I am trying to simplify a process of mapping classes. For this purpose I am using AutoMapper. If no one of classes does not have a nested collection then all is great. But if someone have, I have a trouble with mapping. Collection into a class is overwriting. I found an extension AutoMapper.Collection. But it does not work for me.
I am working on a web api project, so some parts of codes here:
// Classes for mapping
public class A_Dto
{
public int Id { get; set; }
public List<A_SubItem_Dto> SubItems { get; set; }
}
public class A_SubItem_Dto
{
public int Id { get; set; }
public string Value { get; set; }
public A_Dto A_MainObject { get; set; }
}
public class A_Resource
{
public int Id { get; set; }
public List<A_SubItem_Resource> SubItems { get; set; }
}
public class A_SubItem_Resource
{
public int Id { get; set; }
public string Value { get; set; }
}
// Configure AutoMapper
public void ConfigureServices(IServiceCollection services)
{
services.AddAutoMapper(cfg => cfg.AddCollectionMappers(), typeof(Startup));
}
// Configure profile class for mapping
public class AutoMapping : Profile
{
CreateMap<A_Dto, A_Resource>().ReverseMap()
.ForMember(m => m.Id, opt => opt.Ignore());
CreateMap<A_SubItem_Dto, A_SubItem_Resource>().ReverseMap()
.EqualityComparison((sir, si) => sir.Id == si.Id);
}
// Controller action with simple test
public async Task<IActionResult> Put(/*...*/)
{
// Test
var aDto = new A_Dto()
{
Id = 7,
SubItems = new List<A_SubItem_Dto>()
{
new A_SubItem_Dto() { Id = 2, Value = "_2_" },
new A_SubItem_Dto() { Id = 9, Value = "_9_" }
}
};
var aResource = new A_Resource()
{
Id = 7,
SubItems = new List<A_SubItem_Resource>()
{
new A_SubItem_Resource() { Id = 2, Value = "_222222_" }
}
};
_mapper.Map(aResource, aDto);
}
In result aDto object contains new collection with one element of aResource.SubItems
Could you tell me please, what I am doing wrong?
Related
i have following entities..
public class Paper
{
public int Id { get; set; }
public string PaperCode { get; set; }
...
}
public class MCQPaper : Paper
{
public ICollection<MCQQuestion> Questions { get; set; }
}
public class MCQQuestion : Question
{
public int MCQPaperId { get; set; }
public MCQPaper MCQPaper { get; set; }
public int? MCQOptionId { get; set; }
[ForeignKey("MCQOptionId")]
public MCQOption TrueAnswer { get; set; }
public ICollection<MCQOption> MCQOptions { get; set; }
}
public class MCQOption
{
public int Id { get; set; }
public string OptionText { get; set; }
}
and i am trying to fetch MCQPaper based on unique papercode but it always gives me empty collection of Questions
here is my Query inside Repository..
public MCQPaper GetByPaperCode(string paperCode)
{
var ans = AppDbContext.MCQPapers
.Where(paper => paper.PaperCode.Equals(paperCode))
//.Include(paper => paper.Questions)
// .ThenInclude(que => que.MCQOptions)
.Include(paper => paper.Questions)
.ThenInclude(que => que.MCQPaper)
//.Include(paper => paper.Questions)
// .ThenInclude(que => que.TrueAnswer)
.FirstOrDefault();
return ans;
}
here i have tried various combinations of include() and theninclude() but none of them work for me
and lastly ignore grammer mistakes if any
thankyou in advance
after going threw comments and searching on google i have found solution
using two queries this problem can be solved because here i have circular dependency between MCQQuestion and MCQOption
so solution is ....
public MCQPaper GetByPaperCode(string paperCode)
{
using var transaction = AppDbContext.Database.BeginTransaction();
MCQPaper ans = new MCQPaper();
try
{
ans = AppDbContext.MCQPapers
.FirstOrDefault(paper => paper.PaperCode.Equals(paperCode));
var questions = AppDbContext.MCQQuestions
.Include(que => que.MCQOptions)
.Where(que => que.MCQPaperId == ans.Id);
ans.Questions = questions.ToList();
transaction.Commit();
}
catch (Exception)
{
transaction.Rollback();
}
return ans;
}
Lets say I would implement a Table Per Hierarchy for a class where I would store subclasses of this type distinguished by a discriminator (~ 5 types).
