I'm looking for a way to share data between HtmlHelpers. The goal is to set configuration once instead of passing a parameter with each call. In the example below, I'm setting the form type to determine the grid configuration:
#{ Html.SetFormType(HtmlHelpers.FormType.Boxed); }
#Html.FormItemFor(m => m.LoginName)
#Html.FormItemFor(m => m.Password)
public static void SetFormType(this HtmlHelper helper, FormType formType)
{
helper.ViewBag.FormType = formType;
helper.ViewContext.ViewBag.FormType = formType;
}
Setting ViewBag does not persist through subsequent #Html calls. Setting ViewContext.ViewBag persists, but is it safe to do so?
The existing method EnableUnobtrusiveJavaScript is set in an instance of the ScopeCache class, which in turn is added to HttpContext.Items. Perhaps that's also a candidate to store my data?
You can use the request-based-scope object of HttpContext.Current.Items because HttpContext.Current is actually the only container that is unique and always there in a request.
Cheers
PS: don't put everything directly into the items. Just add a controller-item there and work on this.
Related
This is an example of what I want to achieve, however I want to do my own custom attribute that also feeds itself from something other than the request url. In the case of HttpGet/HttpPost these built-in attributes obviously have to look at the http request method, but is there truly no way to make Url.Action() resolve the correct url then?
[HttpGet("mygeturl")]
[HttpPost("myposturl")]
public ActionResult IndexAsync()
{
// correct result: I get '/mygeturl' back
var getUrl = Url.Action("Index");
// wrong result: It adds a ?method=POST query param instead of returning '/myposturl'
var postUrl = Url.Action("Index", new { method = "POST" });
return View();
}
I've looked at the aspnet core source code and I truly can't find a feature that would work here. All the LinkGenerator source code seems to require routedata values but routedata always seems to require to be in the url somewhere, either in the path or in the query string. But even if I add the routedata value programmatically, it won't be in time for the action selection or the linkgenerator doesn't care.
In theory what I need is to pass something to the UrlHelper/LinkGenerator and have it understand that I want the url back out that I defined in my custom attribute, in this case the HttpPost (but I'll make my own attribute).
In ASP.Net Core you have multiple ways to generate an URL for controller action, the newest being tag helpers.
Using tag-helpers for GET-requests asp-route is used to specify route parameters. It is from what I understand not supported to use complex objects in route request. And sometimes a page could have many different links pointing to itself, possible with minor addition to the URL for each link.
To me it seems wrong that any modification to controller action signature requires changing all tag-helpers using that action. I.e. if one adds string query to controller, one must add query to model and add asp-route-query="#Model.Query" 20 different places spread across cshtml-files. Using this approach is setting the code up for future bugs.
Is there a more elegant way of handling this? For example some way of having a Request object? (I.e. request object from controller can be put into Model and fed back into action URL.)
In my other answer I found a way to provide request object through Model.
From the SO article #tseng provided I found a smaller solution. This one does not use a request object in Model, but retains all route parameters unless explicitly overridden. It won't allow you to specify route through an request object, which is most often not what you want anyway. But it solved problem in OP.
<a asp-controller="Test" asp-action="HelloWorld" asp-all-route-data="#Context.GetQueryParameters()" asp-route-somestring="optional override">Link</a>
This requires an extension method to convert query parameters into a dictionary.
public static Dictionary GetQueryParameters(this HttpContext context)
{
return context.Request.Query.ToDictionary(d => d.Key, d => d.Value.ToString());
}
There's a rationale here that I don't think you're getting. GET requests are intentionally simplistic. They are supposed to describe a specific resource. They do no have bodies, because you're not supposed to be passing complex data objects in the first place. That's not how the HTTP protocol is designed.
Additionally, query string params should generally be optional. If some bit of data is required in order to identify the resource, it should be part of the main URI (i.e. the path). As such, neglecting to add something like a query param, should simply result in the full data set being returned instead of some subset defined by the query. Or in the case of something like a search page, it generally will result in a form being presented to the user to collect the query. In other words, you action should account for that param being missing and handle that situation accordingly.
Long and short, no, there is no way "elegant" way to handle this, I suppose, but the reason for that is that there doesn't need to be. If you're designing your routes and actions correctly, it's generally not an issue.
