Skip to main content

Fluent mapping approach for EF Core

With the first release of EF Core, there wasn't any proper approach of fluent mapping of entities, in an easy manner for enterprises application where a lot of entities needs to be involved. You might have ended up with nasty or repeated codes.

At that time only way was to compose mapping based on ModelBuilder and by using inline fluent mapping codes. Like in newer version EF Core 2.0 there had been a new release of IEntityTypeConfiguration for the creation of mapping based on single entity and could be registered with ApplyConfiguration by passing a new instance of IEntityTypeConfiguration object. https://docs.microsoft.com/en-us/ef/core/what-is-new (Self-contained type configuration for code first)
This is really good for big application as we can separate mappings based on each entity.

In this article, we would see how to achieve similar functionality in EF Core 1.0 and this implementation is a bit cleaner than 2.0 built-in classes. So, in both of versions, this could be used with minimum effort.

Steps/approach taken to achieve same.


  1. A base class which would have certain constraints and common functionality to take care of certain mappings.
  2. Sample mapping class based on base class for actual fluent mapping implementations.
  3. Application level fluent mapping with a helper method to create mappings generically by passing entity and associated mapping class.
  4. Registration of fluent mappings in application DbContext class by just creating an object of global fluent mapping.

Base class implementation for each Fluent mapping classes

I like to have schema name for each table so I have included parameterized constructor for accepting model name and schema name.

The other optional element I have included is to have common Primary Key Name with Identity field based on interface IPrimaryKey<int>. This allows me to have the same name for all Primary Keys and common mapping codes so that I do not have to repeat all over again.
NOTE:  This is optional you can remove InitPrimaryKey function if you do not need.

 /// <summary>  
 /// Entity builder base class for fluent mapping.  
 /// </summary>  
 /// <typeparam name="TModel">The type of the model.</typeparam>  
 internal abstract class EntityTypeBuilderBase<TModel>  
   where TModel : class  
 {  
   /// <summary>  
   /// The model name  
   /// </summary>  
   private readonly string ModelName;  
   /// <summary>  
   /// The model schema  
   /// </summary>  
   private readonly string ModelSchema;  
   /// <summary>  
   /// Initializes a new instance of the <see cref="EntityTypeBuilderBase{TModel}"/> class.  
   /// </summary>  
   /// <param name="modelName">Name of the model.</param>  
   /// <param name="modelSchema">The model schema.</param>  
   /// <exception cref="ArgumentNullException">  
   /// modelName  
   /// or  
   /// modelName  
   /// </exception>  
   protected EntityTypeBuilderBase(string modelName, string modelSchema)  
   {  
     if (IsNullOrEmpty(modelName))  
     {  
       throw new ArgumentNullException(nameof(modelName));  
     }  
     if (IsNullOrEmpty(modelSchema))  
     {  
       throw new ArgumentNullException(nameof(modelName));  
     }  
     ModelName = modelName;  
     ModelSchema = modelSchema;  
   }  
   /// <summary>  
   /// Initializes the specified builder.  
   /// </summary>  
   /// <param name="builder">The builder.</param>  
   public void Init(EntityTypeBuilder<TModel> builder)  
   {  
     InitPrimaryKey(builder);  
     builder.ToTable(ModelName, ModelSchema);  
   }  
   /// <summary>  
   /// Fluent mapping for the model.  
   /// </summary>  
   /// <param name="builder">The entity DB builder.</param>  
   public abstract void Map(EntityTypeBuilder<TModel> builder);  
   /// <summary>  
   /// Initializes the primary key.  
   /// </summary>  
   /// <param name="entityTypeBuilder">The entity type builder.</param>  
   private static void InitPrimaryKey(EntityTypeBuilder<TModel> entityTypeBuilder)  
   {  
     var primaryKeyBuilder = entityTypeBuilder as EntityTypeBuilder<IPrimaryKey<int>>;  
     if (primaryKeyBuilder != null)  
     {  
       primaryKeyBuilder.HasKey(m => m.Id);  
       primaryKeyBuilder.Property(m => m.Id).ValueGeneratedOnAdd();  
     }  
   }  
 }

The Map abstract function is important since this is going to be used in each Fluent Mapping classes.

Sample entity mapping class

Suppose we have an entity called LookupCountry. The fluent mapping based on sample model.

 /// <summary>  
 /// Fluent mapping for <see cref="LookupCountry"/> entity.  
 /// </summary>  
 /// <seealso cref="EntityTypeBuilderBase{Country}" />  
 internal class LookupCountryMapping  
   : EntityTypeBuilderBase<LookupCountry>  
 {  
   /// <summary>  
   /// Initializes a new instance of the <see cref="LookupCountryMapping"/> class.  
   /// </summary>  
   public LookupCountryMapping()  
     : base("Country", "Lookup")  
   {  
   }  
   /// <summary>  
   /// Fluent mapping for the model.  
   /// </summary>  
   /// <param name="builder">The entity DB builder.</param>  
   public override void Map(EntityTypeBuilder<LookupCountry> builder)  
   {  
     builder.Property(model => model.Code).HasMaxLength(2);  
     builder.Property(model => model.IsDisabled);  
     builder.Property(model => model.Name).HasMaxLength(255);  
   }  
 }

In this, it is inherited from base class EntityTypeBuilderBase<LookupCountry> having constructor accepting table name and schema.
The overridden Map function is available to put fluent mapping. Since I have used my custom interface for Id mapping and it is being mapped on the base class, I have not put fluent mapping for same. Like I mentioned earlier this could be skipped, just that you have to put fluent mapping for primary key manually in that situation.

