MVC Routing many optional parameters

Question

I'm working on a site that will have the ability to filter a list of items based on user selection, much like you can filter the results of an amazon search. I'm not sure how to build a route that can accept many various parameters, of which none are required.

ideally, the final result would look something like:

1. mysite.com/dothings/filter1/sometext/filter5/sometext/filter11/sometext

or

2. mysite.com/dothings/filter1:sometext/filter5:sometext/filter11:sometext

for both of these, I don't understand how to set up the routes to handle random filters / random ordering of filters.

Currently my code is just:

//the real code would have 10+ filters
[Route("filter1/{filter1}/filter2/{filter2}")]
public IActionResult DoThings(string filter1 = null, string filter2 = null)
{
    return Ok("Test");
}

but even with the optional parameter, if I leave out filter1 it doesn't hit my action at all.

Is there a common approach to this type of requirement?

Answer 1

The reason it does not hit your action when you leave a filter out, is because you have the filters as part of the route.

If you have filter1 = null; filter2 = "foo" then this is the scenario:

• Expect: ../filter1/{filter1}/filter2/{filter2}
• Actual: ../filter1/filter2/foo

Instead you should use query parameters. Then the query will look like this:

mysite.com/dothings?filter1=sometext&filter5=sometext&filter11=sometext

And the route will look like:

[Route("DoThings")]
public IActionResult DoThings(string filter1 = null, string filter2 = null)
{
    return Ok("Test");
}

Also since you mentioned that this will have 10+ parameters I would suggest creating a class for the filters. For example:

public class MyFilters 
{
    public string filter1 { get; set; }
    public string filter2 { get; set; }
    ...
}

[Route("DoThings")]
public IActionResult DoThings(MyFilters filters)
{
    return Ok("Test");
}

Here are some related questions:

• Designing a REST api by URI vs query string
• REST API Best practices: Where to put parameters?

Answer 2

As @fqhv pointed out, your first choice should be to use query string parameters. They are not part of the route and therefore will match your path no matter what, and can be supplied in any combination and in any order. The only situation where that approach might not work is when you are trying to make user or search-engine friendly URLs.

Alternatively, you can make extension methods that dynamically build routes in order to achieve every permutation of route value combination.