To solve this I'd like to have a request object used as route parameters for anchor TagHelper. This means that all route links are defined in only one location, not throughout solution. Changes made to request object model automatically propagates to URL for <a asp-action>-tags.
The benefit of this is reducing number of places in the code we need to change when changing method signature for a controller action. We localize change to model and action only.
I thought writing a tag-helper for a custom asp-object-route could help. I looked into chaining Taghelpers so mine could run before AnchorTagHelper, but that does not work. Creating instance and nesting them requires me to hardcode all properties of ASP.Net Cores AnchorTagHelper, which may require maintenance in the future. Also considered using a custom method with UrlHelper to build URL, but then TagHelper would not work.
The solution I landed on is to use asp-all-route-data as suggested by #kirk-larkin along with an extension method for serializing to Dictionary. Any asp-all-route-* will override values in asp-all-route-data.
<a asp-controller="Test" asp-action="HelloWorld" asp-all-route-data="#Model.RouteParameters.ToDictionary()" asp-route-somestring="optional override">Link</a>
ASP.Net Core can deserialize complex objects (including lists and child objects).
public IActionResult HelloWorld(HelloWorldRequest request) { }
In the request object (when used) would typically have only a few simple properties. But I thought it would be nice if it supported child objects as well. Serializing object into a Dictionary is usually done using reflection, which can be slow. I figured Newtonsoft.Json would be more optimized than writing simple reflection code myself, and found this implementation ready to go:
public static class ExtensionMethods
{
public static IDictionary ToDictionary(this object metaToken)
{
// From https://geeklearning.io/serialize-an-object-to-an-url-encoded-string-in-csharp/
if (metaToken == null)
{
return null;
}
JToken token = metaToken as JToken;
if (token == null)
{
return ToDictionary(JObject.FromObject(metaToken));
}
if (token.HasValues)
{
var contentData = new Dictionary();
foreach (var child in token.Children().ToList())
{
var childContent = child.ToDictionary();
if (childContent != null)
{
contentData = contentData.Concat(childContent)
.ToDictionary(k => k.Key, v => v.Value);
}
}
return contentData;
}
var jValue = token as JValue;
if (jValue?.Value == null)
{
return null;
}
var value = jValue?.Type == JTokenType.Date ?
jValue?.ToString("o", CultureInfo.InvariantCulture) :
jValue?.ToString(CultureInfo.InvariantCulture);
return new Dictionary { { token.Path, value } };
}
}
I have a Website that contains a number of webpages and some WCF services.
I have a logging IHttpModule which subscribes to PreRequestHandlerExecute and sets a number of log4net MDC variables such as:
MDC.Set("path", HttpContext.Current.Request.Path);
string ip = HttpContext.Current.Request.ServerVariables["HTTP_X_FORWARDED_FOR"];
if(string.IsNullOrWhiteSpace(ip))
ip = HttpContext.Current.Request.ServerVariables["REMOTE_ADDR"];
MDC.Set("ip", ip);
This module works well for my aspx pages.
To enable the module to work with WCF I have set aspNetCompatibilityEnabled="true" in the web.config and RequirementsMode = AspNetCompatibilityRequirementsMode.Allowed on the service.
But when the service method is called the MDC no longer contains any of the set values. I have confirmed they are being set by putting a logging method in the PreRequestHandlerExecute.
I think the MDC is loosing the values because in the log I can see the PreRequestHandlerExecute handler method and service method calls are on separate
threads.
The post log4net using ThreadContext.Properties in wcf PerSession service suggests using log4net.GlobalContext but I think that solution would run into issues if two users hit the application at the same time as GlobalContext is shared by all threads.
Is there a way to make this work?
Rather than taking the values from the HttpContext and storing them in one of log4net's context objects, why not log the values directly from the HttpContext? See my answer to the linked question for some techniques that might work for you.
Capture username with log4net
If you go to the bottom of my answer, you will find what might be the best solution. Write an HttpContext value provider object that you can put in log4net's GlobalDiagnosticContext.
