Proper way to return JSON list in Web API with MVC and partial model

Question

I am trying to use Web API to grab certain fields from my MVC controller. I can't seem to match the right type with the right list. I am fine with converting everything to string.

I either get an error in code (can not convert types), or if I get it to compile, I get this error:

"The 'ObjectContent`1' type failed to serialize the response body for content type 'application/xml; charset=utf-8'."

From other similar posts, people responded with how to create a list, but not with the declaration of the return value of the Get. Please include both.

Also I would prefer not to add additional controllers as I need to do this on a number of my models.

Here is my code--note you can see I tried a number of different ways:

public class APICLIENTsController : ApiController
{
    private ApplicationDbContext db = new ApplicationDbContext();

    // GET api/<controller>
    public IEnumerable<string> Get()
    //public IEnumerable<CLIENT> Get()
    {
        //return db.CLIENTs.OrderBy(x => x.CLIENTNAME).ToList();
            string[] listOfUsers = db.CLIENTs.OrderBy(x => x.CLIENTNAME).Select(r => new
            {
                ID = r.CLIENTID.ToString(),
                NAME = r.CLIENTNAME
        });

        return listOfUsers.ToList();
        //return db.CLIENTs.Select(x => new { x.CLIENTNAME }).ToArray();
    }

You query is creating a collection of anonymous object (with 2 properties ID and NAME) not an array of string — user3559349
– user3559349, Commented Jun 24, 2016 at 23:11
So how do I fix? I am starting with an iqueryable model and i don't mind converting it to anything that I can pull out of this api. — Paul X
– Paul X, Commented Jun 24, 2016 at 23:15
Not clear what you really want to return. If you want to return a collection of objects, create a view model (say class Item with int ID and string Name) and use IEnumerable<Item> listOfUsers = db.CLIENTs.OrderBy)..).Select(r => new Item { ID = r.CLIENTID, Name = r,CLIENTNAME)}; return listOfUsers; and make the method public IEnumerable<Item> Get() — user3559349
– user3559349, Commented Jun 24, 2016 at 23:22
I have a number of these api calls to make so I don't want to create 20 view models. I just want the easiest way to get this out to Json. I am fine with converting everything to string if I could just do it in the function (but I don't know how). — Paul X
– Paul X, Commented Jun 24, 2016 at 23:29
I don't see how a string[] could possibly help you. How are you using this data? — user3559349
– user3559349, Commented Jun 24, 2016 at 23:32

Legends · Accepted Answer · 2016-06-24 21:13:44Z

3

If you want to return JSON use the

JsonResult

type.

public JsonResult Get()
{
    //return db.CLIENTs.OrderBy(x => x.CLIENTNAME).ToList();
    string[] listOfUsers = db.CLIENTs.OrderBy(x => x.CLIENTNAME).Select(r => new
    {
        ID = r.CLIENTID.ToString(),
        NAME = r.CLIENTNAME
    });

    return Json(listOfUsers.ToList(), JsonRequestBehavior.AllowGet);    
}

answered Jun 24, 2016 at 21:13

Legends

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2 Comments

Paul X Over a year ago

Thanks. This points me in the right direction, but... If I do string[] listOfUsers.., I get error: Error CS0029 Cannot implicitly convert type 'System.Linq.IQueryable<<anonymous type: string NAME>>' to 'string[]' If I change it to var listOfUsers... I get error: Error CS0029 Cannot implicitly convert type 'System.Web.Http.Results.JsonResult<System.Collections.Generic.List<<anonymous type: string NAME>>>' to 'System.Web.Mvc.JsonResult'

Alexander Over a year ago

How to make Get method here accept fromBody object and make it work via POST request?

Community · Accepted Answer · 2017-05-23 12:32:56Z

Your query is returning a collection of anonymous objects, not string[] so it will throw an exception. Even if you were to generate string[] by concatenating the CLIENTID and CLIENTNAME properties, it would be a little use to the client.

Create a model to represent what you need to return to the view

public class ClientVM
{
    public int ID { get; set; }
    public string Name { get; set; }
}

and modify your method to

public IEnumerable<ClientVM> Get()
{
    IEnumerable<ClientVM> model = db.CLIENTs.OrderBy(x => x.CLIENTNAME).Select(r => new ClientVM
    {
        ID = r.CLIENTID,
        Name = r.CLIENTNAME
    });
    return model;
}

Side note: depending on how your calling and consuming this in the client, you may need to change the Content-Type to specifically return json (refer these answers for more detail)

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