Some subclasses will have their own ICollections and some wont, so this will not be specified in the superclass. Im currenly only able to fetch the data that is directly stored in the table but unable to fetch the collection of this subclass (length of collection will be 0)
Any thoughts on how I would be able to fill in this list when I fetch this specific subclass (with specific discriminator) object from the database?
Here is a fully working sample console project, that demonstrates this approach:
using System.Collections.Generic;
using System.Diagnostics;
using System.Linq;
using Microsoft.EntityFrameworkCore;
using Microsoft.Extensions.Logging;
namespace IssueConsoleTemplate
{
public class IceCream
{
public int IceCreamId { get; set; }
public string Name { get; set; }
}
public class IceCreamAsDrink : IceCream
{
public string DrinkName { get; set; }
}
public class IceCreamWithToppings : IceCream
{
public ICollection<Topping> Toppings { get; set; } = new HashSet<Topping>();
}
public class Topping
{
public int ToppingId { get; set; }
public string Name { get; set; }
public int IceCreamWithToppingsIceCreamId { get; set; } // <-- use this exact
// name or use the
// Fluent API
public IceCreamWithToppings IceCreamWithToppings { get; set; }
}
public class Context : DbContext
{
public DbSet<IceCream> IceCreams { get; set; }
public DbSet<IceCreamAsDrink> IceCreamsAsDrink { get; set; }
public DbSet<IceCreamWithToppings> IceCreamsWithToppings { get; set; }
public DbSet<Topping> Toppings { get; set; }
protected override void OnConfiguring(DbContextOptionsBuilder optionsBuilder)
{
optionsBuilder
.UseSqlServer(
#"Data Source=.\MSSQL14;Integrated Security=SSPI;Initial Catalog=So63087805")
.UseLoggerFactory(
LoggerFactory.Create(
b => b
.AddConsole()
.AddFilter(level => level >= LogLevel.Information)))
.EnableSensitiveDataLogging()
.EnableDetailedErrors();
}
protected override void OnModelCreating(ModelBuilder modelBuilder)
{
modelBuilder.Entity<IceCreamWithToppings>()
.HasMany(e => e.Toppings)
.WithOne(e => e.IceCreamWithToppings)
.HasForeignKey(e => e.IceCreamWithToppingsIceCreamId);
modelBuilder.Entity<IceCream>().HasData(
new IceCream
{
IceCreamId = 1,
Name = "Basic Vanilla"
});
modelBuilder.Entity<IceCreamAsDrink>().HasData(
new IceCreamAsDrink
{
IceCreamId = 2,
Name = "Vanilla Ice Coffee",
DrinkName = "Coffee"
});
modelBuilder.Entity<IceCreamWithToppings>().HasData(
new IceCreamWithToppings
{
IceCreamId = 3,
Name = "Vanilla With Sprinkles"
});
modelBuilder.Entity<Topping>().HasData(
new Topping
{
ToppingId = 1,
Name = "Chocolate Sprinkles",
IceCreamWithToppingsIceCreamId = 3
},
new Topping
{
ToppingId = 2,
Name = "Whipped Cream",
IceCreamWithToppingsIceCreamId = 3
});
}
}
internal static class Program
{
private static void Main()
{
using var context = new Context();
context.Database.EnsureDeleted();
context.Database.EnsureCreated();
var allIceCreams = context.IceCreams
.OrderBy(i => i.IceCreamId)
.ToList();
var iceCreamsAsDrink = context.IceCreamsAsDrink
.ToList();
var iceCreamsWithToppings = context.IceCreamsWithToppings
.Include(i => i.Toppings)
.ToList();
Debug.Assert(allIceCreams.Count == 3);
Debug.Assert(iceCreamsAsDrink.Count == 1);
Debug.Assert(iceCreamsWithToppings.Count == 1);
Debug.Assert(iceCreamsWithToppings[0].Toppings.Count == 2);
}
}
}
If you want to use conventions for the foreign key between Topping and IceCreamWithToppings, then the foreign key needs to be named <DerivedType><PrimaryKeyOnBaseType>, so IceCreamWithToppingsIceCreamId in this case.
