I have the following entity
public class Meeting
{
[Key]
public int Id { get; set; }
public Guid SubjectId { get; set; }
public string FirstName { get; set; }
public string LastName { get; set; }
[Required]
public string Email { get; set; }
private ICollection<MeetingPeriod> _meetingTimes;
public virtual ICollection<MeetingPeriod> MeetingTimes
{
get { return _meetingTimes ?? (_meetingTimes = new Collection<MeetingPeriod>()); }
protected set { _meetingTimes = value; }
}
}
Got a few questions:
When I get a record I would like all the MeetingTimes to be sorted by default. Is this possible? I tried to return _meetingTimes.OrderBy but then I could not add any more meeting times as it was a readonly list.
I have added override Equals() to MeetingPeriod object. However when I try to compare MeetingTimes to an array of MeetingPeriod seems like the Equal() isn't getting called. What is going on here? It does get called correctly elsewhere. Seems like something to do with ICollection?
Related
Having an issue with projection and getting child objects to load. The following is simplified code to represent the logic I'm trying to implement, not the actual code.
public class TicketItem
{
public int TicketItemId { get; set; }
public string TicketReason { get; set; }
public Station Station { get; set; }
public TicketOwner TicketOwner { get; set; }
}
public class Station
{
public int StationId { get; set; }
public string Name { get; set; }
}
public class TicketOwner
{
public int TicketOwnerId { get; set; }
public Employee Employee { get; set; }
public Organization Organization { get; set; }
}
public class Employee
{
public int EmployeeId { get; set; }
public string FirstName { get; set; }
public string LastName { get; set; }
}
public class Organization
{
public int OrganizationId { get; set; }
public string Code { get; set; }
public string Name { get; set; }
}
public class CommonReasons
{
public int CommonReasonId { get; set; }
public string Reason { get; set; }
}
public TicketItem GetById(int id)
{
var query = from i in _dataContext.TicketItems
.Include("Station")
.Include("TicketOwner.Employee")
.Include("TicketOwner.Organization")
join r in _dataContext.CommonReasons on i.TicketReason equals r.CommonReasonId.ToString() into r1
from r2 in r1.DefaultIfEmpty()
where i.TicketItemId == id
select new TicketItem {
TicketItemId = i.TicketItemId,
TicketReason = r2.Reason == null ? i.Reason : r2.Reason,
Station = i.Station,
TicketOwner = i.TicketOwner
};
return query
.AsNoTracking()
.FirstOrDefault();
}
Most the code is self-explanatory. The part that is indirectly causing the trouble would be the relationship between TicketItem.TicketReason property (a string) and the CommonReasons entity. From the user interface side, the end-user has an input field of "Reason", and they can select from "common" reasons or input an adhoc reason. They original developer chose to have the TicketReason property contain either the key ID from the CommonReasons table (if the user selected from drop-down) or the adhoc reason typed in.
So, to handle this logic in the linq query, the only way I have found is to do a left join between TicketItem.TicketReason and CommonReasons.CommonReasonId, then use projection to modify the TicketReason column returning either the common reason text or adhoc text. If there is a different way to do this that would get me around the trouble I'm having with projection/include, I'm all ears.
For the "reason" logic, this query works, returning the proper text. The trouble is that none of the "grand-child" objects are returning, i.e. TicketItem.TicketOwner.Employee, TicketItem.TicketOwner.Organization. How do I get those objects to return also?
Changing the structure of the tables would be an absolute last resort, just based on the amount of code that would have to change. There are other spots in the code that are using the above logic but don't need the child objects.
Any help would be appreciated. Hope I've explained enough.
EDIT: I originally worded this question very poorly, stating the problem was with JSON serialization. The problem actually happens when I'm converting from my base classes to my returned models using my custom mappings. I apologize for the confusion. :(
I'm using .NET Core 1.1.0, EF Core 1.1.0. I'm querying an interest and want to get its category from my DB. EF is querying the DB properly, no problems there. The issue is that the returned category has a collection with one interest, which has one parent category, which has a collection with one interest, etc. When I attempt to convert this from the base class to my return model, I'm getting a stack overflow because it's attempting to convert the infinite loop of objects. The only way I can get around this is to set that collection to null before I serialize the category.
Interest/category is an example, but this is happening with ALL of the entities I query. Some of them get very messy with the loops to set the relevant properties to null, such as posts/comments.
What is the best way to address this? Right now I'm using custom mappings that I wrote to convert between base classes and the returned models, but I'm open to using any other tools that may be helpful. (I know my custom mappings are the reason for the stack overflow, but surely there must be a more graceful way of handling this than setting everything to null before projecting from base class to model.)
