Passing multiple or complex parameters to a GET handler

Question

User349337957 posted

I feel like I'm trying to do a really simple thing, but I can't figure out how to do it.  Basically, I have a Web API controller that I am using to query data using complex and arbitrary data.  For example, let's pretend my Controller is called YelpController and its intent is to allow the consumer to find restaurants.  I would want to do something like this:

// here's my search criteria; these are all optional
public class SearchCriteria 
{ 
     public int Latitude { get; set; } 
     public int Longitude { get; set; } 
     public string Cuisine { get; set; } 
     public ExpenseCategory { get; set; } 
}

public IEnumerable<Restaurant> GetByCriteria(SearchCriteria filters)
{
    // do stuff
    return matches;
}

I'd like to issue this via an ajax request, like this:

$.ajax(
{
    url: "/api/Yelp/GetByCriteria",
    type: "GET",
    contentType: "application/json",
    data: JSON.stringify({ Latitude: 47.6097, Longitude: -122.3331 }),
    success: function (result) {
        alert(result.Result);
    }
});

Clearly, this doesn't work since I can't send a "data" payload along with a GET request.  I could do this with a POST, but that seems hacky.

Instead of using one wrapper class as a single input parameter, I could split it out and have 4 parameters to the method and pass them in via a query string (eg /api/Yelp/GetByCriteria?latitude=xxx&longitude=yyy), but that is REALLY brittle and would require my API to change every time I add a new parameter.

Also, I clearly cannot use OData/IQueryable; my datastore is NoSQL and, besides, the parameters I want to pass aren't even supported currently.

So, what's the PROPER solution for this scenario?  This seems like a super common use case, but I can't find anyone else with the same problem

Answer 1

User401360897 posted

A custom filter will be help you here. You need to pass just a single json querystring in url,  for example,

?json={"Latitude"%3A+47.6097%2C+"Longitude"%3A+-122.3331}

Edit: you can improve this method by doing,

    public class BindJson : System.Web.Http.Filters.ActionFilterAttribute
    {
        Type _type;
        string _queryStringKey;
        public BindJson(Type type, string queryStringKey)
        {
            _type = type;
            _queryStringKey = queryStringKey;
        }
        public override void OnActionExecuting(System.Web.Http.Controllers.HttpActionContext actionContext)
        {
            var json = actionContext.Request.RequestUri.ParseQueryString()[_queryStringKey];
            var serializer = new JavaScriptSerializer();
            actionContext.ActionArguments[_queryStringKey] = serializer.Deserialize(json, _type);
        }
    }

    public class YelpController : ApiController
    {
        [BindJson(typeof(SearchCriteria), "json")]
        public IEnumerable<Restaurant> GetByCriteria(SearchCriteria json)
        {
            

            // do stuff
            return new List<Restaurant>();
        }

    }

You can construct this with JSON.stringify method. Here is a possible filter,

    public class BindJson : System.Web.Http.Filters.ActionFilterAttribute
    {
        public override void OnActionExecuting(System.Web.Http.Controllers.HttpActionContext actionContext)
        {
            var json = actionContext.Request.RequestUri.ParseQueryString()["json"];
            var serializer = new JavaScriptSerializer();
            actionContext.ActionArguments["filters"] = serializer.Deserialize(json, typeof(SearchCriteria));
        }
    }

    public class YelpController : ApiController
    {
        [BindJson]
        public IEnumerable<Restaurant> GetByCriteria(SearchCriteria filters)
        {
            

            // do stuff
            return new List<Restaurant>();
        }

    }

Answer 2

User349337957 posted

Excellent.  Passing URL encoded stringified JSON in a query string is probably not the most elegant solution, but so far it seems to work.  Thanks!

Answer 3

User-356739632 posted

Hi Thanks for the solution

Answer 4

User1115704286 posted

Interesting question. I have the same dilemma - what's the best way to pass a json query object as a parameter.

However, cramming it in the URL doesn't seem quite right to me - isn't it better to just POST the thing, and return the result in the response body? That's also a bit non-standard as the response bodies of POST requests are not usually used to transfer data but as far as I'm aware it's supported.

Answer 5

User-1588480722 posted

Instead of using one wrapper class as a single input parameter, I could split it out and have 4 parameters to the method and pass them in via a query string (eg /api/Yelp/GetByCriteria?latitude=xxx&longitude=yyy), but that is REALLY brittle and would require my API to change every time I add a new parameter.

What is wrong with this? As I see, this is the CORRECT way to do. It is not brittle. Let me guess why you think it is brittle - you are assuming that you need to have multiple input parameters in the web api method. No!!! You can maintain the same complex object as the input parameter and add [FromUri] attributes to each of the members.