Alternatively, just define the relationship using the Fluent API:
public class Topping
{
public int ToppingId { get; set; }
public string Name { get; set; }
public int MyForeignKeyToIceCream { get; set; } // <-- non-convention name
public IceCreamWithToppings IceCreamWithToppings { get; set; }
}
public class Context : DbContext
{
protected override void OnModelCreating(ModelBuilder modelBuilder)
{
modelBuilder.Entity<IceCreamWithToppings>()
.HasMany(e => e.Toppings)
.WithOne(e => e.IceCreamWithToppings)
.HasForeignKey(e => e.MyForeignKeyToIceCream);
}
}
I have just started using AutoMapper on an asp net core project and I'm trying to map an object that has a collection of an object that also has a collection of an object to an entity.
The source
public class MyClass
{
public List<MyCollection> MyCollections { get; set; }
}
public class MyCollection
{
public int CollectionId { get; set; }
public List<Description> Descriptions { get; set; }
}
public class Description
{
public int DescriptionId { get; set; }
public string Text { get; set; }
}
The destination
public class DescriptionToCollection
{
public int DescriptionId { get; set; }
public int CollectionId { get; set; }
}
I've played around with ConvertUsing thinking something like this, but I can't make it work.
CreateMap<MyClass, List<DescriptionToCollection>>()
.ConvertUsing(source => source.MyCollections.Select(x =>x.Description.Select(y=> new DescriptionToCollection{ DescriptionId=y.DescriptionId,CollectionId=x.CollectionId}).ToList()
));
Searching AutoMappers docs and the internet, I couldn't find anything similar to my problem.
Any help is highly appreciated.
Besides a typo in your example code, you almost had it. Because you aren't mapping 1:1 at the top level, you need to flatten somewhere, and you do that using SelectMany, moving the ToList call appropriately.
CreateMap<MyClass, List<DescriptionToCollection>>()
.ConvertUsing(source => source.MyCollections.SelectMany(x => // SelectMany to flatten
x.Descriptions.Select(y =>
new DescriptionToCollection
{
DescriptionId = y.DescriptionId,
CollectionId = x.CollectionId
}
) // ToList used to be here
).ToList()
);
Try to implement ITypeConverter, follow the example code:
Your Classes
public class Class1
{
public List<Class2> class2 { get; set; }
}
public class Class2
{
public int CollectionId { get; set; }
public List<Class3> class3 { get; set; }
}
public class Class3
{
public int DescriptionId { get; set; }
public string Text { get; set; }
}
public class ClassDto
{
public int DescriptionId { get; set; }
public int CollectionId { get; set; }
}
The custom map
public class ClassCustomMap : ITypeConverter<Class1, List<ClassDto>>
{
public List<ClassDto> Convert(Class1 source, List<ClassDto> destination, ResolutionContext context)
{
var classDtoList = new List<ClassDto>();
foreach (var item in source.class2)
{
var collectionID = item.CollectionId;
foreach (var obj in item.class3)
{
var classDto = new ClassDto();
classDto.CollectionId = collectionID;
classDto.DescriptionId = obj.DescriptionId;
classDtoList.Add(classDto);
}
}
return classDtoList;
}
}
The mapping declaration
CreateMap<Class1, List<ClassDto>>().ConvertUsing<ClassCustomMap>();
How to use it
var class2 = new Class2();
class2.CollectionId = 2;
var class3 = new Class3();
class3.DescriptionId = 1;
class3.Text = "test";
class2.class3 = new System.Collections.Generic.List<Class3>() { class3 };
var class1 = new Class1();
class1.class2 = new System.Collections.Generic.List<Class2>() { class2 };
var result = mapper.Map<List<ClassDto>>(class1);
For clarity and to simplify I have used explicit cycles, if you want you can optimize the conversion function using LinQ and Lambda
You are missing the purpose of auto-mapper.
It should be used for transforming an input object of one type into an output object of a different type.
And you wanted to create a map from MyClass type to List - this should be treated as projection.