Application level FluentMapping class implementation

This class is the beholder of all fluent mappings for the entire application also it allows registering mappings in an easier manner. Let's first see the code then will have a look on explanation.

   /// <summary>  
   /// Fluent Mapping for the application.  
   /// </summary>  
   internal class FluentMapping  
   {  
     /// <summary>  
     /// The model builder  
     /// </summary>  
     private readonly ModelBuilder ModelBuilder;  
     /// <summary>  
     /// Initializes a new instance of the <see cref="FluentMapping"/> class.  
     /// </summary>  
     /// <param name="builder">The database model builder.</param>  
     internal FluentMapping(ModelBuilder builder)  
     {  
       ModelBuilder = builder;  
     }  
     /// <summary>  
     /// Fluent mapping for entire application.  
     /// </summary>  
     internal void Map()  
     {  
       BuildMap<LookupCountry, LookupCountryMapping>(ModelBuilder);  
     }  
     /// <summary>  
     /// Builds the DB model mapping.  
     /// </summary>  
     /// <typeparam name="TModel">The type of the model.</typeparam>  
     /// <typeparam name="TMapper">The type of the mapper.</typeparam>  
     /// <param name="dbModelBuilder">The database model builder.</param>  
     private static void BuildMap<TModel, TMapper>(ModelBuilder dbModelBuilder)  
       where TModel : class  
       where TMapper : EntityTypeBuilderBase<TModel>, new()  
     {  
       var map = new TMapper();  
       var builder = dbModelBuilder.Entity<TModel>();  
       map.Init(builder);  
       map.Map(builder);  
     }  
   }

The key highlights here are Map and BuildMap functions.

The BuildMap function is to create fluent mapping for entities with constraints like it has to be parameterless constructor class and inherited from EntityTypeBuilderBase class. This would allow to us to create a new object of mapper through Generic approach and call methods Init and Map from a base class in a convenient way for mapping.

The internal does not matter since we just need to add a mapping of an entity with related Mapper class in Map function.

 BuildMap<LookupCountry, LookupCountryMapping>(ModelBuilder);

It just says entity and Mapping class with ModelBuilder. Simple enough!

Registration of entire application fluent mapping on DbContext

This is a really straight forward implementation which does not need any explanation. Just need to create an object of FluentMapping class under OnModelCreating function.

 public sealed class MyProjectContext  
   : DbContext  
 {  
   public MyProjectContext(DbContextOptions option)  
     : base(option)  
   {  
   }  
   protected override void OnModelCreating(ModelBuilder builder)  
   {  
     var mapping = new FluentMapping.FluentMapping(builder);  
     mapping.Map();  
   }  
 }


Bonus material: Code Snippet for creating fluent mapping and registration code for same

If you have come so far, I have some bonus materials for composing FluentMapping class and registration of same (BuildMap code) through Visual Studio 20XX Snippet feature.

Please add these two files into Code Snippet Manager from VS 20XX.

FluentMapping.snippet

 <?xml version="1.0" encoding="utf-8"?>   
 <CodeSnippets xmlns="http://schemas.microsoft.com/VisualStudio/2005/CodeSnippet">   
  <CodeSnippet Format="1.0.0">   
   <Header>   
    <Title>Add A Fluent Mapping</Title>   
    <Author>Vikash Kumar</Author>   
    <Description>Fluent mapping structure.</Description>   
    <Shortcut>FluentMapping</Shortcut>   
   </Header>   
   <Snippet>   
    <Imports>   
     <Import>   
      <Namespace>MyProject.DB.FluentMapping.Base</Namespace>   
     </Import>   
           <Import>   
      <Namespace>Microsoft.EntityFrameworkCore.Metadata.Builders</Namespace>   
     </Import>   
    </Imports>   
    <Declarations>   
     <Literal>   
      <ID>modelname</ID>   
      <ToolTip>Replace with data model name</ToolTip>   
      <Default>MyModel</Default>   
     </Literal>  
    </Declarations>   
    <Code Language="CSharp">   
     <![CDATA[   
 /// <summary>  
 /// Fluent mapping for <see cref="$modelname$"/> entity.  
 /// </summary>  
 /// <seealso cref="EntityTypeBuilderBase{$modelname$}" />       
 internal class $modelname$Mapping  
      : EntityTypeBuilderBase<$modelname$>  
 {  
      /// <summary>  
      /// Initializes a new instance of the <see cref="$modelname$Mapping"/> class.  
      /// </summary>  
      public $modelname$Mapping()  
           : base(nameof($modelname$), Schema.Name)  
      {  
      }  
      /// <summary>  
      /// Fluent mapping for the model.  
      /// </summary>  
      /// <param name="builder">The entity DB builder.</param>  
      public override void Map(EntityTypeBuilder<$modelname$> builder)  
      {  
      }  
 }   
 ]]>   
    </Code>   
   </Snippet>   
  </CodeSnippet>   
 </CodeSnippets>


