and apply the attribute to the method(s) that need to behave differently based on cart status. Then you have your conditional logic in exactly one place (this attribute) and you can reuse it across your application. Similar to #shyju's approach but instead of redirect you just return true/false from this method for the action that is appropriate.
I'm developing an MVC3 application with EF and I wanted to make the UI fluent using jQuery ajax, the user will be able to navigate through the url, if he knows it or maybe he might receive a link pointing to a particular route, but, once the page is fully loaded it needs to be fluent, so I came up with one idea and I would like to discuss it here before I make the changes to the solution.
Here is what I came up with:
TestController.cs (Methods code has been omitted for simplicity)
public ActionResult Index() { ... }
public ActionResult Create() { ... }
[HttpPost]
public ActionResult Create(Test test) { ... }
public ActionResult Update(int testID) { ... }
[HttpPost]
public ActionResult Update(Test test) { ... }
public ActionResult Delete(int testID) { ... }
[HttpPost]
public ActionResult Delete(Test test) { ... }
So far it looks like most controllers. My views are as follows:
Views\Test\List.cshtml
Views\Test\Create.cshtml
Views\Test\Details.cshtml
Views\Test\Delete.cshtml
Now since I wanted to do it async: I've changed my List view so I could add, modify and remove from the list, so far is working like a charm. Plus, the user could still be able to navigate through the application using the url's, note that every link inside the application will perform an ajax request to do the actual work, there are no Route/Action links.
By now the application is working as expected, but now I came across something: there are views that I need to be ActionResult and PartialViewResult, that is because the user could type in the url: "/Admin/Test", which should return the full page, or could click on an anchor which will load only the content of the "/Admin/Test" and display it. To avoid the famous page inside page errors I wrote a function to send the request, and when the request arrives it selects only what I need, avoiding then the page inside page, and to duplicate views, but, the response is the whole page which, I don't need to say, it's not the best option, but since the application will be used by lan I didn't care too much about the payload of the response, but then I needed to write javascript code inside the views, so my solution was like null because using the jQuery selector to get only what I need the javascript wasn't there.
As for my new solution to solve my last solution:
I thought I might leave the original view as is, and create another view appending the word "Partial" after the original name, creating another method in the controller with the same naming convention, plus adding the new Route to my Route Table.
To wrap things up, what I need is the following:
- If the user types in "/Test" the response should be the entire page, loaded like the old days, screens flashing white and such.
- But if the user clicks the Test link in the navigation bar, the response should be async and refreshing only the content of my layout.
Any ideas? thoughts? suggestions?
In your actionmethod you can have
if (Request.IsAjaxRequest())
return PartialView("_somePartialView");
else
return PartialView("_someOtherPartialView");
I'm trying to implement a common controller in MVC3 to return various JSON feeds, example -
public class AjaxController : Controller
{
public ActionResult Feed1()
{
ViewBag.Json = LogicFacade.GetFeed1Json();
return View();
}
public ActionResult Feed2()
{
ViewBag.Json = LogicFacade.GetFeed2Json();
return View();
}
}
This class has 30+ methods in it, the problem is this requires implementing an IDENTICAL View for each of the Controller's methods (sigh) that writes out ViewBag.Json.
I'm assuming this is a routing issue but I'm struggling with that. The following didn't work -
Tried setting ViewBag.Json then using RedirectToAction() but that seems to reset ViewBag.Json.
Note JsonResult is not appropriate for my needs, I'm using a different JSON serialiser.
So the objective here is to maintain one View file but keep this class with seperate methods that are called by routing, and not a crappy switch statement implementation.
Any help appreciated.
Use the same view and just specify the name. You can store in the controller's view folder, if only used by one controller, or in the Shared view folder if used by more than one.
return View("SharedJsonView");
Another, perhaps better, solution would be to create your own result -- maybe deriving from JsonResult, maybe directly from ActionResult -- that creates the JSON response that you need. Look at the source code for JsonResult on http://www.codeplex.com/aspnet for ideas on how to do it.
I did my research but haven't found any answers.
I'm using Html.RenderAction in a masterpage ( to render page header with links specific to user permissions ). Action is decorated with OutputCache, returns partial control and gets cached as expected.
When the event happens ( let's say permissions are changed ) I want to programmatically invalidate cached partial control.
I'm trying to use RemoveOutputCacheItem method. It takes a path as a parameter. I'm trying to set the path to the action used in Html.RenderAction. That doesn't invalidate the action.
How can I programmatically invalidate the action?
Thanks
The cache for child actions is stored in the OutputCacheAttribute.ChildActionCache property. The problem is that the API generating ids for child actions and storing them in this object is not public (WHY Microsoft??). So if you try to loop through the objects in this collection you will discover that it will also contain the cached value for your child action but you won't be able to identify it unless you reverse engineer the algorithm being used to generate keys which looks something like this (as seen with Reflector):
internal string GetChildActionUniqueId(ActionExecutingContext filterContext)
{
StringBuilder builder = new StringBuilder();
builder.Append("_MvcChildActionCache_");
builder.Append(filterContext.ActionDescriptor.UniqueId);
builder.Append(DescriptorUtil.CreateUniqueId(new object[] { this.VaryByCustom }));
if (!string.IsNullOrEmpty(this.VaryByCustom))
{
string varyByCustomString = filterContext.HttpContext.ApplicationInstance.GetVaryByCustomString(HttpContext.Current, this.VaryByCustom);
builder.Append(varyByCustomString);
}
builder.Append(GetUniqueIdFromActionParameters(filterContext, SplitVaryByParam(this.VaryByParam)));
using (SHA256 sha = SHA256.Create())
{
return Convert.ToBase64String(sha.ComputeHash(Encoding.UTF8.GetBytes(builder.ToString())));
}
}
So you could perform the following madness:
public ActionResult Invalidate()
{
OutputCacheAttribute.ChildActionCache = new MemoryCache("NewDefault");
return View();
}
which obviously will invalidate all cached child actions which might not be what you are looking for but I am afraid is the only way other than of course reverse engineering the key generation :-).
