MVC query string with ICollection or array

Question

My MVC 4 web service has a new use case. I need to pass a list of arguments on the query string to a Web API, e.g.,

http://host/SomeWebApi?arg=x&arg=y

I previously did this simply and easily in my Web Site controller using ICollection<string> arg as a parameter in the controller. That is working now, but it is a Web page, as opposed to an API.

Now I am knocking my head against the wall trying to get a Web API version of the same thing to work. I've made a simple test interface, below, and the collection arg is always null. I've tried List<string> and string[] as types as well. What am I overlooking?

Route register:

config.Routes.MapHttpRoute(
    name: "Experiment",
    routeTemplate: "Args",
    defaults: new
    {
        controller = "Storage",
        action = "GetArgTest",
        suite = UrlParameter.Optional,
    },
    constraints: new
    {
        httpMethod = new HttpMethodConstraint(new HttpMethod[] { new HttpMethod("GET") })
    }
);

Web API controller code:

public string GetArgTest(ICollection<string> suite)
{
    if (suite == null)
    {
        return "suite is NULL";
    }
    else
    {
        return "suite is NON-NULL";
    }
}

Test query string that results in "suite is NULL":

http://localhost:5101/Args?suite=1&suite=2

If I use GetArgTest(string suite), then I get a non-NULL value, but the text says "(Collection)". Super frustrating. — jws
– jws, Commented May 23, 2013 at 15:29
Sadly, I timed out on this issue, and resorted to: List<string> suite = new List<string>(); IEnumerable<KeyValuePair<string, string>> queryPairs = Request.GetQueryNameValuePairs(); foreach (var pair in queryPairs) { if (pair.Key == "suite") { suite.Add(pair.Value); } } — jws
– jws, Commented May 23, 2013 at 18:08

Community · Accepted Answer · 2017-05-23 12:23:12Z

2

I came across this answer ApiController Action Failing to parse array from querystring and discovered that to resolve this you need to put in the FromUriAttribute. So in your example:

public string GetArgTest([FromUri]ICollection<string> suite)
{
}

This makes sense I guess, typically with an API controller you'd expect to be doing more POST and PUT requests for which you'd typically include post data rather than a QueryString.

edited May 23, 2017 at 12:23

CommunityBot

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answered Oct 13, 2014 at 10:10

Ian

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