InvalidCastException mapping Json string onto Guid property

Question

Having theese POCOs:

public class UserRegistration
{
    [Required]
    public ApiKey ApiKey { get; set; }
    ...
}

public class ApiKey 
{
    [Required]
    public Guid AppKey { get; set; }
    ...
}

and this Json:

{
    "apiKey": {
      "appKey": "D8B4DE20-5654-43B0-B3F6-FDA416087FDE"
    }
}

I'm getting an exception:

System.InvalidCastException: Unable to cast object of type 'System.Guid' to type 'System.String'.
at System.Web.Http.ApiController.d__b.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
at System.Web.Http.Dispatcher.HttpControllerDispatcher.d__0.MoveNext()

calling this an ASP.NET Web API controller:

public HttpResponseMessage Put([FromBody]UserRegistration userRegistration)
{
}

If change property type form Guid to string, all works fine, but I want Guid. Is such scenario supported?

This should be helpful http://stackoverflow.com/questions/13640463/json-net-exception-when-deserializing-an-array-of-guids — Ehsan, Jul 23 '13 at 17:36
@EhsanUllah: Does it mean Guid is not supported and I need to accept string and then parse it manually? — abatishchev, Jul 23 '13 at 18:28
The post linked above is talking about being unable to deserialize an array of guids directly - but you've got just this one guid on the object, right? Is the exception text complete btw? It's saying unable to cast Guid but it's not saying to which type - can you post the full message? — Joanna Derks, Jul 23 '13 at 19:16
@JoannaTurban: Sorry, exception message turned out to be truncated. Fixed. Guid to String. — abatishchev, Jul 23 '13 at 20:11
@EhsanUllah: actually it's supported pretty fine, see my own answer below. — abatishchev, Jul 23 '13 at 20:47

score 3 · Accepted Answer · answered Jul 23 '13 at 20:47

3

What is not obviously following from the exception stack trace, problem was not in mapping but in validation attribute decoration:

[Required]
[StringLength(36)] // NO-NO!
public Guid AppKey { get; set; }

answered Jul 23 '13 at 20:47

abatishchev

98,240
88
296
433

InvalidCastException mapping Json string onto Guid property

1 Answers1