Build JSON response in Web API controller

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
}