Classes:
public class InterestCategory
{
public long Id { get; set; }
public string Name { get; set; }
public ICollection<Interest> Interests { get; set; }
}
public class Interest
{
public long Id { get; set; }
public string Name { get; set; }
public long InterestCategoryId { get; set; }
public InterestCategory InterestCategory { get; set; }
}
Models:
public class InterestCategoryModel
{
public long Id { get; set; }
public string Name { get; set; }
public List<InterestModel> Interests { get; set; }
}
public class InterestModel
{
public long Id { get; set; }
public string Name { get; set; }
public InterestCategoryModel InterestCategory { get; set; }
public long? InterestCategoryId { get; set; }
}
Mapping functions:
public static InterestCategoryModel ToModel(this InterestCategory category)
{
var m = new InterestCategoryModel
{
Name = category.Name,
Description = category.Description
};
if (category.Interests != null)
m.Interests = category.Interests.Select(i => i.ToModel()).ToList();
return m;
}
public static InterestModel ToModel(this Interest interest)
{
var m = new InterestModel
{
Name = interest.Name,
Description = interest.Description
};
if (interest.InterestCategory != null)
m.InterestCategory = interest.InterestCategory.ToModel();
return m;
}
This is returned by the query. (Sorry, needed to censor some things.)
This is not .NET Core related! JSON.NET is doing the serialization.
To disable it globally, just add this during configuration in Startup
services.AddMvc()
.AddJsonOptions(options =>
{
options.SerializerSettings.ReferenceLoopHandling = ReferenceLoopHandling.Ignore;
}));
edit:
Is it an option to remove the circular references form the model and have 2 distinct pair of models, depending on whether you want to show categories or interests?
public class InterestCategoryModel
{
public long Id { get; set; }
public string Name { get; set; }
public List<InterestModel> Interests { get; set; }
public class InterestModel
{
public long Id { get; set; }
public string Name { get; set; }
}
}
public class InterestModel
{
public long Id { get; set; }
public string Name { get; set; }
public InterestCategoryModel InterestCategory { get; set; }
public class InterestCategoryModel
{
public long Id { get; set; }
public string Name { get; set; }
}
}
Note that each of the models has a nested class for it's child objects, but they have their back references removed, so there would be no infinite reference during deserialization?
I am facing the same issue as described in this question. Problem: my method GetAllConferences() returns correctly all the conferences from the DB, but when I return the result to the View from the controller return Ok(tripListVm) inly the first collection item is returned to the client. On the otehr side, by setting to null all the FK references (as pointed out in the SO question above) I can return correctly all the entities to the client, however this does not seem to me the proper way of proceeding.
EDIT: the solution was much simpler than I though. In the code below (I leave it in its original form for others to see it) I was not mapping the FK entities inside the ViewModel to Dto objects, but returning the model entity itself. That was the reason why I needed to null those inner references to make it work. By returning all Dtos objects, it works properly.
I have three entities involved with 1-many relationships:
public class Conference
{
public int Id { get; set; }
[Required]
[MaxLength(50)]
public string Name { get; set; }
public ICollection<Venue> Venues { get; set; }
public int? LocationId { get; set; }
public Location Location { get; set; }
}
public class Venue
{
public int Id { get; set; }
[Required]
[MaxLength(50)]
public string Name { get; set; }
public int? ConferenceId { get; set; }
public Trip Conference { get; set; }
public int? LocationId { get; set; }
public City City { get; set; }
}
public class City
{
public int Id { get; set; }
[Required]
[MaxLength(50)]
public string Name { get; set; }
public ICollection<Conference> Conferences { get; set; }
public ICollection<Venue> Venues { get; set; }
}
In the repository, I have a method that returns the conferences and the related entities (City and Venues):
public IEnumerable<Conference> GetAllConferences()
{
return _context.Conferences
.Include(t => t.Venues)
.Include(t => t.City)
.ToList();
}
In the controller I need to use the following code to return all the results:
var conferences = _repository.GetAllConferences();
if (conferences.Any())
{
var conferenceListVm = trips.ToConferenceVmList();
//Without setting the FK references to null, I can return only the first result of the collection
foreach (var vm in conferenceListVm)
{
foreach (var pm in vm.PoinOfInterests)
{
pm.Trip = null;
}
vm.Location.Conferences = null;
vm.Location.Venues = null;
}
return Ok(conferenceListVm);
}
public static ConferenceViewModel ToConferenceVm(this Conference conference)
{
var confVm = new ConferenceViewModel();
confVm.Name = conference.Name;
confVm.City = conference.City;
confVm.Venues = conference.Venues;
return tripVm;
}
public static IEnumerable<ConferenceViewModel> ToConferenceVmList(this IEnumerable<Conference> conferences)
{
return conferences.Select(c => c.ToConferenceVm()).ToList();
}
First of all I'm new to C#.
