I was wondering whether there is a way to create an ActionLink or similar, that changes only a few parameters of the actual query, and keeps all the other parameters intact. For example if I'm on an URL like http://example.com/Posts/Index?Page=5&OrderBy=Name&OrderDesc=True I want to change only the Page, or OrderBy parameter and keep all other parameters the same, even those I don't yet know of (like when I want to add a Search parameter or something similar too).
The header of my current action looks like this:
public ActionResult Index(int? Page, string OrderBy, bool? Desc)
and I'm only interested in the values that this controller "eats". I want however that when I extend this action (for example with a string Search parameter) the links should work the same way as before.
Here is what I did already:
Create a new RouteValueDictionary and fill it with everything from RouteData.Values
Problem: This only fills the parameters that are used in the Routing, so all other optional parameters (like Page) to the controller are lost
Add everything from HttpContext.Request.QueryString to the previous dictionary
This is what I am currently using
Problem: It might have some junk stuff, that the Controller didn`t ask for, and it doesn't work if the page was loaded using POST. You also don't have any ModelBindings (but this isn't much of a problem, because we are re-sending everything anyway)
Use HttpContext.Request.Params
Problem: this has too much junk data which imho one shouldn't add to a RouteValueDictionary that is passed to an ActionLink
So the questions:
Is there an RVD that has all the data that was passed to the Controller and was used by it?
Is this solution good, or are there any caveats I didn't think about (mainly in the context of changing a few query parameters while keeping the others intact)?
Is there a way to filter out the "junk" data from the Params object?
EDIT: Checked the RouteData.DataTokens variable, but it's usually empty, and doesn't contain everything I need. It seems to only contain parameters that are needed for the routing somewhere, but not all of the parameters.
Have a look in RouteData.DataTokens.
RouteData.DataTokens # MSDN documentation:
Gets a collection of custom values that are passed to the route handler but are not used when ASP.NET routing determines whether the route matches a request.
HTHs,
Charles
Related
I'm pretty new to web development and swagger in general so apologies if the question is too naive.
I'll use the Asp.Net Core Web Api template in visual studio 2019 to better explain my problem, so please consider that environment in the case I have omitted some information (or just ask for the missing part that I'll bring it).
There we have the WeatherForecastController class with a simple GET (which I included the names parameter):
[HttpGet]
public IEnumerable<WeatherForecast> Get(IEnumerable<string> names)
{
//...
}
When I try to test this request using the Swagger page, it doesn't recognize the name parameter.
I have ran other tests to find out what's going on and I found the following:
Swagger does work with IEnumerable as it works pretty well if the parameter is of type IEnumerable<IFormFile> (it displays a list of uploaded files, shows the file selection dialog, etc);
I tried encapsulating the parameter(s) in a DTO class and it seems to break even more stuff (even the IEnumerable<IFormFile> doesn't seem to work inside a DTO class; it only works if passed directly in the parameter list of the [HttpVerb] method;
I tried with other similar types as well as ICollection<string>, List<string>, string[]; none of them seem to work;
This same problem happens using primitive types like bool, int, etc as type arguments to IEnumerable<T>;
So what is happening? Should I set some sort of configuration value so it can work with collections of primitive types?
Update with images showing the problem:
... Get(string names, IEnumerable<IFormFile> file):
... Get(IEnumerable<string> names, IFormFile file):
As you can see, when any parameter in the param list is of IEnumerable the swagger UI doesn't properly show the requested fields like in the second image.
You must specify model binding sources in your case. Your action method should be like this:
[HttpPost("test/names")]
public IEnumerable<string> PostNames([FromQuery]IEnumerable<string> names, IEnumerable<IFormFile> files)
{
//...some code
return names;
}
You shouldn't use two or more complex type parameter as an action parameters until you specify the source they are binding from. That's because complex objects are bound to request body by default and only one parameter can be bound to request body.
As of microsoft docs :
Don't apply [FromBody] to more than one parameter per action method. Once the request stream is read by an input formatter, it's no longer available to be read again for binding other [FromBody] parameters.
Complex type means class variables, arrays, and those which are not primary types like int,double, string and etc.
Swagger generates this UI for action above:
As the final word , Note that you can't send something in your request body when you are using GET http request.
Currently I have the following standard functions in each of my controllers to handle basic CRUD operations:
GET /api/todo Get all to-do items
GET /api/todo/{id} Get an item by ID
POST /api/todo Add a new item
PUT /api/todo/{id} Update an existing item
DELETE /api/todo/{id} Delete an item
However, the time came where I realized I actually need to pass multiple parameters to get a list of todo items that is filtered at the database level rather than retrieving all of the items and using linq.
For example here is how I decided to go about it:
In my Controller:
// POST: api/todo
[HttpPost]
public IList<TodoItem> Get([FromBody]GetTodoItemsRequest request)
{
return _todoItemManager.GetTodoItems(request.Name, request.CategoryId);
}
As you can see I created a new Model called GetTodoItemsRequest which will have a property for each of my parameters. In this case: Name, CategoryId.