For example, you might do something like this (untested)
public class HttpContextValueProvider
{
private string name;
public HttpContextValueProvider(string name)
{
this.name = name.ToLower();
}
public override string ToString()
{
if (HttpContext.Current == null) return "";
var context = HttpContext.Current;
switch (name)
{
case "path":
return context.Request.Path;
case "user"
if (context.User != null && context.User.Identity.IsAuthenticated)
return context.User.Identity.Name;
case "ip":
string ip = context.Request.ServerVariables["HTTP_X_FORWARDED_FOR"];
if(string.IsNullOrWhiteSpace(ip))
ip = context.Request.ServerVariables["REMOTE_ADDR"];
return ip;
default:
return context.Items[name];
}
return "";
}
}
In the default clause I assume the name, if it is not a specifically case that we want to handle, represents a value in the HttpContext.Current.Items dictionary. You could make it more generic by also adding the ability to access Request.ServerVariables and/or other HttpContext information.
You would use this object like so:
Somewhere in your program/web site/service, add some instances of the object to log4net's global dictionary. When log4net resolves the value from the dictionary, it will call ToString before logging the value.
GDC.Set("path", new HttpContextValueProvider("path"));
GDC.Set("ip", new HttpContextValueProvider("ip"));
Note, you are using log4net's global dictionary, but the objects that you are putting in the dictionary are essentially wrappers around the HttpContext.Current object, so you will always be getting the information for the current request, even if you are handling simultaneous requests.
Good luck!
I've got a Manage User event that takes an an optional userID and displays a user edit screen. There is a manageUserViewModel to go with this screen.
My Manage page has some dependencies - eg, PageTitle, what method to submit to, etc.
If I validate-fail, I need to show the manage screen again, but this time, using the view-model that was passed into the same method.
Supplying these dependencies in the fail scenario isn't very DRY.
How do I step repeating the dependencies? I tried putting them into a separate method, but that does not feel right.
public ActionResult Manage(Guid? UserID)
{
User user = this._UserLogic.GetUser(UserID);
ViewBag.Title = "User List";
ViewBag.OnSubmit = "Save";
ManageUserViewModel uvm = Mapper.Map<User, ManageUserViewModel>(user);
return View("Manage", uvm);
}
[AcceptVerbs("POST")]
public ActionResult Save(ManageUserViewModel uvm)
{
User user = this._UserLogic.GetUser(uvm.UserID);
if (!ModelState.IsValid)
// This is not very DRY!!!
ViewBag.Title = "Manage User";
ViewBag.OnSubmit = "Save";
return View("Manage", uvm);
}
Mapper.Map<ManageUserViewModel, User>(uvm, user );
this._UserLogic.SaveUser(user);
return RedirectToAction("Manage", new { UserID = user.ID });
}
I think you misunderstand DRY. DRY does not mean "NEVER repeat yourself", it means that you should not repeat yourself when it makes sense not to.
Different views have different requirements, and creating a complex structure just to avoid repeating yourself violates other best practices, like KISS, and SRP.
SOLID is interesting because Single Responsibility Principle is often at odds with Don't Repeat Yourself, and you have to come up with a balance. In most cases, DRY loses because SRP is far more important.
It looks to me like you have code here that is handling multiple responsibilities just so you can avoid writing similar code more than once. I disagree with doing that, because each view has different responsibilities and different requirements.
I would suggest just creating separate controller actions, views, and models for each action, particularly if the validation requirements are different for them. There may be a few things you can do (like using Partial Views or Editor Templates) to reduce repetition, but in general don't add lots of complexity just to avoid repetition.
You could add the 'Manager User' Title and 'Save' OnSubmit strings as properties of on the ManageUserViewModel. This means that you would not have to add them to the ViewBag each time you called Save.
You could also make a ManageUserService which could be responsible for the AutoMapper mappings and saving the user.
You code would then look like this:
public ActionResult Manage(Guid? UserID)
{
var uvm = _userService.GetById(UserId);
return View("Manage", uvm);
}
[AcceptVerbs("POST")]
public ActionResult Save(ManageUserViewModel uvm)
{
if (!ModelState.IsValid)
{
return View("Save", uvm);
}
_userService.Save(uvm);
return RedirectToAction("Manage", new { UserID = uvm.ID });
}
Just put the CRUD logic and AutoMapping functionality in the a class called UserService, and instance of which can be injected using Inversion of Control into your controller.
If you don't want to hard-code your string values into the view model itself, then you could add the values to an ApplicationResources file and reference those from the view model.
