WebApi Put "The parameters dictionary contains a null entry for parameter..."

Question

public class ContactsController : ApiController
{
    private static readonly List<Contact> _contacts = new List<Contact>();
    public Contact PutContacts(int id, Contact contact)
    {
        if (_contacts.Any(c => c.Id == contact.Id) == false)
        {
            throw new HttpResponseException(HttpStatusCode.NotFound);
        }
        contact.LastModified = DateTime.Now;
        return contact;
    }
}

http put header:

PUT /api/contacts/3 HTTP/1.1
User-Agent: Fiddler
Content-Type: application/json
Host: localhost:8080

body:

{"Id":3,"Name":"mmm","Phone":"000 000 0000","Email":"[email protected]","LastModified":"2012-03-08T23:42:13.8681395+08:00"}

response:

HTTP/1.1 400 Bad Request
"The parameters dictionary contains a null entry for parameter 'id' of non-nullable type 'System.Int32' for method 'SelfHost.Contact PutContacts(Int32, SelfHost.Contact)' in 'SelfHost.ContactsController'. An optional parameter must be a reference type, a nullable type, or be declared as an optional parameter."

Why? thanks.

PS:

config.Routes.MapHttpRoute(
            name: "DefaultApi",
            routeTemplate: "api/{controller}/{id}",
            defaults: new { id = RouteParameter.Optional }
        );

Answer 1

I am having this same issue. The query parameter, "id" is null and the object "contact" is filled in. I think this is a model binding issue. If you put a break point in the controller, look at this expression:

this.ControllerContext.RouteData.Values["id"]

You will see that the value is there in the route data; its just not getting set on the model. I have an ActionFilter and if I put a break point in there as well, I see that the actionContext's ActionArgument has a key for it, but a null value.

Im still researching...

Answer 2

I am unable to reproduce the issue you are describing.

Model:

public class Contact
{
    public int Id { get; set; }
    public string Name { get; set; }
    public string Phone { get; set; }
    public string Email { get; set; }
    public DateTime LastModified { get; set; }
}

Controller:

public class ContactsController : ApiController
{
    public Contact Put(int id, Contact contact)
    {
        return contact;
    }
}

Client:

class Program
{
    static void Main()
    {
        using (var client = new WebClient())
        {
            client.Headers[HttpRequestHeader.ContentType] = "application/json";
            var data = Encoding.UTF8.GetBytes(@"{""Id"":3,""Name"":""mmm"",""Phone"":""000 000 0000"",""Email"":""[email protected]"",""LastModified"":""2012-03-08T23:42:13.8681395+08:00""}");
            var result = client.UploadData("http://localhost:1405/api/contacts/4", "PUT", data);
            Console.WriteLine(Encoding.UTF8.GetString(result));
        }
    }
}

When I run the client, the following request is being sent:

PUT /api/contacts/4 HTTP/1.1
Content-Type: application/json
Host: localhost:1405
Content-Length: 119
Expect: 100-continue
Connection: Keep-Alive

{"Id":3,"Name":"mmm","Phone":"000 000 0000","Email":"[email protected]","LastModified":"2012-03-08T23:42:13.8681395+08:00"}

and I get the correct result from the server. So I guess that the request you are showing is not the actual request that's being sent to the server.