Consider this Poco:
public class User
{
public int Id { get; set; }
public string Username { get; set; }
public string Fullname { get; set; }
}
Now i want to implement a follow technique where a user may follow other users so basically its self Many to Many relationship
problem is i don't know how exactly i can achieve this in Entity Framework Code-First ?
I thought of a linker Table :
public class UserFollow
{
public int Id { get; set; }
public int Follower { get; set; }
public int Following { get; set; }
public DateTime FollowDate { get; set; }
}
i want to be able to get All Followers and Following from every User Object?
This is quite simple using EF code-first as you only need the User POCO:
public class User
{
public int Id { get; set; }
public string Username { get; set; }
public string Fullname { get; set; }
public ICollection<User> FollowedUsers { get; set; }
}
The collection means that a User is related to other users.
PS: I noted you added a timestamp in your solution example. To achieve that you should still add the collection changing the generic type to whatever suits your needs.
Hope it helps.
Related
I've been trying to figure out how to do the following (although my research did not help): I have the these three classes:
public abstract class Classifier
{
public int ClassifierId { get; set; }
public string ClassifierName { get; set; }
public DateTime DateAdded { get; set; }
}
public class ManualClassifier : Classifier
{
public int ManualClassifierId { get; set; }
public string user_name { get; set; }
public string userName { get; set; }
public string firstName { get; set; }
public string lastName { get; set; }
public string email { get; set; }
public string password { get; set; }
}
public class ToolClassifier : Classifier
{
public int ToolId { get; set; }
public string ToolName { get; set; }
}
Both the ManualClassifier and ToolClassifer inherit from Classifier. I'm using EF Core to map this to a database but the question is the following: I've already searched a bit and I must make use of a descriminator which basically is an implicitly created column that will say the type of, in this case, classifier. So far so good. The issue arises when I have a property called ManualClassifierId as well as a ToolId. I want this two properties to map to the ClassifierId property. So in the table representing the entity Classifier, the ClassifierId property will either be the ManualClassifierId or the ToolId.
How can I achieve this mapping? Also, this solution would mean that both child classes would both have empty fileds in the tables (due to inheriting the three properties from the Classifier class). Is there a better solution? Perhaps just erase the Id's from both child classes a let them inherit the parent one?
Thank you in advance!
To use the same column name in both classes, you can add a Column attribute to both properties. Then they will both use that column name in the database. See ColumnAttribute(String).
Use it like this:
public class ManualClassifier : Classifier
{
[Column(Name="ClassifierId")]
public int ManualClassifierId { get; set; }
...........
}
Do the same with ToolId.
I'm trying to think of a way to store actual templates of ticket items in my Entity Framework MVC project. The thing is, I've already done a Code First migration process in the past. What I need to do is create logic in my code to allow someone to save time creating a ticket by using pre-loaded data from a template. My current inheritance model uses an abstract class (MasterTicket) which is used as the parent since to me there can be multiple categories (a Google Calendar based task, "Appointment Task" and a purely internal task, "General Task"). Here's my parent abstract class:
[Table("Ticket")]
[ModelBinder(typeof(MasterTicketBinder))]
public abstract class MasterTicket
{
[Key]
public Guid id{ get; set; }
[DatabaseGenerated(DatabaseGeneratedOption.Identity)]
public int ART { get; set; }
public DateTime openTime{ get; set; }
public DateTime? closeTime { get; set; }
private bool active = true;
public bool Active{ get => active; set => active = value; }
public string summary{ get; set; }
public string description{ get; set; }
public DateTime updateTime{ get; set; }
//TODO: Create foreign key relationship to user model
public Guid userUpdateId{ get; set; }
//TODO: Create foreign key relationship for tickets from other systems
public Guid externalAppId{ get; set; }
//TODO: Create foreign key relationship to user model
public Guid userOpenId{ get; set; }
public Guid? userCloseId { get; set; }
public Guid userOwnerId{ get; set; }
private int timesUpdated = 0;
public int TimesUpdated { get => timesUpdated; set => timesUpdated = value; }
public DateTime expectedCompletionTime{ get; set; }
public DateTime actualCompletionTime{ get; set; }
public List<MasterTicketItem> masterTicketItems{ get; set; }
public MasterTicket()
{
}
}
An here's an example of the concrete Google Calendar-based "Appointment Task" child:
[Table("AppointmentTickets")]
public class ApptTaskTicket : MasterTicket
{
public DateTime currentApptTime { get; set; }
public DateTime? endApptTime { get; set; }
public bool allDay { get; set; }
public string customerName { get; set; }
//TODO: Create foreign relationship
public Guid subjectPrsnlId { get; set; }
public string gCalEventId { get; set; }
public string customerPhone { get; set; }
public string customerEmail { get; set; }
public string preferredContactMethod { get; set; }
public List<ApptConfirmItem> apptConfirmItems { get; set; }
}
I know I can easily create a column for the MasterTicket class to indicate that it's a template, but to me I feel it's cleaner to have a separate "Template Table" if you will that will store pre-existing values that can be filled in with a form. In this case, I think I would WANT to create a duplicate class that would store said templates so that there are only several rows. What would be the best way to do this with Code First? Does someone feel I should take a different approach? Maybe DB First is a better way to go?
In case it matters, here's my DBContext for the Tickets:
// Code-Based Configuration and Dependency resolution
[DbConfigurationType(typeof(MySqlEFConfiguration))]
public class TicketDB : DbContext
{
public TicketDB(): base("AffirmativeServiceSystem.Properties.Settings.AffirmTaskManager")
{
}
public DbSet<MasterTicket> tickets { get; set; }
public DbSet<MasterTicketItem> ticketItems { get; set; }
}
I'm not sure the best way to create this kind of relation ship. I have these two entities for this example.