You will have to find some way to preserve this information between requests, which either means passing it back and forth between the client and server or saving it on the server. Saving it on the server means something like session but this feels a little heavy to me. You could add it to your ViewModel as #Ryan Spears suggested. To me that feels a little wrong, polluting the ViewModel with something that might be considered metadata. But that is just an opinion and I am not discrediting his answer because it is valid. Another possibility would be to just add the extra fields to the parameter list of the action method itself and use hidden fields.
[AcceptVerbs("POST")]
public ActionResult Save(ManageUserViewModel uvm, string title, string onSubmit)
{
...
}
In the form add:
<input type="hidden" name="title" value="#ViewBag.Title" />
<input type="hidden" name="onSubmit" value="#ViewBag.OnSubmit" />
This is essentially the same concept and solution as adding them to the ViewModel except in this situation they are not actually part of the ViewModel.
You can use RedirectToAction() and then export and import your tempdata (to maintain the ModelState) if you're worried about the 3 lines.
Personally I'd find it a lot more readable if you kept the logic in the POST version of the method, as you're performing something slightly different from the GET method, therefore not really repeating yourself. You could you probably keep the two ViewBag variables you have inside the View, and then there's no repetition at all.
As a side note: [HttpPost] now supersedes [AcceptVerbs]
We have come up with another solution that I thought I would share.
This based on the view-model containing info on what actions it can do, but we feel the controller should be specifying these (ie, controlling what actions different links route to) these because we have cases where the view-models are reused across actions. EG, the case where when you edit you can edit a template or an instance of something - the UI is the same, the only difference is the actions you post to/cancel from.
We abstracted away the part of the view-model that contains the data bound properties and the view model that contains other things we need for the view to render. We call the property-only object a DTO - it's not a true dto because it contains validation attributes.
We figure that we might be able to re-use these DTO's in the future for ajax or even XML requests - it, can keep validation DRY.
Anyway - here is an example of the code, we are happy with it (for now) and hope it helps others.
[HttpGet]
[ValidateInput(false)]
public virtual ActionResult ManageUser(ManageUserDTO dto, bool PopulateFromObject = true)
{
User user = this._UserLogic.GetUser(dto.UserID);
if (PopulateFromObject)
Mapper.Map<User, ManageUserDTO>(user, dto);
ManageUserViewModel vm = new ManageUserViewModel()
{
DTO = dto,
PageTitle = Captions.GetCaption("pageTitle_EditUser"),
OnSubmit = GetSubmitEventData(this.ControllerName, "SaveUser"),
OnCancel = GetCancelEventData(this.ControllerName, "ListUsers"),
};
return View("ManageUser", vm);
}
[HttpPost]
public virtual ActionResult SaveUser(ManageUserViewModel vm)
{
User user = this._UserLogic.GetUser(vm.DTO.UserID);
if (!ModelState.IsValid)
{
return ManageUser(vm.DTO, false);
}
Mapper.Map<ManageUserDTO, User>(vm.DTO, user);
this._UserLogic.SaveUser(user);
TempData.AddSuccess(Captions.GetCaption("message_UserSavedSuccessfuly"));
return RedirectToAction("ManageUser", new { UserID = user.ID });
}
The model-binder will set any URI variables into the dto in the get action. My logic layer will return a new User object if a call to getUserByID(null) is made.
I'm trying to use a single controller to list multiple similar collections so I can call different templates with the same controller. In fact, right now I have 6 controllers for listing and another 6 for forms but they're all duplicates.
I've made a non-functional plunker just to show how I intend it to work. I've avoided declaring routeProviders because knowing it wouldn't work I tried to make it as straight to the point as I could.
http://plnkr.co/edit/d06PcrJS5newhrmNy6EJ?p=preview
I've seen on stackoverflow how to declare a class with a dynamic name:
var str = "MyClass";
var obj = new window[str];
But as I have not been able to find where it's stored I'm not able to retrieve it.
Does anyone have a hint on how to do this?
You can use Angular's injector to return the service instance you want. For example:
app.controller('NodeListCtrl', function($scope, $location, $injector) {
var modelName = $location.path().split("/")[1];
$scope.modelName = modelName.charAt(0).toUpperCase() + modelName.slice(1);
$scope.nodes = $injector.get($scope.modelName).query();
});
Note: Don't forget to add the $injector to the controller's function signature.
jsfiddle: http://jsfiddle.net/bmleite/Mvk2y/