You can achieve that using LINQ (for example as a extension method on MyClass):
public static class MyClassExtension
{
public static List<DescriptionToCollection> ToDescriptionToCollection(this MyClass value)
{
return value.MyCollections.SelectMany(mc => mc.Descriptions.Select(d => new DescriptionToCollection()
{
CollectionId = mc.CollectionId,
DescriptionId = d.DescriptionId
})).ToList();
}
}
I have two sets of objects
Objects that I use in C# client application:
public class EmployeeClient
{
public int Id { get; set; }
public int DepartmentId { get; set; }
public string FirstName { get; set; }
public string LastName { get; set; }
public string MiddleName { get; set; }
}
public class DepartmentClient
{
public int Id { get; set; }
public string Name { get; set; }
}
public class OrganizationClient
{
public int Id { get; set; }
public string Name { get; set; }
public List<DepartmentClient> Departments { get; set; }
public List<EmployeeClient> Employees { get; set; }
}
And DTOs:
public class EmployeeDto
{
public int Id { get; set; }
public string FirstName { get; set; }
public string LastName { get; set; }
public string MiddleName { get; set; }
}
public class DepartmentDto
{
public int Id { get; set; }
public string Name { get; set; }
public List<EmployeeDto> Employees { get; set; }
}
public class OrganizationDto
{
public int Id { get; set; }
public string Name { get; set; }
public List<DepartmentDto> Departments { get; set; }
}
I use AutoMapper and I need to configure mapping Client -> DTOs and DTOs -> Client.
I implemented mapping DTOs->Client like this:
public class DtoToClientMappingProfile: Profile
{
public DtoToClientMappingProfile()
{
CreateMap<EmployeeDto, EmployeeClient>();
CreateMap<DepartmentDto, DepartmentClient>();
CreateMap<OrganizationDto, OrganizationClient>()
.ForMember(dest => dest.Employees, opt => opt.ResolveUsing(src => src.Departments.SelectMany(d => d.Employees)))
.AfterMap(AfterMap);
}
private void AfterMap(OrganizationDto dto, OrganizationClient client)
{
foreach (var department in dto.Departments)
{
foreach (var employee in department.Employees)
{
var clientEmployee = client.Employees.First(e => e.Id == employee.Id);
clientEmployee.DepartmentId = department.Id;
}
}
}
}
It is not universal solution, but is works for me.
I've found only one option how mapping Client->DTOs could be implemented:
public class ClientToDtosMappingProfile : Profile
{
public ClientToDtosMappingProfile()
{
CreateMap<EmployeeClient, EmployeeDto>();
CreateMap<DepartmentClient, DepartmentDto>();
CreateMap<OrganizationClient, OrganizationDto>()
.AfterMap(AfterMap);
}
private void AfterMap(OrganizationClient client, OrganizationDto dto)
{
foreach (var employee in client.Employees)
{
var departmentDto = dto.Departments.First(d => d.Id == employee.DepartmentId);
if (departmentDto.Employees == null)
{
departmentDto.Employees = new List<EmployeeDto>();
}
var configuration = (IConfigurationProvider)new MapperConfiguration(cfg =>
{
cfg.AddProfiles(typeof(ClientToDtosMappingProfile));
});
var mapper = (IMapper)new Mapper(configuration);
var employeeDto = mapper.Map<EmployeeDto>(employee);
departmentDto.Employees.Add(employeeDto);
}
}
}
It works, but I do not like this solution because I should create instance of new Mapper every time I map objects. In my real code Employee has a lot of nested elements and mapping is configured in multiple profiles.
Any ideas how it could be implemented better?
I made my code a bit better using ResolutionContext. It allows not to create mappers in AfterMap function.