The error I get is:
Additional information: Unable to cast object of type 'UserGUI.MyItems' to type 'CommonBookLib.AbstractItem'.
They are 2 different classes:
public class MyItems
{
public string ItemName { get; set; }
public int CopyNumber { get; set; }
public int Guid { get; set; }
public DateTime? TimePrinted { get; set; }
public string Category { get; set; }
public string SubCategory { get; set; }
public bool? BestSeller { get; set; }
}
and
public class AbstractItem : IPropsDetails
{
public int CopyNumber { get; }
public string ItemName { get; }
public DateTime Time { get; }
public int Guid { get; }
public AbstractItem(int copyNumber, string itemName, DateTime time, int guid)
{
this.CopyNumber = copyNumber;
this.ItemName = itemName;
this.Time = time;
this.Guid = guid;
}
}
It happens when I do:
AbstractItem myItemsList = (AbstractItem)LibraryList.SelectedItem;
logicManager.Remove(myItemsList);
Well, as you can see, I have MyItems which are responsible for the DataBindings in my GUI and AbstractItem which responsible for implementing an addition operation to where my data is saved.
Since I did not managed my code well I got into this situation and I really do not want to change MyItems (delete and recode AbstractItem).
How can I Convert the two?
By the way, I know AbstractItem has only 4 properties while MyItems has more.
However, I have children with the exact same properties of AbstractItem.
Any help would be appreciated. Thanks in advance!
Remove fields from the MyItems class that are also present in AbstractItem, and then have MyItems derive from it instead.
You'll have to add a constructor to MyItems that passes the required values to the base constructor, or add an empty constructor to the base class.
public class MyItems : AbstractItem
{
public MyItems(int copyNumber, string itemName, DateTime time, int guid)
:base(copyNumber, itemName, time, guid)
{
}
public DateTime? TimePrinted { get; set; }
public string Category { get; set; }
public string SubCategory { get; set; }
public bool? BestSeller { get; set; }
}
You can make MyItems inherit AbstractItem, or make a method that handle the conversion between them.
You seem to need a mapper more than a cast. Look at AutoMapper or write your own routine as suggested by habibhassani. Also, Grant's answer is very good.
But your question was about casting so here I show how you can implement a casting operator so that your cast would work. This is not a technique you should reach for lightly. It puts a dependency on AbstractItem directly in MyItems and it is not the most discoverable pattern for maintainers of your code.
public class MyItems
{
public string ItemName { get; set; }
public int CopyNumber { get; set; }
public int Guid { get; set; }
public DateTime? TimePrinted { get; set; }
public string Category { get; set; }
public string SubCategory { get; set; }
public bool? BestSeller { get; set; }
public static explicit operator AbstractItem(MyItems myitems)
{
return new AbstractItem(myitems.CopyNumber, myitems.ItemName, myitems.TimePrinted, myitems.Guid);
}
}
A couple more observances. Naming your class AbstractItem is confusing, it implies that it is actually abstract but it is not.
Guid is a poor name for a property because it is already a Type. You have something named Guid that is an int - confusing.
I am trying to do a blog project and I am using ado.net and I have 3-tier architecture.
In one classlibrary I have classes such as User and Comments:
public class User
{
public int userID{ get; set; }
public string userName{ get; set; }
public string userPassword { get; set; }
public string userMail{ get; set; }
}
public class Comments
{
public int ID { get; set; }
public int userID{ get; set; }
public string commentHeader{ get; set; }
public string commentContent{ get; set; }
}
I want to have a userName property in the Comments class. And I decided to create an open property in the Comments class.
Because I will show in these in a UI and I want to see the UserName along with UserID; for a better understanding about whom send this comment.
How I can create the following?
public string userName
{
get
{
return //(what I have to write here)
}
}
Multiple ways to do that.
Assuming you have list of Users in your code, you can query against that list and retrieve the UserName in your property. Something like:
public string userName
{
get
{
return userList.Single(r=>r.UserID == this.UserID).UserName; // Use single
//if you are sure there's going to be a single record against a user ID
//Otherwise you may use First / FirstOrDefault
}
}
Or
you may use composition and place User object inside the Comments class.
public class Comments
{
public int ID { get; set; }
public User user { get; set; } // User object in Comments class
public string commentHeader{ get; set; }
public string commentContent{ get; set; }
}
and then in your property you can simply do:
public string userName
{
get
{
return user.UserName;
}
}
public string userName
{
get
{
return userList.FirstOrDefault(user => user.userID == userID).userName;
}
}
where userList is
List<User> userList;