Here is some weird behaviour that is consistent across different actions and views in my entire website:
Whenever I POST to some action method and Model.IsValid is false, I return the view. Whenever Html.Action() is called in the view that is returned I get this exception:
(System.Web.HttpException): No matching action was found on controller 'xyz'.
This can happen when a controller uses RouteAttribute for routing,
but no action on that controller matches the request.
I'm using Attribute Routing.
public class RouteConfig
{
// REGISTER ROUTES
public static void RegisterRoutes(RouteCollection routes)
{
routes.MapMvcAttributeRoutes();
}
}
So even though the Html.Action call worked the first time in the GET action method return View(), Html.Action always throws this exception after POST return View(). This is a general pattern across my website.
Wtf? Any ideas what's gone wrong here? The only thing I can think of is that I added more routes over time and now it's confused. How would I fix or test that if that's the case?
It just occurred to me that I have many routes/action methods where the get and post versions of routes for action methods are identical except for the GET or POST attribute on the action method. I previously made sure every route was completely unique because I was getting some ambiguity but changed it back to the same routes for get and post action methods, the only difference being the get or post attribute... I'm becoming convinced it's a routing issue but I don't know what's wrong specifically. I have route attributes on hundreds of action methods.
I have never seen anything as subtle as this before and have no idea even how to start solving something like this. I have no idea if it's simple or complicated, if it's my code or the framework. Any help would be greatly appreciated.
UPDATE:
Some sample code, not sure it will help, because the same things happens as a pattern across many utterly different action methods and views, regardless of GET, POST, authorized, unauthorized, in a role or not, antiforgerytoken...
Standard Html.Action called from a view. Works fine most of the time. (Different overloads make no difference.)
#Html.Action("CategoryDropDowns", "Category")
Here is what gets called (exactly what gets returned makes no difference, could be a ViewResult, could be an int).
// GET: /category/category-drop-downs
[HttpGet]
[Route("category/category-drop-downs")]
public ViewResult CategoryDropDowns()
{
}
If validation fails the view is returned:
public ActionResult CreateListing(ListDetails listDetails)
{
if (ModelState.IsValid)
{
}
else
{
return View("List", model);
}
}
And upon debugging through the view that gets returned, the call to Html.Action that worked fine the first time throws the exception. Same thing happens as a pattern across my website. Return View(), hit the Html.Action, bang, exception. Every time.
Remove the [HttpGet] attribute from child actions!
The problem was that Html.Action() always seemed to hit an exception not after a GET, return View(), but a POST, return View().
Ages ago I went through my whole site and marked every action method that wasn't a post with the [HttpGet] attribute. I didn't realise this would cause a problem. Always test!
Removing the [HttpGet] attribute from action methods called from Html.Action() has solved the problem.
Related
I am trying to build sth pretty simple, but I try to do it the correct way. But I struggle to figure out what is best.
I have a process chain where the user has to fill in some fields in different forms. Sometimes it depends from the user inputs which form the user is shown next.
[HttpGet]
public IActionResult Form1(Form1Vm f1vm)
{
return View(f1vm);
}
[HttpPost]
[ActionName("Form1")]
public IActionResult Form1Post(Form1Vm f1vm)
{
//process the data etc
//prepare the new viewmodel for the next form view (f2vm)
//Option1:
return View("Form2", f2vm);
//Option2:
return RedirectToAction("Form2", f2vm);
//for Option 2 I would need an additional HttpGet Action Method in which I
//would have to call Modelstate.Clear(); in order to not have the
//immediate validation errors on page load
//also all the properties of my viewmodel are passed as get parameters
//what looks pretty nasty for me
}
//More form views action methods should be added here...:
What is the better way? As mentioned in my comments above I have quite a big disadvantage for using the RedirectToAction option. However if I use the direct View(); call, I don't take care on https://en.wikipedia.org/wiki/Post/Redirect/Get and the user cannot simply refresh a page without getting a warning that his form is submitted once again.
Do I miss another way or don't see something obvious?
Edit: I just thought about a 3rd way, which I have seen quite often: Not transfering the whole VM to a HttpGet method but only the ID. I'd then have to load all the data stored previously directly from the db, map it again to my new VM and then call the View(); with this VM. Right now I think this is the "best" solution, however I feel like it is pretty laborious...
