Circular Reference. I really need help ... thanks.

  • Thread starter Thread starter shapper
  • Start date Start date
S

shapper

Hello,

On an ASP.NET MVC project I am getting a list of Tags which names
start with a string contained on the variable "q".

Everything works fine if no Post is related to Tags.
When there is relation I start to get a Circular Reference error.

I have been trying to solve this problem for days!
I can't find the reason for this, either in my SQL or C# code.

I am posting both codes ... just in case:

C# LINQ code:

public JsonResult Filter(string q, int limit) {

var list = (from t in database.Tags
where t.Name.StartsWith(q)
orderby t.Name
select t);
List<Tag> tags = (limit > 0 ? list.Take(limit) : list).ToList();
return this.Json(tags);

}

SQL Tables:

Code: 
-- Files
create table dbo.Files
(
FileID uniqueidentifier not null
constraint PK_File primary key clustered,
CreatedAt datetime null,
Description nvarchar(2000) null,
IsPublished bit null,
Path nvarchar(800) null,
Title nvarchar(400) null,
UpdatedAt datetime null
)

-- Posts
create table dbo.Posts
(
PostID uniqueidentifier not null
constraint PK_Post primary key clustered,
Body nvarchar(max) null,
CreatedAt datetime null,
IsPublished bit null,
Title nvarchar(400) null,
UpdatedAt datetime null
)

-- Tags
create table dbo.Tags
(
TagID uniqueidentifier not null
constraint PK_Tag primary key clustered,
[Name] nvarchar(100) null
)

-- FilesTags
create table dbo.FilesTags
(
FileID uniqueidentifier not null,
TagID uniqueidentifier not null,
constraint PK_FilesTags
primary key clustered (FileID, TagID),
constraint FK_FilesTags_Files
foreign key(FileID)
references dbo.Files(FileID)
on delete cascade,
constraint FK_FilesTags_Tags
foreign key(TagID)
references dbo.Tags(TagID)
on delete cascade
)

-- PostsTags
create table dbo.PostsTags
(
PostID uniqueidentifier not null,
TagID uniqueidentifier not null,
constraint PK_PostsTags
primary key clustered (PostID, TagID),
constraint FK_PostsTags_Posts
foreign key(PostID)
references dbo.Posts(PostID)
on delete cascade,
constraint FK_PostsTags_Tags
foreign key(TagID)
references dbo.Tags(TagID)
on delete cascade
)

DATA in Tables (All other tables are empty):

Posts

PostID: 78ef0b05-ca4c-4df8-88c9-2858d24fa4e3
Body: <p>Test</p>
CreateAt: 03-09-2008 22:35:25
IsPublished: True
Title: This is the title
UpdatedDate: 03-09-2008 22:35:25

Tags

TagID: e2ec18a7-d668-477b-977b-183989df2a65
Name: Net

TagID: dbf4465a-d0f6-4145-831d-b1ce1363dd16
Name: New York

TagID: 0ea15666-155b-4237-a871-d905a2685f45
Name: Australia

PostsTags

TagID: e2ec18a7-d668-477b-977b-183989df2a65
PostID: 78ef0b05-ca4c-4df8-88c9-2858d24fa4e3

TagID: dbf4465a-d0f6-4145-831d-b1ce1363dd16
PostID: 78ef0b05-ca4c-4df8-88c9-2858d24fa4e3

My Linq code is automaticly generated by LinqToSQL in VS2008.

I don't see any problem in my code or data but I get the error:

A circular reference was detected while serializing an object of type
'MyApp.Models.Post'

I detected the error in FireFox FireBug because the AutoComplete most
of the time does not work.

Does anyone sees anything wrong?!

Thanks,
Miguel
 
shapper said:
Everything works fine if no Post is related to Tags.
When there is relation I start to get a Circular Reference error.

I have been trying to solve this problem for days!
I can't find the reason for this, either in my SQL or C# code.

I am posting both codes ... just in case:

C# LINQ code:

public JsonResult Filter(string q, int limit) {

var list = (from t in database.Tags
where t.Name.StartsWith(q)
orderby t.Name
select t);
List<Tag> tags = (limit > 0 ? list.Take(limit) : list).ToList();
return this.Json(tags);

}
Click to expand...