#Microsoft, please, I am begging you for ASP.NET MVC 4.0:
introduce the possibility to do donut caching in addition to donut hole caching
introduce the possibility to easily expire the result of a cached controller action (something more MVCish than Response.RemoveOutputCacheItem)
introduce the possibility to easily expire the result of a cached child action
if you do 1. then obviously introduce the possibility to expire the cached donut portion.
You might want to approach this a different way. You could create a custom AuthorizeAttribute -- it would simply allow everyone -- and add override the OnCacheValidation method to incorporate your logic. If the base OnCacheValidation returns HttpValidationStatus.Valid, then make your check to see if the state has changed and if so, return HttpValidationStatus.Invalid instead.
public class PermissionsChangeValidationAttribute : AuthorizeAttribute
{
public override OnAuthorization( AuthorizationContext filterContext )
{
base.OnAuthorization( filterContext );
}
public override HttpValidationStatus OnCacheAuthorization( HttpContextBase httpContext )
{
var status = base.OnCacheAuthorization( httpContext );
if (status == HttpValidationStatus.Valid)
{
... check if the permissions have changed somehow
if (changed)
{
status = HttpValidationStatus.Invalid;
}
}
return status;
}
}
Note that there are ways to pass additional data in the cache validation process if you need to track the previous state, but you'd have to replicate some code in the base class and add your own custom cache validation handler. You can mine some ideas on how to do this from my blog post on creating a custom authorize attribute: http://farm-fresh-code.blogspot.com/2011/03/revisiting-custom-authorization-in.html
We have an a PHP application that we are converting to MVC. The goal is to have the application remain identical in terms of URLs and HTML (SEO and the like + PHP site is still being worked on). We have a booking process made of 3 views and in the current PHP site, all these view post back to the same URL, sending a hidden field to differentiate which page/step in the booking process is being sent back (data between pages is stored in state as the query is built up).
To replicate this in MVC, we could have a single action method that all 3 pages post to, with a single binder that only populates a portion of the model depending on which page it was posted from, and the controller looks at the model and decides what stage is next in the booking process. Or if this is possible (and this is my question), set up a route that can read the POST parameters and based on the values of the POST parameters, route to a differen action method.
As far as i understand there is no support for this in MVC routing as it stands (but i would love to be wrong on this), so where would i need to look at extending MVC in order to support this? (i think multiple action methods is cleaner somehow).
Your help would be much appreciated.
I have come upon two solutions, one devised by someone I work with and then another more elegant solution by me!
The first solution was to specify a class that extends MVcRouteHandler for the specified route. This route handler could examine the route in Form of the HttpContext, read the Form data and then update the RouteData in the RequestContext.
MapRoute(routes,
"Book",
"{locale}/book",
new { controller = "Reservation", action = "Index" }).RouteHandler = new ReservationRouteHandler();
The ReservationRouteHandler looks like this:
public class ReservationRouteHandler: MvcRouteHandler
{
protected override IHttpHandler GetHttpHandler(RequestContext requestContext)
{
var request = requestContext.HttpContext.Request;
// First attempt to match one of the posted tab types
var action = ReservationNavigationHandler.GetActionFromPostData(request);
requestContext.RouteData.Values["action"] = action.ActionName;
requestContext.RouteData.Values["viewStage"] = action.ViewStage;
return base.GetHttpHandler(requestContext);
}
The NavigationHandler actually does the job of looking in the form data but you get the idea.
This solution works, however, it feels a bit clunky and from looking at the controller class you would never know this was happening and wouldn't realise why en-gb/book would point to different methods, not to mention that this doesn't really feel that reusable.
A better solution is to have overloaded methods on the controller i.e. they are all called book in this case and then define your own custome ActionMethodSelectorAttribute. This is what the HttpPost Attribute derives from.
public class FormPostFilterAttribute : ActionMethodSelectorAttribute
{
private readonly string _elementId;
private readonly string _requiredValue;
public FormPostFilterAttribute(string elementId, string requiredValue)
{
_elementId = elementId;
_requiredValue = requiredValue;
}
public override bool IsValidForRequest(ControllerContext controllerContext, System.Reflection.MethodInfo methodInfo)
{
if (string.IsNullOrEmpty(controllerContext.HttpContext.Request.Form[_elementId]))
{
return false;
}
if (controllerContext.HttpContext.Request.Form[_elementId] != _requiredValue)
{
return false;
}
return true;
}
}
MVC calls this class when it tries to resolve the correct action method on a controller given a URL. We then declare the action methods as follows:
public ActionResult Book(HotelSummaryPostData hotelSummary)
{
return View("CustomerDetails");
}
[FormFieldFilter("stepID", "1")]
public ActionResult Book(YourDetailsPostData yourDetails, RequestedViewPostData requestedView)
{
return View(requestedView.RequestedView);
}
[FormFieldFilter("stepID", "2")]
public ActionResult Book(RoomDetailsPostData roomDetails, RequestedViewPostData requestedView)
{
return View(requestedView.RequestedView);
}
[HttpGet]
public ActionResult Book()
{
return View();
}
We have to define the hidden field stepID on the different pages so that when the forms on these pages post back to the common URL the SelectorAttributes correctly determines which action method to invoke. I was suprised that it correctly selects an action method when an identically named method exists with not attribute set, but also glad.
I haven't looked into whether you can stack these method selectors, i imagine that you can though which would make this a pretty damn cool feature in MVC.
I hope this answer is of some use to somebody other than me. :)