Invalid operation exception when passing JSON string

Question

This is what I have done

        bool query = ( from n in CDC.NCDCPoints
                where n.EVENT_TYPE_ID == et
                where n.BeginDate == b
                where n.EndDate == e
                select n).Count()>0;

       var dupli = (from n in CDC.NCDCPoints
                     where n.EVENT_TYPE_ID == et
                     where n.BeginDate == b
                     where n.EndDate == e
                     select n);
        if (query)
        {
         return new JavaScriptSerializer().Serialize(dupli);
        }
        else
        {
            return "No duplicate";
        }

When I try to convert it into a JSON string, I get a circular reference error. The error occurs at the Serialize step. So, I think probably I get an error because it is an invalid object or something. Do I need to use something like Iqueryable or something. Please help me in getting rid of this error?

Any reason you have multiple wheres instead of just using &&, or defining dupli outside of the scope in which you use it? — Cᴏʀʏ
– Cᴏʀʏ, Commented Jun 16, 2011 at 4:10

Cᴏʀʏ · Accepted Answer · 2011-06-16 04:24:36Z

1

I think this is a little more straightforward. Also, you might need a concrete set of objects in order to serialize them (instead of an IQueryable<T> or IEnumerable<T> that you're getting from the LINQ query, so I threw in a .ToList() to get a List<T>, where T is whatever type is in your NCDCPoints collection. This is completely untested, just so you know.

To avoid the circular reference you mentioned, you can use the technique I added to the LINQ query:

var query = (from n in CDC.NCDCPoints
             where n.EVENT_TYPE_ID == et && n.BeginDate == b && n.EndDate == e
             select new 
             {
                 EventTypeId = n.EVENT_TYPE_ID,
                 BeginDate = n.BeginDate,
                 EndDate = n.EndDate,
                 ... // add the other properties you need on the client side
             });

if (query.Any())
{
    return new JavaScriptSerializer().Serialize(query.ToList());
}
else
{
    return "No duplicate";
}

edited Jun 16, 2011 at 4:24

answered Jun 16, 2011 at 4:14

Cᴏʀʏ

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4 Comments

nishanth yeddula Over a year ago

@Cory: I still get the same error of circular reference(which is some type invalid operation exception)..

Cᴏʀʏ Over a year ago

JavascriptSerializer uses reflection to serialize your list, but you must have a property that points back to the CDC.NCDCPoints list. A collection can't be serialized if it has circular references.

nishanth yeddula Over a year ago

@Carlson: Oh... So Can u please tell me another way to do this?

nishanth yeddula Over a year ago

K... I have 50 fields in there. So, Do i have any other way to proceed with this one.

Community · Accepted Answer · 2017-05-23 12:12:05Z

0

When I ran across the same problem, I did a quick research on why this happens on Entity Framework and came across a wonderful answer at Stack Overflow itself.

Read this: Is this bug ?...got reason behind circular reference ... how to solve but?

You should never serialize the LINQ to SQL (or Entity Framework) classes. Even though Microsoft has placed [DataContract] and other attributes on these classes, they should not be serialized.

Instead, design a set of classes that correctly matches what you want to have serialized.

Try these steps.

Create a mock class called NCDCPointsMock

public class NCDCPointsMock
{
    public DateTime? BeginDate { get; set; }
    public DateTime? EndDate { get; set; }
    public int EVENT_TYPE_ID { get; set; }
    // add another dfields you might have in the original NCDCPoints class
    //example        
    //public int ID { get; set; }
}

Now modify your code like this.

var query = CDC.NCDCPoints
    .Select(n => n.EVENT_TYPE_ID == et 
        && n.BeginDate == b 
        && n.EndDate == e );
if (query.Any())
{
    var points = query.ToList();]
    List<NCDCPointsMock> duplicates = new List<NCDCPointsMock>();
    foreach(var point in points)
    {
        NCDCPointsMock dupli = new NCDCPointsMock();
        dupli.ID = point.ID;
        dupli.BeginDate = point.BeginDate;
        dupli.EndDate = point.EndDate;
        dupli.EVENT_TYPE_ID = point.EVENT_TYPE_ID;
        duplicates.Add(dupli);
    }
    return new JavaScriptSerializer().Serialize(dupli);
}
else
{
    return "No duplicate";
}

Or you can try something from here. But that will make the model different from database.

LINQ to SQL and Serialization

edited May 23, 2017 at 12:12

CommunityBot

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answered Jun 16, 2011 at 4:39

codeandcloud

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2 Comments

nishanth yeddula Over a year ago

hey..My problem is that I have so many fields in the NCDCPoints. And they are dynamic. So, apart from serialization , do i have any other way of doing this?

codeandcloud Over a year ago

@nishanth yeddula: actually i wouldn't have posted this if i had seen cory's answer before hand. slightly different approach but in effect the same.

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