I figured when dealing with multiple parameters and retrieving a list it is best to do POST and create a model specifically for it. Rather than using a GET and passing all kinds of information in the url.
It seems a bit strange to be doing the above... Would msot see it as a perfectly fine solution or is there something I am missing in the WebAPI world?
I believe that is semantically incorrect to use POST method for a simple read operation, even if you need a complex model. You are doing a pure query on your resource called todo, and this should really be a GET operation for many reasons:
It should be cachable: POST request aren't cachable by their nature, and caching is an important constraint in RESTful services.
It should semantically indicate that no side-effect will be raised from the call: GET requests must be idempotent and safe, POST operations, instead, indicate some kind of data manipulation. Your operation (filtering) is both idempotent and safe, so it should be spontaneously represented by a GET request.
The part of the URI after a ? character is called query string for a reason: it represent parameters that further specify the scope of a request. Well, isn't filtering results just an example of this approach?
Apart from that, it seems to me that, if Name and CategoryId are required parameters for your query, your filtering operation could be better represented by another URI in which Name and CategoryId are turned into route parameters:
http://yourhost.com/api/users/{name}/categories/{categoryId}/todos
Assuming a relationship between your name parameter (a user name maybe?) and the categories.
If, instead, your parameters are completely optional, then leaving them as query string parameters is the best choice:
http://yourhost.com/api/todos?name=nameValue&categoryId=categoryIdValue
A side note:
you should really use plural for your resources if they represents a collection of items: e.g. api/todo will return an array of todos, so you should rename it into api/todos.
I am currently on the page /Customer/Edit/13244.
When I use #Url.Action("Edit", "Customer") on the same page it returns me /Customer/Edit/13244, but I want it to return /Customer/Edit/.
Kindly tell me how to fix this issue.
This is a "feature" of MVC that many people find unnatural and was previously reported as a bug.
Microsoft's official response:
Ultimately if you want the most control over what gets generated for a URL there are a few options to consider:
Use named routes to ensure that only the route you want will get used to generate the URL (this is often a good practice, though it won't help in this particular scenario)
Specify all route parameters explicitly - even the values that you want to be empty. That is one way to solve this particular problem.
Instead of using Routing to generate the URLs, you can use Razor's ~/ syntax or call Url.Content("~/someurl") to ensure that no extra (or unexpected) processing will happen to the URL you're trying to generate.
Actually, this bug only rears its ugly head when you try to re-purpose an action method name. If you use a different action method name other than Edit in the case where it is not followed by id, this problem will magically disappear.
You will need to use (assuming your using the default route with id = UrlParameter.Optional
#Url.Action("Edit", "Customer", new { id = "" })
I'm currently in the process of designing as RESTful of an API as I can using Microsoft's Web API 2 in C#. What I'm struggling on is how best to represent resources or the proper way to do it where the GET call and POST/PUT are very different.
For example say I have something calls states that have an id, name, status, etc., these can be assigned to a document. So I have a route like this /documents/{id}/states/ . If I call a GET here I need to get the full list of all assigned states including their id, name, etc.
However, in order to change which states are assigned to the document I simply need to pass the id. I cannot do this individually, it must be an array that gets sent up since users may be interacting with hundreds or thousands at a time.
So in this case I have a few issues. I don't even know if POST or PUT is correct here, and second whichever one it is can I just take in an array of integers?
In your case, I would suggest PUT is the method you would be wanting to use, as you know the location of the resource that you are updating. For more info, see here: http://restcookbook.com/HTTP%20Methods/put-vs-post/
In ASP.NET Web API 2 you can use the [FromBody] parameter attribute, so that your method signature would be:
public void UpdateStates(int id, [FromBody]List<int> states) {}
More info on parameter attributes can be found here: http://www.asp.net/web-api/overview/formats-and-model-binding/parameter-binding-in-aspnet-web-api
This is the code I currently use:
<% Uri MyUrl = Request.UrlReferrer;
if( MyUrl != null)
Response.Write("Back"); %>
I would think there is a more "MVC Html helper" way to do a "Back" button. This may require more information about the routes already setup, a list of possible parameters, etc. but I don't want to assume this is the case. Maybe there is some way to match the url to the defined routes like in the manner a regular expression works?
What about adding the data you want to TempData, in an actionfilter or base controller class).
Each time when a page executes, it will add its info to the TempData, and the next page will know what the referrer was.The back button itself will be an HtmlHelper, that will simply go and fetch the data from the TempData.
This way you also eliminate the problem that some users don't send referrer info in the request.
well, for one you could always do what you did above, but inside a HtmlHelper.
As you pointed out, there's really too many variables to doing it based on routing, unless you havea known workflow (e.g. for a wizard).
I would suggest making it part of the view model, populated in your action. You could continue to use the referrer to populate it, or you could even have a "back url" parameter on your action, so that the calling page could supply its own back url.