Throw error when unknown property found in input API request?

Question

Currently I'm passing Rest Request with JSON string as filter to Web API as follows,

http://localhost:13825/api/values/get?filter={"Name":"abcdef","Address":"Something"}

I have a class like follows,

Public class Customer
{
  public string Name{get;set;}
  public string Address{get;set;}
}

When I use the following code to parse JSON string to a class object it works fine,

public string Get(Customer filter)
{

}

The problem is, When I pass filter like follows,

filter={"Name":"abcdef","Adess":"Something"}

my code assigns null value to Address property of Customer class but i wanted to throw an error when a property from JSON string is not found in any of the class property.

We can use MissingMemberHandling.Error but it will throw error when additional properties with all the properties what we defined in class . Here the problem case is different , I wont pass Address and Name properties every time. I may or may not pass both.

So I cant give required property.

I need to throw an error when unknown property is found in input JSON string.

possible duplicate of [Can you detect if an object you deserialized was missing a field with the JsonConvert class in Json.NET](http://stackoverflow.com/questions/21030712/can-you-detect-if-an-object-you-deserialized-was-missing-a-field-with-the-jsonco) — Adriano Repetti, May 27 '15 at 11:39
@Alex maybe the address is optional, in which case it *can* be null. What the OP wants to prevent is typos. — dcastro, May 27 '15 at 11:44

dcastro · Accepted Answer · 2015-05-27T12:02:30.983

You can set JsonSerializerSettings.MissingMemberHandling to MissingMemberHandling.Error.

Gets or sets how missing members (e.g. JSON contains a property that isn't a member on the object) are handled during deserialization.

If you want to do this globally, for all controllers, simply add this to global.asax

GlobalConfiguration.Configuration.Formatters.JsonFormatter.SerializerSettings.MissingMemberHandling = MissingMemberHandling.Error;

If you want to do this for a specific action/controller, then you have to implement IControllerConfiguration:

public class RejectUnrecognizedPropertiesAttribute : Attribute, IControllerConfiguration 
{
    public void Initialize(HttpControllerSettings controllerSettings, HttpControllerDescriptor controllerDescriptor)
    {
        controllerSettings.Formatters.Remove(controllerSettings.Formatters.JsonFormatter);

        var formatter = new JsonMediaTypeFormatter
        {
            SerializerSettings = 
            {
                MissingMemberHandling = MissingMemberHandling.Error
            }
        };

        controllerSettings.Formatters.Add(formatter);
    }
}

And simply apply the [RejectUnrecognizedProperties] attribute to your action/controller.

score 0 · Answer 2 · answered May 27 '15 at 11:40

You can actually just use the "Required" annotation on the required property in your model. Like this:

Public class Customer
{
  [Required]
  public string Name{get;set;}
  [Required]
  public string Address{get;set;}
}

Then you can do a check in the action:

        if (ModelState.IsValid)
        {
            // Do something with the Customer.

            return new HttpResponseMessage(HttpStatusCode.OK);
        }
        else
        {
            return Request.CreateErrorResponse(HttpStatusCode.BadRequest, ModelState);
        }

score 0 · Answer 3 · answered May 27 '15 at 11:41

With JSON.net, you could define properties like this:

public class Customer
{
    [JsonProperty(Required = Required.Always)]
    public string Name{ get; set; }

    [JsonProperty(Required = Required.Always)]
    public string Address{ get; set; }
}

and then deserialize it this way:

var CustomerInstance = (Customer)JsonConvert.DeserializeObject(JSONString, typeof(Customer));

This would throw an exception if required data is not present.

Throw error when unknown property found in input API request?

3 Answers3

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