As per the dicussions, I would suggest using depending on your preference :
1) Save to db at the end of each form post and as you suggested use the I'd to redirect to a GET.
2) Depending on the the number of form pages and your requirements, retrieving values that a form needs on the get would be standard practice. This ensures that if a user drops off a form at any stage you can then start them off where they left off.
3) I wouldn't setup the viewmodel for the next form in the post of the previous. Generally as part of the single responsibility principle you want to ensure that your methods have only one reason to change.
4) PostRedirectGet pattern should be implemented with this to ensure data is not saved multiple times if a user refreshes after a post.
I have the following method in my controller, using C# MVC with Attribute roouting:
[Route("")]
[Route("/something-else")]
public IActionResult Index(){
}
Im using two different routes to access this functionallity, since i want customers with bookmarks to the previous implementation to work.
The problem is that i cant specify which of these Routes will be the default one when i issue the action like this:
<a asp-controller="FOO" asp-action="Index">
Everythiing works as expected, both URLs work, but i cant specify which of these routes will be used when navigated to by the action, via the action above.
I would like that the first route be used everytime i navigate to this action, except when someone explicitly writes the old url into the browser.
Are there any default attributes to the [Route("")] tag?
The RouteAttribute class has an Order property. From the docs:
Gets the route order. The order determines the order of route execution. Routes with a lower order value are tried first.
For example:
[Route("/something-else", Order = 1)]
[Route("", Order = 2)]
public IActionResult Index(){
}
As an aside, I would strongly discourage you from serving the same page with multiple URLs. Google's indexing will give you worse ranking because of it. Instead, consider returning a redirect to the new URL instead.
I'm getting a
No route matches the supplied values
while trying to return a RedirectToAction("Action", "Controller"). The method signature says "actionName" and "ControllerName". I'm assuming actionName is the method name in the Controller, Am I correct? For ControllerName I'm using the Controller File Name without the Controller Sufix. Ex.:
return RedirectToAction("Index", "WebApp")
where Index is a method of WebAppController and the command is being issued from a method of AnotherController
Both the caller controller and the called one are on the same Controllers directory on the same application.
I'm cofused because in this ASP.net MVC application there is also Route attributes and Action attributes where you can put names on methods, different than the real method name. In my case I have no Route["Name"] nor [httpXXX("route", Name="dasdasdas")] configured for the methods involved in my attempt.
I have been reading MS docs and some examples but It appears I'm doing the thing right but for strange reasons it's not working. I even tried using Redirect("Controller/Action") and with it the problem vanishes but the new problem is this way of redirect doesn't support passing data parameters to the target route.
At this point I'm not working with Action links in Views, different from Form related ones.
I would really appreciate if at least anyone can give me a hint about where can I find info.
The right way to call an action from a different controller is the one I was using:
return RedirectToAction("AnActionMethodName", "AControllerWithoutControllerSufix"[, object values]);
My problem, after several hour spent was that I added two useMvc calls in the Startup.Configure(...)method:
app.UseMvc();
app.UseMvc(routes =>
{
routes.MapRoute(
name: "default",
template: "{controller=MyApp}/{action=Index}/{id?}");
});
This was due to copy + paste of code. It was obviously confusing the MVC component in charge of attending the redirection part, as the right way I supose is tho use only one. (I'm newbie on .Net Platform and its frameworks)
Anyway I leave this as a reminder about the risks and consequences of copying and pasting code. At some point something weird can happen to your app and the cause can be a simple copy + paste error.
I'm having difficulty grasping the concept of MVC within .NET. I'm creating a basic Blog application, mainly to gain insight and skills with MVC. I just don't quite get some of it. The part I am currently unclear about is the relationship between a Controller and View. It would clear the matter up if someone would answer me this.
I have a View called TestA which corresponds to my Controller ControllerTestA. Now I've added the following inside the ControllerTestA.
public ActionResult TestA (){ //do something }
Now I need to know if all my postbacks in whatever form from view TestA will have to go through my TestA Controller method. So essentially I could have different postback with different parameters for different reasons. Some in use with one postback and others in use for another. Is that how it is done?
Would love some assistance here.
You are missing a crucial part of the relationship here, which is routing. You are speaking in terms of WebForms using terms like Postback; don't do that because you'll end up confusing yourself.
The best way to think about MVC is in Requests and Responses.
Let's look at how a request (high level) happens in an MVC application.