DtoToClientMappingProfile:
public class DtoToClientMappingProfile: Profile
{
public DtoToClientMappingProfile()
{
CreateMap<EmployeeDto, EmployeeClient>();
CreateMap<DepartmentDto, DepartmentClient>();
CreateMap<OrganizationDto, OrganizationClient>()
.ForMember(dest => dest.Employees, opt => opt.Ignore())
.AfterMap(AfterMap);
}
private void AfterMap(OrganizationDto dto, OrganizationClient client, ResolutionContext resolutionContext)
{
if (dto.Departments == null)
{
return;
}
client.Departments = new List<DepartmentClient>();
foreach (var department in dto.Departments)
{
var departmentClient = resolutionContext.Mapper.Map<DepartmentClient>(department);
client.Departments.Add(departmentClient);
if (department.Employees == null)
{
continue;
}
if (client.Employees == null)
{
client.Employees = new List<EmployeeClient>();
}
foreach (var employee in department.Employees)
{
var employeeClient = resolutionContext.Mapper.Map<EmployeeClient>(employee);
employeeClient.DepartmentId = department.Id;
client.Employees.Add(employeeClient);
}
}
}
ClientToDtosMappingProfile:
public class ClientToDtosMappingProfile : Profile
{
public ClientToDtosMappingProfile()
{
CreateMap<EmployeeClient, EmployeeDto>();
CreateMap<DepartmentClient, DepartmentDto>();
CreateMap<OrganizationClient, OrganizationDto>()
.AfterMap(AfterMap);
}
private void AfterMap(OrganizationClient client, OrganizationDto dto, ResolutionContext resolutionContext)
{
if (client.Employees == null)
{
return;
}
foreach (var employee in client.Employees)
{
var departmentDto = dto.Departments.First(d => d.Id == employee.DepartmentId);
if (departmentDto.Employees == null)
{
departmentDto.Employees = new List<EmployeeDto>();
}
var employeeDto = resolutionContext.Mapper.Map<EmployeeDto>(employee);
departmentDto.Employees.Add(employeeDto);
}
}
}
If you call AssertConfigurationIsValid, AM will complain about what it doesn't know how to map.
The problem seems to be that you don't have the information needed to fill the destination object in the source object.
You will need to add a resolver for each property AM complains about, like the ResolveUsing you already have, for example.
You also need to pass the extra information that's needed.
The result may not look good eventually because AM cannot rely on uniform objects to do its job, you have to tell it what to do.
Another way to go about it is to do the high level mapping in your own code and rely on AM only when the mapping is simple enough so AM can do it by itself. The more you customize AM, the less value you get from it.
Say I have this simple entity:
public class Person
{
public int PersonID { get; set; }
public string Name { get; set; }
}
The entity framework can infer by convention that the PersonID field is the primary key. However, if I give the model builder this class:
public class PersonCfg : EntityTypeConfiguration<Person>
{
public PersonCfg()
{
ToTable("Person", "Person");
HasKey(p => p.PersonID);
}
}
Would that improve startup performance? My thought was it might allow EF to do less reflecting and startup the app faster but I don't know how it works behind the scenes to know if it has any impact.
To test this, you can use the DbModelBuilder class to build the model yourself and track the speed of the "Compile" step.
Here's my example code (LinqPad script):
void Main()
{
// Initialize the overall system, but don't count the result.
BuildC();
DateTime startDateA = DateTime.Now;
BuildA();
DateTime.Now.Subtract(startDateA).TotalMilliseconds.Dump("A");
DateTime startDateB = DateTime.Now;
BuildB();
DateTime.Now.Subtract(startDateB).TotalMilliseconds.Dump("B");
}
public class PersonA
{
public int PersonAId { get; set; }
public string Name { get; set; }
}
private void BuildA()
{
var builder = new DbModelBuilder();
builder.Entity<PersonA>();
var model = builder.Build(new DbProviderInfo("System.Data.SqlClient", "2008"));
model.Compile();
}
public class PersonB
{
public int PersonBId { get; set; }
public string Name { get; set; }
}
private void BuildB()
{
var builder = new DbModelBuilder();
builder.Conventions.Remove<IdKeyDiscoveryConvention>();
builder.Entity<PersonB>()
.HasKey(p => p.PersonBId);
var model = builder.Build(new DbProviderInfo("System.Data.SqlClient", "2008"));
model.Compile();
}
public class PersonC
{
public int PersonCId { get; set; }
public string Name { get; set; }
}
private void BuildC()
{
var builder = new DbModelBuilder();
builder.Entity<PersonC>()
.HasKey(p => p.PersonCId);
var model = builder.Build(new DbProviderInfo("System.Data.SqlClient", "2008"));
model.Compile();
}
I get the result of 2.0004ms to 2.0009ms. Curiously, removing conventions made the operation take longer.