Build JSON response in Web API controller

Question

In a WebAPI project, i have a controller that checks a status of a product, based on a value the user enters.

Lets say they enter "123" and the response should be "status": 1, AND a list of products. If they enter "321" the "status" is 0, AND a list of products.

My question is, how do i build such a string correct in a WebAPI controller.

[Route("{value:int}")]
public string GetProducts(int value)
{
    var json = "";
    var products = db.Products;
    if (products.Any())
    {
        foreach (var s in products)
        {
            ProductApi product = new ProductApi();
            product.Name = s.Name;
            json += JsonConvert.SerializeObject(supplier);
        }
    }

    var status = db.Status;
    if (status.Any())
    {
        json += "{status:1}";
    }
    else
    {
        json += "{status:0}";
    }

    return json;
}

public class ProductApi
{
    public string Name { get; set; }
}

Also, is this output/response considered valid?

[
    {
        "id":1,
        "name":"product name"
    },
    {
        "id":2,
        "name":"product name 2"
    },
    {
        "id":3,
        "name":"product name 3"
    }
]

{
    "status": 0
}

You should not create json by your own, you can return an object from this method and make JSON as default format for returned data. — Red
– Red, Commented Mar 11, 2016 at 10:02
JObect is also a great tool: newtonsoft.com/json/help/html/CreatingLINQtoJSON.htm — yu yang Jian
– yu yang Jian, Commented May 21, 2018 at 5:59
Possible duplicate of How to change default Web API 2 to JSON formatter? — Liam
– Liam, Commented Jun 19, 2018 at 12:56

Red · Accepted Answer · 2017-02-28 11:01:37Z

So here are the changes for your post:

First, you should make your api return Json by default when you pass a text/html request (is this you are looking for?), adding this line to your WebApiConfig class:

config.Formatters.JsonFormatter.SupportedMediaTypes.Add(new MediaTypeHeaderValue("text/html"));

Second, I changed the code to return a real object, impersonating your response:

public class ProductApiCollection
{   
    public ProductApi[] Products { get; set; }      
    public byte Status { get; set; }
}

public class ProductApi
{
    public string Name { get; set; }
}

Method body:

public ProductApiCollection Get()
{
    var result = new ProductApiCollection();
    var dbProducts = db.Products;
    var apiModels = dbProducts.Select(x => new ProductApi { Name = x.Name } ).ToArray();
    result.Products = apiModels;

    var status = db.Status.Any() ? 1 : 0;
    result.Status = status;

    return result;
}

This will results in the following example json:

{
  "Products": [
    {
      "Name": "Pork"
    },
    {
      "Name": "Beef"
    },
    {
      "Name": "Chicken"
    },
    {
      "Name": "Salad"
    }
  ],
  "Status": 1
}

I strongly advise you not to do manual formatting for such things, and rely on built-in and 3rd party libraries. Otherwise, you will be reinventing the things already available, tested and ready to work.

Seems like what i am looking fore. Just one question though: How do i iterate through db.Products to add them, instead of the manual "new ProductApi" in your example? I need to wrap the new ProductApi in a ForEach basicly?
@brother, I updated the answer with simple sample code using db, please take a look. Also consider that if you have a lot of products, this method will be very slow, so paging is a good thing to consider from the start.
Remember you can take advantage of anonymous types in any scenario where you are selecting data to be returned as JSON

Tamas Ionut · Accepted Answer · 2017-05-22 15:57:52Z

4

Just as raderick mentioned, you don't need to create your own custom JSON infrastructure.

public class ProductApi
{
    public int Id {get;set;}
    public string Name { get; set; }
}

public class ResponseDTO
{
    public int Status {get;set;}
    public List<ProductApi> { get; set; }
}

And in your API action, return like this:

[Route("{value:int}")]
public ResponseDTO GetProducts(int value)
{
    ResponseDTO result = ...// construct response here 

    return result;
}

edited May 22, 2017 at 15:57

answered Mar 11, 2016 at 10:16

Tamas Ionut

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2 Comments

Leandro Bardelli Over a year ago

This is for MVC, not API

Leandro Bardelli Over a year ago

no problem, please take in consideration edit your answer in order to response the OP question and then get my upvote :)

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