Have class Books and there i should implement two foreign tables. Comments and Rating. This is the class:
public class Books
{
public Books()
{
CommentsList = new List<Comments>();
}
public Books()
{
RatingList = new List<Rating>();
}
public virtual int Id { get; set; }
public virtual string Title { get; set; }
public virtual string Category { get; set; }
public virtual string ISBN { get; set; }
public virtual string Description { get; set; }
public virtual string Image { get; set; }
// public virtual int CategoryId { get; set; }
public virtual Categories Categories { get; set; }
public virtual IList<Comments> CommentsList { get; set; }
public virtual IList<Rating> RatingList { get; set; }
public virtual void AddComment(Comments comm)
{
comm.Books = this;
CommentsList.Add(comm);
}
public virtual void AddRating(Rating rating)
{
rating.Books = this;
RatingList.Add(rating);
}
}
It gives an error
Error 2 already defines a member called 'Books' with the same
parameter types
How to solve this to have possibility to add comments and rating to a book ?
You have the same constructor two times. I guess you're using Entity Framework and if I recall correctly, you want to change those ILists to ICollections to use the Entity Framework lazy-loading features.
Change
public class Books
{
public Books()
{
CommentsList = new List<Comments>();
}
public Books()
{
RatingList = new List<Rating>();
}
}
To :
public class Books
{
public Books()
{
CommentsList = new List<Comments>();
RatingList = new List<Rating>();
}
}
You simply can't have two constructors that have the same signature. You should consider using a builder pattern instead.
You would typically hide the constructors (make them private) and instead expose static methods like CreateFromComments and CreateFromRatings.
private Books() { }
public static Books CreateFromComments()
{
var ret = new Books();
ret.CommentsList = new List<Comments>();
return ret;
}
public static Books CreateFromRatings()
{
var ret = new Books();
ret.RatingsList = new List<Ratings>();
return ret;
}
may be you can pass a boolean param to set the list to initialize...
public Books(bool comments)
{
if (comments)
CommentsList = new List<Comments>();
else
RatingList = new List<Rating>();
}
Related
I reposted question on codereview but can not delete this question couse already answer here.
I have some classes:
public abstract class House
{
public string Name { set; get;}
public SomeClass Property1 { set; get;}
public OtherClass Property2 { set; get;}
}
public class WoodenHouse:House
{
public string WoodType { set; get;}
public int WoodAge { set; get;}
}
public class StoneHouse:House
{
public string StoneType { set; get;}
}
And trying to create Factory Method pattern for this:
abstract class Creator
{
public abstract HouseInfo Info { get; set; }
public Creator()
{
}
public abstract House FactoryMethod();
}
class WoodenHouseCreator : Creator
{
public override HouseInfo Info { get; set; }
public WoodenHouseCreator(WoodenHouseInfo info)
{
Info = info;
}
public override House FactoryMethod()
{
var info = Info as WoodenHouseInfo;
var woodenHouse = new WoodenHouse();
woodenHouse.Name = info.Name;
woodenHouse.Floors = info.Floors;
woodenHouse.RoofType = info.RoofType;
woodenHouse.WoodType = info.WoodType;
woodenHouse.WoodAge = info.WoodAge;
return woodenHouse;
}
}
class StoneHouseCreator : Creator
{
public override HouseInfo Info { get; set; }
public StoneHouseCreator(StoneHouseInfo info)
{
Info = info;
}
public override House FactoryMethod()
{
var info = Info as StoneHouseInfo;
var stoneHouse = new StoneHouse();
stoneHouse.Name = info.Name;
stoneHouse.Floors = info.Floors;
stoneHouse.RoofType = info.RoofType;
stoneHouse.StoneType = info.StoneType;
return stoneHouse;
}
}
Here are the classes what contain information to create ahouse:
class HouseInfo
{
public string Name { set; get; }
public int Floors { set; get; }
public string RoofType { set; get; }
}
class WoodenHouseInfo : HouseInfo
{
public string WoodType { set; get; }
public int WoodAge { set; get; }
}
class StoneHouseInfo : HouseInfo
{
public string StoneType { set; get; }
}
And Usage:
var houseInfo = new WoodenHouseInfo
{
Name = "HouseName",
Floors = 2,
RoofType = "Triangle",
WoodType = "Pine",
WoodAge = 100
};
House house;
if(houseInfo is WoodenHouseInfo)
{
var creator = new WoodenHouseCreator(houseInfo);
house = creator.FactoryMethod();
Console.Write((house as WoodenHouse).WoodAge);
}
Full code fiddle.
My problem is how to handle code duplication. I mean there is a lot of lines that fills base House object properties. How can I write that code only once?
Or I should not to use Factory Method?
Currently your factories instantiate the new objects and then fill in all of their properties with the right values. You could split instantiation from property value assignment. Your StoneHouseCreator could instantiate a StoneHouse, use a HousePopulator that populates the values that all objects of type House have in common, and then the StoneHouseCreator could populate the rest of the values that are exclusive to a StoneHouse. That same HousePopulator could also be used by your WoodenHouseCreator, which would then proceed to populate the WoodenHouse-specific properties.