Person & Address
public class Person
{
public string Name { get; set; }
public virtual ICollection<PersonAddressLink> HomeAddresses { get; set; }
public virtual ICollection<PersonAddressLink> WorkAddresses { get; set; }
}
public class Address
{
public string AddressString {get; set; }
public virtual ICollection<Person> People { get; set; }
}
and a link table, needed because it contains other info.
public class PersonAddressLink
{
public Address HomeAddress { get; set; }
public Address WorkAddress { get; set; }
public int SomeOtherInt { get; set; }
public string SomeOtherString { get; set; }
}
The problem is EF doesn't know how to separate the entities on person.HomeAddresses / person.WorkAddresses. I have tried mergin HomeAddress & WorkAddresses into a single collection like this:
public virtual ICollection<PersonAddressLink> WorkAddresses { get; set; }
but it still won't work.
I'm just looking for advice on how to lay something like this out to get it working with EF Code first.
I hope that makes sense.
Thanks
Late reply but I got the mapping correct by creating the table in SQL Management studio and using the reverse engineer functionality which generated the Code First. I need to use two separate entities.
I have a problem with the table creation of EF5 Code first. I'm going to demonstrate two cases and their outputs. What I want to know what the difference between them and how I could be successful on my goal.
Case 1
public class User{
public int ID { get; set; }
public string Name { get; set; }
public ICollection<UserMessage> Messages { get; set; }
}
public class UserMessage{
public int ID { get; set; }
public string Message { get; set; }
public User CreatedBy { get; set; }
public ICollection<User> PermittedUsers {get; set;}
}
Now in this case, entity framework generates only User and UserMessage classes that are only binding to each other with UserMessage_ID in User and CreatedBy_ID in UserMessage.
The problem that I'm curious is in here. How will EF5 recognize permitted users whenever I create a new message? Is it going to duplicate the same message for each permitted users? Or what?
Case 2
public class User{
public int ID { get; set; }
public string Name { get; set; }
public ICollection<UserMessage> Messages { get; set; }
}
public class UserMessage{
public int ID { get; set; }
public string Message { get; set; }
public ICollection<User> PermittedUsers {get; set;}
}
In this case I have removed just only CreatedBy in UserMessage entity. Now EF5 generates 3 tables named : User, UserMessage, UserMessageUsers. The links between UserMessage and User is now over UserMessageUsers so that we can easily manage permitted users.
How can I add CreatedBy property into UserMessage without breaking up Case 2 ?
You can use fluent api to configurate it:
modelBuilder.Entity<UserMessage>()
.HasMany(d=>d.PermittedUsers)
.WithMany(d=>d.Messages)
.Map(c=>c.ToTable("UserMessageUsers"));
Building my project using Code First EF.
I have a User class that has, as one of its properties, List<FriendGroup> (where a FriendGroup is basically just a collection of Users, kind of like 'Circles' in Google+). FriendGroup is defined in a different file as a POCO and... here's the thing... I never said anywhere that it is a ComplexType.
But when I try to run my application I get the exception,
System.InvalidOperationException: The type 'FriendGroup' has already been configured as an entity type. It cannot be reconfigured as a complex type.
I would be grateful for any insight anyone might be able to offer on why ASP.NET decided my class is a ComplexType. Thanks in advance!
ETA: relevant bits from my model:
namespace Clade.Models
{
public class User
{
[Key]
public int userID { get; private set; }
[Required]
public Profile profile { get; set; }
[Required]
public string userName { get; set; }
...
public List<FriendGroup> friendGroups { get; set; }
...
public List<AchievementEarned> achievementsEarned { get; set; }
}
}
namespace Clade.Models
{
public class FriendGroup
{
[Key]
[HiddenInput(DisplayValue = false)]
public int friendGroupID { get; private set; }
[HiddenInput(DisplayValue = false)]
public int userID { get; set; }
[Required]
public string friendGroupName { get; set; }
public Privacy defaultPrivacy { get; set; }
[Timestamp]
public DateTime dateCreated { get; set; }
public List<User> usersInFG { get; set; }
public void UpdateMe(FriendGroup editedFG)
{
friendGroupName = editedFG.friendGroupName;
defaultPrivacy = editedFG.defaultPrivacy;
usersInFG = editedFG.usersInFG;
}
}
}
There's also EF code, repositories, etc. but none of them know anything about the inner workings of any POCO. The only thing I see here that may be problematic is that User has a List<FriendGroup> and FriendGroup has a List<User>. But nothing has ever existed that annotated FriendGroup as a ComplexType.
ETA (2): Profile is also just a POCO:
namespace Clade.Models
{
public class Profile
{
[Key]
public int profileID { get; private set; }
public User user { get; set; }
public DiscussionGroup dg { get; set; }
public string location { get; set; }
public Privacy locationPrivacy { get; set; }
public string aboutMe { get; set; }
public Privacy aboutMePrivacy { get; set; }
...
}
}
User does have Lists of a couple of ComplexType-annotated objects, but EF did not complain about those.
namespace Clade.Models
{
[ComplexType]
public class AchievementEarned
{
public Achievement achievement { get; set; }
[Timestamp]
public DateTime dateEarned { get; set; }
}
}
ETA (3): Here's the method in UserRepository where the error occurs. It happens on the line which starts with var results.
public bool Add(User newUser)
{
bool rv = false;
//check to make sure no one else has the same username first
var results = from user in Users
where user.userName.Equals(newUser.userName)
select user;
if (results.Count() == 0)
{
this.context.Users.Add(newUser);
this.Commit();
rv = true;
}
return rv;
}
You may try the following:
Use int property instead of Enum
or try to update to EF 5 beta 2 with
PM> Install-Package EntityFramework -Pre
wich much better supports enums