How to find reason "A circular reference was detected while serializing.... 'System.Reflection.RuntimeModule' - asp.net

Question

I have setup the view MyView.chstml with two submit action. but give me "A circular reference was detected while serializing an object of type 'System.Reflection.RuntimeModule'. How to troubleshoot easily ?
#using (Html.BeginForm("MyView", "Worker", FormMethod.Post, new { enctype = "multipart/form-data", #name = "formWorker" }))
{
#Html.AntiForgeryToken()
<div class="form-horizontal" id="divWork"> ....
<div class="form-group">
<button id="btnSubmit" class="btn btn-success" type="submit" value="Work1">Work1</button>
</div>
<div id="Dynamictable" class="table-responsive hidden" name="dtable">
<table class="table table-bordered" id="dctable" name="dctable"></table>
</div>
<div id="dialogsubmit" title="second submit">
<div id="dialog-content" name="dialog-content" class="form-control hidden"> </div>
</div>
</div>
then in script
(function () {
//strangely the below ajax is never called
$('#formWorker').submit(function () {
debugger;
$.ajax({
url: this.action,
type: this.method,
data: $(this).serialize(),
success: function (result) {
debugger;
bootbox.alert(result);
}
});
// it is important to return false in order to
// cancel the default submission of the form
// and perform the AJAX call
return false;
});
}
$("#btnSubmit").click(function () {
if(document.getElementById('dctable').getElementsByTagName("tr").length < 1)
{
aRow = document.all("dctable").insertRow();
var oCell = aRow.insertCell();
oCell = newRow.insertCell();
oCell.innerHTML = '<input type="submit" name="submit2" value="submit2" />';
**//strangely if i replace the above RHS with below, it act as submit halft submit form (half becuase the FormCollection object in HttpPost method of controller lacks key submit2 and also HttpPostedFileBase object came as null in controller method ,**
*//'<button id="submit2" name="submit2" class="btn submit2" value="submit2" ><i class="fa fa-search"></i> submit2</button>'*
return false;
}
});
</script>
in controller
[HttpGet]
public ActionResult Worker()
{
return View();
}
[HttpPost]
[ValidateAntiForgeryToken]
public ActionResult Worker(HttpPostedFileBase file, FormCollection form)
{
string value = form["submit2"]; //half submit form as it is null in additon to file is null. if i use commented RHS , all good here, but no option in view to process the output in same view.
IEnumerable<object> data = Enumerable.Empty<object>();
if (value != null) // key doesn't exist
{
//process here and and return json to shown result on same page using popup/alert.
return this.Json(
new
{
Result = data.ToList()
}, JsonRequestBehavior.AllowGet
);
}
return PartialView("anoterhView", data.ToList());
}

Answer 1

A circular reference exception is generally thrown when the JSON serializer initiates a loop that causes effectively an infinite loop of serializing. This happens when you look at the schema of your serializable properties. For example:
Take the two classes below:
public class Node
{
public Node Parent { get; set; }
}
public class Parent : Node
{
public List<Node> Children { get; set; } = new List<Node>();
}
As you can see we have two simple classes, a Node class which has a public property Parent which is type Node. Now if we look at the Parent class it derrives from Node and has the property Children which is a List<Node>. This is where we will start to have circular dependency issues. Consider the following simple method.
public string SerializeJsonObject()
{
var parent = new Parent();
var child = new Node();
child.Parent = parent;
parent.Children.Add(child);
return Json(parent);
}
This method constructs a Parent object parent and then a Node object child. Next we set the Parent property of child to the parent instance. Then we Add the child to the parent's Children list.
Now consider the serialization of parent.
-- Parent Item
-- Parent: null no procesing
-- Children : Serialize each Node object
-- Node 1
-- Parent
-- Parent: null no processing
-- Children:
-- Node 1
-- Parent
--Parent: null no processing
--Children:
-- Node 1
..... continues forever never finishing serializing Node 1
From this we can see our circular dependency is the Parent property however it is only a circular reference because then Parent has a reference to the Node in the Children collection. Therefore the serializer can never finish serializing the object.
Now this isn't limited to lists we can look at a similar example where two classes have a reference to each other and are both serializable. Consider the following class.
public class Node
{
public string Name { get; set; }
public Node Previous { get; set; }
public Node Next { get; set; }
}
This class has a dependency on Node for both the Previous and Next property. Therefore given a method of constructing a small dataset.
public static object SerailizeANode()
{
Node first = null;
Node previous = null;
for(var i = 0; i < 10; i++)
{
var current = new Node();
current.Name = $"Node {i}";
if(previous != null)
{
previous.Next = current;
current.Previous = previous;
}
previous = current;
if (first == null)
first = current;
}
return Json(first);
}
This is really simple but ends up with 10 objects where 1-9 have a dependency on the Next node and objects 2-10 have a dependency to the Previous node. So given the serialization of first
-- first
-- Name: Node 0
-- Previous: Null
-- Next:
-- Name: Node 1
-- Previous
-- Name: Node 0
-- Previous: null
-- Next:
-- Name: Node 1
-- Previous:
-- Name: Node 0
-- Previous: null
-- Next:
--Name: Node 1
continues on forever.
Again as we see by the dependency serialization of the Property (Previous & Next) cause the serializer to hit a circular reference (infinite loop) and throws an exception.
My expectation is there a similar issue in the data that is returning to the browser through the section nicely commented out.
//process here and and return json to shown result on same page using popup/alert.
return this.Json(new
{
Result = data.ToList()
}, JsonRequestBehavior.AllowGet);
If you need more information could you please post the schema of the classes being returned in the commented out section.