If you want to philosophise about this at a higher level, these are the problems that we run into because of inheritance. Factories, that is the logical separation of object use from object creation, are more naturally suited to cases where you use composition over inheritance. If you are interested more in this, I would recommend reading this excellent article on the topic.
I have these:
public class FamilyHead
{
public Guid HeadId { get; set; }
public string Name { get; set; }
}
public class Citizen
{
public Guid Id { get; set; }
public string Name { get; set; }
public short Age { get; set; }
// more properties
[ForeignKey("FamilyHead")]
public Guid HeadId { get; set; }
public virtual FamilyHead FamilyHead { get; set; }
}
public class CitizenDTO
{
public Guid Id { get; set; }
public string Name { get; set; }
public short Age { get; set; }
public Guid HeadId
public string HeadName { get; set; }
}
I can manually map it via extension method if it is a single instance:
public static CitizenDTO ToDTO(this Citizen citizen)
{
if (citizen == null) return null;
return new CitizenDTO {
Id = citizen.Id,
Name = citizen.Name,
HeadId = citizen.HeadId,
HeadName = citizen.FamilyHead.Name
}
}
var dto = aCitizen.ToDTO();
But how to map a list of citizens? I think Select() might do the work but I only know how to do it if the model and the dto have a same structure. Like this example:
IEnumerable<int> integers = new List<int>() { 1, 2, 3, 4, 5 };
IEnumerable<string> strings = integers.Select(i => i.ToString());
So how to map a list of it?
You can use Linq Select() as you used for string in your question, no need to write long extension method
IEnumerable<CitizenDTO> dto = citizens.Select(x => x.ToDTO());
I found the answer before finishing my question. Just iterate through the list and add mapped DTO to it. Silly me
// Extension method
public static IEnumerable<CitizenDTO> ToDTO(this IEnumerable<Citizen> citizens)
{
if (citizen == null) return null;
var dto = new List<CitizenDTO>();
foreach(var citizen in citizens) {
dto.Add(citizen.ToDTO());
}
return dto;
}
// How to use
IEnumerable<CitizenDTO> result = listOfCitizens.ToDTO();
I chose to put a complete example of my code in order to demonstrate what I exactly need. Briefly, what I would like to do, is to get a generic code in public override int SaveChanges() that could work to all entities that implements a translation rather than write a one-by-one.
ENTITIES
public partial class EntityOne
{
public long EntityOneId { get; set; }
public string SomeProperty { get; set; }
public virtual ICollection<EntityOneTranslation> EntityOneTranslations { get; set; }
public EntityOne()
{
this.EntityOneTranslations = new HashSet<EntityOneTranslation>();
}
}
public class EntityOneTranslation : EntityTranslation<long, EntityOne>
{
public string LocalizedEntityOneProp1 { get; set; }
public string LocalizedEntityOneProp1 { get; set; }
}
public partial class EntityTwo
{
public long EntityTwoId { get; set; }
public string SomeProperty { get; set; }
public virtual ICollection<EntityTwoTranslation> EntityTwoTranslations { get; set; }
public EntityTwo()
{
this.EntityTwoTranslations = new HashSet<EntityTwoTranslation>();
}
}
public class EntityTwoTranslation : EntityTranslation<long, EntityTwo>
{
public string LocalizedEntityTwoProp1 { get; set; }
public string LocalizedEntityTwoProp2 { get; set; }
}
public class EntityTranslation<TEntityKey, TEntity> : ILanguage
{
[Key, Column(Order = 0), ForeignKey("Entity")]
public TEntityKey EntityKey { get; set; }
[Key, Column(Order = 1), ForeignKey("Language")]
public long LanguageId { get; set; }
public virtual TEntity Entity { get; set; }
public virtual Language Language { get; set; }
}
INTERFACE
public interface ILanguage
{
long LanguageId { get; set; }
}
Here is the target
How would I get the entity navigation property using reflection/or something in order to reuse my code that could work too all entities that has a translation property collection?
I already tried to ask the same thing from 2 other posts, but I didn't give all the info. I guess that's why nobody could give me the expected answer.
Adding new entries over entity navigation property collection
Cast PropertyInfo to Collection
SAVE CHANGES OVERRIDE
public override int SaveChanges()
{
foreach (var entityOneEntry in ChangeTracker.Entries<EntityOne>())
{
if (entityOneEntry.State == EntityState.Added)
{
//Get entity localized properties values of current language.
var currentLanguageEntry = entityOneEntry.Entity.EntityOneTranslations.FirstOrDefault();
var localizedEntityOneProp1 = currentLanguageEntry.LocalizedEntityOneProp1;
var localizedEntityOneProp2 = currentLanguageEntry.LocalizedEntityOneProp2;
//Get all languages but the current one.
var languages = Language.Where(l => l.LanguageId != currentCulture.Key);
//Add missing translations copying the same values.
