SignalR : Could not cast or convert from System.String to System.Collections.Generic.IEnumerable
asp.net, jquery, json, signalr
Solution
Ok, this is why I was getting this error.
In the `jquery.signalr-2.0.0.js` file, set a breakpoint at line 2578
connection.data = connection.json.stringify(subscribedHubs);
Step into that function call and see if your `JSON.stringify` method has been overridden. In my case, I was using an older version of `prototype.js` that was overriding the `JSON.stringify` function, causing the wrong parsing to occur.
Also, try running the following command from the F12 Developer Tools:
JSON.stringify([{name:"testhub"}]);
if should return `"[{"name":"testhub"}]"`, if it returns `""[{\"name\": \"testhub\"}]""` your stringify has been compromised.
Problem
Following is my client code that I am using on two different pages: ``` <script src='<%= Page.ResolveUrl("~/resources/js/jquery-1.6.4.min.js") %>' type="text/javascript"></script>re <script type="text/javascript"> jQuery.noConflict(); </script> <script src='<%= Page.ResolveUrl("~/resources/js/jquery.signalR-1.2.0.min.js") %>' type="text/javascript"></script> <script src='<%= Page.ResolveUrl("~/signalr/hubs") %>' type="text/javascript"></script> <script type="text/javascript"> jQuery(function () { // Declare a proxy to reference the hub. var usr = jQuery.connection.notificationHub; jQuery.connection.hub.logging = true; jQuery.connection.hub.qs = "clientId=arif";// +readCookie("personId"); jQuery.connection.hub.start().done(function () { }); usr.client.showUsersOnLine = function (data) { }; }); </script> ``` On one page it gets connected and is working ok, but on another page its giving me following error : ``` [ArgumentException: Could not cast or convert from System.String to System.Collections.Generic.IEnumerable`1[Microsoft.AspNet.SignalR.Hubs.HubDispatcher+ClientHubInfo].] Newtonsoft.Json.Utilities.ConvertUtils.EnsureTypeAssignable(Object value, Type initialType, Type targetType) +241 Newtonsoft.Json.Utilities.ConvertUtils.ConvertOrCast(Object initialValue, CultureInfo culture, Type targetType) +123 Newtonsoft.Json.Serialization.JsonSerializerInternalReader.EnsureType(JsonReader reader, Object value, CultureInfo culture, JsonContract contract, Type targetType) +238 [JsonSerializationException: Error converting value "[{"name": "notificationhub"}]" to type 'System.Collections.Generic.IEnumerable`1[Microsoft.AspNet.SignalR.Hubs.HubDispatcher+ClientHubInfo]'. Path '', line 1, position 35.] Microsoft.Owin.Host.SystemWeb.Infrastructure.<>c__DisplayClass1.<GetRethrowWithNoStackLossDelegate>b__0(Exception ex) +27 Microsoft.Owin.Host.SystemWeb.Infrastructure.ErrorState.Rethrow() +34 Microsoft.Owin.Host.SystemWeb.CallContextAsyncResult.End(IAsyncResult result) +49 Microsoft.Owin.Host.SystemWeb.OwinHttpHandler.EndProcessRequest(IAsyncResult result) +7 System.Web.CallHandlerExecutionStep.System.Web.HttpApplication.IExecutionStep.Execute() +9628972 System.Web.HttpApplication.ExecuteStep(IExecutionStep step, Boolean& completedSynchronously) +155 ``` The only difference I see is : While calling the the negotiate utl the 'connectionData' param is different : For the page where its working its like : ``` connectionData [{"name":"notificationhub"}] ``` And for the page where it's not working looks like : ``` connectionData "[{\"name\": \"notificationhub\"}]" ``` Can anybody please suggest what am I actually missing or what should the check ?