Without the definition for Json() method, this doesn't tell much.
 
Without the definition for Json() method, this doesn't tell much.
Click to expand...

JSON is from ASP.NET MVC Preview 5...

I found the a explanation for this in: http://www.west-wind.com/Weblog/posts/147218.aspx

I was reading the article but its explanation implies changes to the
model which he also says that have a downside.

In this case I am serializing a list of Tags ... each Tag has 2
properties: TagID and Name ...

All I need is only the names of the selected Tags ... so couldn't I
just pick the Names of all Tags in the list create an object or a new
list and serialize it?

Maybe a list of String? An Array?

Maybe this would solve the problem without needing to change the
model ...

Any idea how to do this?

Thanks,

Miguel
 
JSON is from ASP.NET MVC Preview 5...

I found the a explanation for this in:http://www.west-wind.com/Weblog/posts/147218.aspx

I was reading the article but its explanation implies changes to the
model which he also says that have a downside.

In this case I am serializing a list of Tags ... each Tag has 2
properties: TagID and Name ...

All I need is only the names of the selected Tags ... so couldn't I
just pick the Names of all Tags in the list create an object or a new
list and serialize it?

Maybe a list of String? An Array?

Maybe this would solve the problem without needing to change the
model ...

Any idea how to do this?

Thanks,

Miguel
Click to expand...

Just solved it:

// Define list
var list = (from t in database.Tags
where t.Name.StartsWith(q)
orderby t.Name
select t.Name);

// Define tags
string[] tags = (limit > 0 ? list.Take(limit) : list).ToArray();

// Return tags
return this.Json(tags);

Thanks,
Miguel
 
I ran into the same problem and THE ONE OF SOLUTION IS to

Use [ScriptIgnore] atribute .. it will solve the problem.

add system.web.extensions reference and add namespace:

Using System.Web.Script.Serialization.

If you still have questions..Read on..for some detailed explanation..

i have a User class with..

using System;

using System.Collections.Generic;

using System.Linq;

using System.Web;

using Iesi.Collections.Generic;

using System.Runtime.Serialization;

namespace RAPortal.Core.Entities

{

public class User

{

private int _userId;

private string _firstName;

private string _lastName;

private IList<Application> _applications;

private IList<Group> _groups;

private IList<ApplicationRequest> _applicationRequests;

Properties..

public virtual int UserId

{

get

{

return _userId;

}

set

{

_userId = value;

}

}

public virtual string Title

{

get

{

return _title;

}

set

{

_title = !String.IsNullOrEmpty(value) ? value.ToUpper().Trim() : null;

}

}

public virtual IList<Group> Groups

{

get

{

return _groups;

}

set

{

_groups = value;

}

}

public virtual IList<UserPrivilege> UserPrivileges

{

get

{

return _userPrivileges;

}

set

{

_userPrivileges = value;

}

}

public virtual IList<UserRole> UserRoles

{

get

{

return _userRoles;

}

set

{

_userRoles = value;

}

}

....so on...

and I have Groups class..

using System;

using System.Collections.Generic;

using System.Linq;

using System.Web;

using System.Web.Script.Serialization;

using System.Runtime.Serialization;

namespace RAPortal.Core.Entities

{

public class Group

{

private int _groupId;

private string _name;

private IList<User> _users;

public virtual int GroupId

{

get

{

return _groupId;

}

set

{

_groupId = value;

}

}

public virtual string Name

{

get

{

return _name;

}

set

{

_name = !String.IsNullOrEmpty(value) ? value.ToUpper().Trim() : null;

}

}

[ScriptIgnore]

public virtual IList<User> Users

{

get

{

return _users;

}

set

{

_users = value;

}

}

}

}

Since User is referenced in the groups.. the json think that it is Circular reference and It will throw an exception..so the fix is to add [ScriptIgnore] on top of the User. And add the reference and namespace to this class like it..

It solved my problem .. I am sure there are better ways out there !!! Cheers...

And remember you should add [scriptIgnore] only in the groups class and not in the Users class..



Posted as a reply to:

Re: Circular Reference. I really need help ... thanks.


Without the definition for Json() method, this doesn't tell much.

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