c# - Possible to look for Key that does not exist in Json.net

Question

I got a couple different formats that come in but I can't figure out how to handle them all because when I try to find by key json.net crashes. I was hoping it would just return null.

foreach (var item in jsonObj)
{
    var msg = item.Value["Msg"];
    if (msg != null)
    {
       txtErrors.Text += msg + Environment.NewLine;
    }
}

// format one

{[UserNotFound, {
  "SeverityType": 3,
  "ValidationType": 2,
  "Msg": "Email Not Found"
}]}

my code works.

// format 2 (came because I did not catch an exception on serverside)

{
  "Message": "An error has occurred.",
  "ExceptionMessage": "Object reference not set to an instance of an object.",
  "ExceptionType": "System.NullReferenceException",
  "StackTrace": "  "
}

I can of course fix this and catch the exception. However if I ever forget again, I rather not have it crash on the client as well. So I would love to just print out the "message" but I don't get how to do it so it does not crash on var msg = item.Value["Msg"];

The error I get when it tries to do var msg = item.Value["Msg"];

System.InvalidOperationException was unhandled
  Message=Cannot access child value on Newtonsoft.Json.Linq.JValue.
  StackTrace:
       at Newtonsoft.Json.Linq.JToken.get_Item(Object key)
       at Fitness.WindowsPhone7.UI.MainPage.<btnSignIn_Click>b__0(IRestResponse response)
       at RestSharp.RestClientExtensions.<>c__DisplayClass1.<ExecuteAsync>b__0(IRestResponse response, RestRequestAsyncHandle handle)
       at RestSharp.RestClient.ProcessResponse(IRestRequest request, HttpResponse httpResponse, RestRequestAsyncHandle asyncHandle, Action`2 callback)
       at RestSharp.RestClient.<>c__DisplayClass3.<ExecuteAsync>b__0(HttpResponse r)
       at RestSharp.RestClient.<>c__DisplayClass5.<>c__DisplayClass7.<ExecuteAsync>b__2(Object s)
       at System.Reflection.RuntimeMethodInfo.InternalInvoke(RuntimeMethodInfo rtmi, Object obj, BindingFlags invokeAttr, Binder binder, Object parameters, CultureInfo culture, Boolean isBinderDefault, Assembly caller, Boolean verifyAccess, StackCrawlMark& stackMark)
       at System.Reflection.RuntimeMethodInfo.InternalInvoke(Object obj, BindingFlags invokeAttr, Binder binder, Object[] parameters, CultureInfo culture, StackCrawlMark& stackMark)
       at System.Reflection.MethodBase.Invoke(Object obj, Object[] parameters)
       at System.Delegate.DynamicInvokeOne(Object[] args)
       at System.MulticastDelegate.DynamicInvokeImpl(Object[] args)
       at System.Delegate.DynamicInvoke(Object[] args)
       at System.Windows.Threading.DispatcherOperation.Invoke()
       at System.Windows.Threading.Dispatcher.Dispatch(DispatcherPriority priority)
       at System.Windows.Threading.Dispatcher.OnInvoke(Object context)
       at System.Windows.Hosting.CallbackCookie.Invoke(Object[] args)
       at System.Windows.Hosting.DelegateWrapper.InternalInvoke(Object[] args)
       at System.Windows.RuntimeHost.ManagedHost.InvokeDelegate(IntPtr pHandle, Int32 nParamCount, ScriptParam[] pParams, ScriptParam& pResult)

Answer 1

Assuming that you use Newtonsoft.Json:

You can use JObject to test if there is a property or not:

JObject jObj; //initialized somewhere, perhaps in your foreach
var msgProperty = jObj.Property("msg");

//check if property exists
if (msgProperty != null) {
    var mag = msgProperty.Value;
} else {
    //there is no "msg" property, compensate somehow.
}