"Value cannot be null" when passing null arguments to SignalR client-side proxy

Question

Using SignalR (v2.0.2) I'm getting this exception:

Value cannot be null.
Parameter name: o
   at Newtonsoft.Json.Utilities.ValidationUtils.ArgumentNotNull(Object value, String parameterName)
   at Newtonsoft.Json.Linq.JToken.FromObjectInternal(Object o, JsonSerializer jsonSerializer)
   at Newtonsoft.Json.Linq.JToken.FromObject(Object o, JsonSerializer jsonSerializer)
   at Microsoft.AspNet.SignalR.Client.Hubs.HubProxy.Invoke[T](String method, Object[] args)

I'm calling the HubProxy with reflection, and I am passing in some null arguments that are triggering this error (aka, some items in the Object[] args are null). However, passing null for an argument to a method is a perfectly legitimate thing to do. Is this a bug in SignalR in that it is trying to serialize null parameters or is it a bug in Json.NET (v6.0.1) in that it shouldn't attempt to serialize a null object?

@tweellt, I checked that link. It seems to be a similar error but not a similar situation. — Brannon
– Brannon, Commented Mar 21, 2014 at 19:06
@Dmitry, I have not attempted to replace the serialization in SignalR with any other framework. I really like Json.NET and don't want to replace it. I use it numerous other places in my software. — Brannon
– Brannon, Commented May 12, 2014 at 15:20

dadude999 · Accepted Answer · 2016-04-29 22:13:10Z

0

Turns out this is a known bug in SignalR that has been fixed and will be included in the upcoming 2.2.1 release. See their ticket here.

answered Apr 29, 2016 at 22:13

dadude999

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3 Comments

Brannon Over a year ago

As of October 2016 it appears that this is still an active argument. No fix is permanent yet.

dadude999 Over a year ago

Their latest release lists this as fixed: github.com/SignalR/SignalR/releases/tag/2.2.1.

Mike Flynn Over a year ago

Still happening in 2.4

shA.t · Accepted Answer · 2015-05-04 10:17:30Z

0

You can try to override SignalR hubs invocation method, for example: customize Microsoft.AspNet.SignalR.AuthorizeAttribute like this:

public override bool AuthorizeHubMethodInvocation(IHubIncomingInvokerContext hubIncomingInvokerContext, bool appliesToMethod)
{

}

Then before invoke, you can check your request and make some processing if needed.

edited May 4, 2015 at 10:17

shA.t

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answered May 4, 2015 at 8:28

LIU YUE

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1 Comment

Nilesh Over a year ago

Please provide more details.

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