foreach (var language in languages)
entityOneEntry.Entity.EntityOneTranslations.Add(new EntityOne()
{
LanguageId = language.LanguageId,
LocalizedEntityOneProp1 = localizedEntityOneProp1,
LocalizedEntityOneProp2 = localizedEntityOneProp2
});
}
}
foreach (var entityOneEntry in ChangeTracker.Entries<EntityTwo>())
{
if (entityOneEntry.State == EntityState.Added)
{
//Get entity localized properties values of current language.
var currentLanguageEntry = entityOneEntry.Entity.EntityTwoTranslations.FirstOrDefault();
var localizedEntityTwoProp1 = currentLanguageEntry.LocalizedEntityTwoProp1;
var localizedEntityTwoProp2 = currentLanguageEntry.LocalizedEntityTwoProp2;
//Get all languages but the current one.
var languages = Language.Where(l => l.LanguageId != currentCulture.Key);
//Add missing translations copying the same values.
foreach (var language in languages)
entityOneEntry.Entity.EntityTwoTranslations.Add(new EntityTwo()
{
LanguageId = language.LanguageId,
LocalizedEntityTwoProp1 = localizedEntityTwoProp1,
LocalizedEntityTwoProp2 = localizedEntityTwoProp2
});
}
}
}
I am trying to list some food items with a controller. I use Repository pattern with UnitOfWork for the data in another assembly and referenced it in a BaseApiController. The Data property is my UnitOfWork instance.
var result = Data.Food
.FindAll()
.Select(FoodItemViewModel.Create);
return result;
and here is my ViewModel:
public static Expression<Func<FoodItem, FoodItemViewModel>> Create
{
get
{
return fi => new FoodItemViewModel
{
Id = fi.Id,
Description = fi.Description,
DiaryEntries = fi.DiaryEntries
.Select(s => new DiaryEntityViewModel()
{
Id = s.Id,
Quantity = s.Quantity
}
};
}
}
But all I get is:
"The specified type member 'DiaryEntries' is not supported in LINQ to
Entities. Only initializers, entity members, and entity navigation
properties are supported."
My DiaryEntries member in the ViewModel is
IEnumerable<DiaryEntityViewModel>
and my DiaryEntries member in the Data instance is
IRepository<DiaryEntry>
and DiaryEntry is my model class
and here is my FoodItem model class:
public class FoodItem
{
private IEnumerable<Measure> measures;
private IEnumerable<DiaryEntry> diaryEntries;
public FoodItem()
{
this.measures = new HashSet<Measure>();
this.diaryEntries = new HashSet<DiaryEntry>();
}
public int Id { get; set; }
public string Description { get; set; }
public virtual IEnumerable<DiaryEntry> DiaryEntries
{
get
{
return this.diaryEntries;
}
set
{
this.diaryEntries = value;
}
}
public virtual IEnumerable<Measure> Measures
{
get
{
return this.measures;
}
set
{
this.measures = value;
}
}
}
Change you FoodItem class to the one below, IEnumerable<T> is not supported as a type for a navigation collection :
public class FoodItem
{
public FoodItem()
{
this.Measures = new HashSet<Measure>();
this.DiaryEntries = new HashSet<DiaryEntry>();
}
public int Id { get; set; }
public string Description { get; set; }
public virtual ICollection<DiaryEntry> DiaryEntries
{
get;
set;
}
public virtual ICollection<Measure> Measures
{
get;
set;
}
}
I am developing a MVC Project with Entity framework and i have a category table like this :
public partial class Categories
{
public Categories()
{
this.Categories1 = new HashSet<Categories>();
}
public int CategoryId { get; set; }
public string CategoryName { get; set; }
public Nullable<int> RelatedCategoryId { get; set; }
public virtual ICollection<Categories> Categories1 { get; set; } //Children
public virtual Categories Categories2 { get; set; } //Parent
}
When i get table data with EF, it gives me the object i want. Parents with children.
class Program
{
static Entities db = new Entities();
static void Main(string[] args)
{
List<Categories> categories = db.Categories.Where(item => item.RelatedId == null).ToList();
}
}
With relatedId == null part, i get the main categories which has no parent.
There is no problem this far. But i want to cast categories object which ef returned to another class which is :
public class NewCategories
{
public int Id { get; set; }
public string Name { get; set; }
private List<NewCategories> _subCategories;
public NewCategories()
{
_subCategories= new List<NewCategories>();
}
public List<NewCategories> SubCategories { get { return _subCategories; } }
}
And i want new List<NewCategories> newCategories object.
How can i accomplish that?
Thanks.
I think you have to create a recursive method to convert Categories to NewCategories, something like this (I'm not sure if it works, but it's worth trying):
public NewCategories ConvertToNewCategories(Categories cat){
NewCategories nc = new NewCategories {Id = cat.CategoryId, Name = cat.CategoryName};
nc.SubCategories.AddRange(cat.Categories1.Select(c=>ConvertToNewCategories(c)));
return nc;
}
//Then
List<NewCategories> categories = db.Categories.Where(item => item.RelatedId == null)
.Select(item=>ConvertToNewCategories(item))
.ToList();