Request
Request hits the server with a url ex. /hello/world
That url is used to match any entries in your route table
When a match is found, that route defines basic values like what controller and action should be called.
The controller is created, and that action is called with the route values and other request properties (querystring, session, etc...).
Response
We are now in the controller action, run the code you need to fulfill the request
Pass the data to the View
The view is determined by convention and your ViewEngine
The view is then rendered and written to the response.
The request/response is finished.
Note
This whole process is determined by the route, and the relationship between the controller and view are trivial. Where the form is posted to is determined by you in the view by using helper methods that determine what route to hit in the next request/response flow.
Some Helper Methods.
#Url.Action("index", "home");
#Html.ActionLink("index", "home")
#using (Html.BeginForm("create", "home")) { }
To sum it all up, the relationship between the controller action and view is really facilitate by your routes. Once you have a grasp of how to create them, then you will better understand how to manage the interaction of your application. Hope that helps. :)
There is no such thing as "Postback" in MVC. In contrast to WebForms, a view only renders HTML to be sent to the browser. As soon as any type of request is issued by the browser, it goes to the controller, not to the view.
As for the relationships:
If you define a TestAController (note: Not "ControllerTestA"), it serves the "/TestA/*" URL's. If you have a method TestA in there it will serve "/TestA/TestA".
If your method returns View(someModel) it will look for a view named TestA.cshtml/TestA.aspx, named like your method, within a folder Views\TestA (named like your controller, without the "Controller" suffix)
The view will render the HTML based on the someModel passed by the controller.
Within the view you may call other URL's or post data to some. This closes the circle.
As for the parameters or overloads, there are some restrictions:
You can define overloads for GET vs. POST vs. PUT vs. DELETE. You will need to annotate the methods with the according attributes though.
However you cannot define multiple overloads of the same method name for POSTs with different sets of parameters. You will need to make your POST method signature such that parameters can or cannot be sent to the server:
Example:
public ActionResult TestA(
string someOptionalParameter, int? someOtherOptionalParam)
{
if (string.IsNullOrEmpty(someOptionalParameter)) { ... }
if (someOtherOptionalParam == null) { ... }
}
The model-mapper will set your parameters to null if they are not posted to the server.
Like Khalid already mentioned - you should not mix up the concepts of MVC and WebForms. They are very different. MVC has no such thing as a "view state" which could be posted to the server. It has no WebForm-like lifecycle for the ASPX (or CSHTML) pages.
If you have a form in a view, then that form has a url to which it will post to. This URL is in the Html.BeginForm method in your view.
The form will then be posted to the appropriate controller methond in the approoriate controller
So if BeginForm starts like this:
using (Html.BeginForm("AddProduct", "Product"
Then the action method "AddProduct" in the controller Product (ProductController is the class name) will be called.
Like many people using ASP.NET MVC, I've implemented my own custom 404 error handling scheme using an approach similar to the one described here: How can I properly handle 404 in ASP.NET MVC?
(I actually discovered that post after implementing my own solution, but what I came up with is virtually identical.)
However, I ran into one issue I'm not sure how to properly handle. Here's what my 404 action in my ErrorController class looks like:
public ActionResult NotFound(string url)
{
url = (url ?? "");
if (Request.Url.OriginalString.Contains(url) &&
Request.Url.OriginalString != url)
{
url = Request.Url.OriginalString;
}
url = new Uri(url).AbsolutePath;
// Check URL to prevent 'retry loop'
if (url != "/Error/NotFound")
{
Response.StatusCode = (int)HttpStatusCode.NotFound;
// Log 404 error just in case something important really is
// missing from the web site...
Elmah.ErrorSignal.FromCurrentContext().Raise(
new HttpException(Response.StatusCode,
String.Format("Resource not found: {0}", url)));
}
return View();
}
The part that's different from the answer in the other StackOverflow question I referenced above is how the 'retry loop' is prevented. In other other answer, the code that prevents the retry loop simply sets properties on a ViewModel, which doesn't seem to actually prevent the loop. Since the action is sending back a response code of 404, then accessing the action directly (by typing "/Error/NotFound" in the browser) causes an infinite loop.
So here's my question: Did I miss another, more obvious way to handle the retry loop issue, or is my approach a decent way to do this?
you can handel erros by enabling the customErrors mode in the web.config file and set it to redirect errors to your controller when any errors occurs.
see an example here