FluentRegistration.snippet

 <?xml version="1.0" encoding="utf-8" ?>  
 <CodeSnippets xmlns="http://schemas.microsoft.com/VisualStudio/2005/CodeSnippet">  
      <CodeSnippet Format="1.0.0">  
   <Header>   
    <Title>Fluent Mapping registration</Title>   
    <Author>Vikash Kumar</Author>   
    <Description>Fluent mapping registration.</Description>   
    <Shortcut>FluentMappingRegistration</Shortcut>   
   </Header>   
           <Snippet>  
                <Declarations>  
                     <Literal>  
                          <ID>model</ID>  
                          <ToolTip>Model to map</ToolTip>  
                          <Default>MyModel</Default>  
                     </Literal>  
                     <Literal>  
                          <ID>param</ID>  
                          <ToolTip>Model Builder Parameter.</ToolTip>  
                          <Default>ModelBuilder</Default>  
                     </Literal>  
                </Declarations>  
                <Code Language="csharp"><![CDATA[BuildMap<$model$, $model$Mapping>($param$);$end$]]>  
                </Code>  
           </Snippet>  
      </CodeSnippet>  
 </CodeSnippets>





Labels:

Comments

Post a Comment

Popular posts from this blog

Elegantly dealing with TimeZones in MVC Core / WebApi

In any new application handling TimeZone/DateTime is mostly least priority and generally, if someone is concerned then it would be handled by using DateTime.UtcNow on codes while creating current dates and converting incoming Date to UTC to save on servers. Basically, the process is followed by saving DateTime to UTC format in a database and keep converting data to native format based on user region or single region in the application's presentation layer. The above is tedious work and have to be followed religiously. If any developer misses out the manual conversion, then that area of code/view would not work. With newer frameworks, there are flexible ways to deal/intercept incoming or outgoing calls to simplify conversion of TimeZones. These are steps/process to achieve it. 1. Central code for storing user's state about TimeZone. Also, central code for conversion logic based on TimeZones. 2. Dependency injection for the above class to ...
4 comments
Read more

Making FluentValidation compatible with Swagger including Enum or fixed List support

FluentValidation is not directly compatible with Swagger API to validate models. But they do provide an interface through which we can compose Swagger validation manually. That means we look under FluentValidation validators and compose Swagger validator properties to make it compatible. More of all mapping by reading information from FluentValidation and setting it to Swagger Model Schema. These can be done on any custom validation from FluentValidation too just that proper schema property has to be available from Swagger. Custom validation from Enum/List values on FluentValidation using FluentValidation.Validators; using System.Collections.Generic; using System.Linq; using static System.String; /// <summary> /// Validator as per list of items. /// </summary> /// <seealso cref="PropertyValidator" /> public class FixedListValidator : PropertyValidator { /// <summary> /// Gets the valid items /// <...
1 comment
Read more

Handling JSON DateTime format on Asp.Net Core

This is a very simple trick to handle JSON date format on AspNet Core by global settings. This can be applicable for the older version as well. In a newer version by default, .Net depends upon Newtonsoft to process any JSON data. Newtonsoft depends upon Newtonsoft.Json.Converters.IsoDateTimeConverter class for processing date which in turns adds timezone for JSON data format. There is a global setting available for same that can be adjusted according to requirement. So, for example, we want to set default formatting to US format, we just need this code. services.AddMvc() .AddJsonOptions(options => { options.SerializerSettings.DateTimeZoneHandling = "MM/dd/yyyy HH:mm:ss"; });
1 comment
Read more

Architecture solution composting Repository Pattern, Unit Of Work, Dependency Injection, Factory Pattern and others

Project architecture is like garden, we plant the things in certain order and eventually they grow in similar manner. If things are planted well then they will all look(work) great and easier to manage. If they grow as cumbersome it would difficult to maintain and with time more problems would be happening in maintenance. There is no any fixed or known approach to decide project architecture and specially with Agile Methodology. In Agile Methodology, we cannot predict how our end products will look like similarly we cannot say a certain architecture will fit well for entire development lifespan for project. So, the best thing is to modify the architecture as per our application growth. I understand that it sounds good but will be far more problematic with actual development. If it is left as it is then more problems will arise with time. Just think about moving plant vs a full grown tree. Coming to technical side, In this article, I will be explaining about the various techniques ...
Post a Comment
Read more

Using Redis distributed cache in dotnet core with helper extension methods

Redis cache is out process cache provider for a distributed environment. It is popular in Azure Cloud solution, but it also has a standalone application to operate upon in case of small enterprises application. How to install Redis Cache on a local machine? Redis can be used as a local cache server too on our local machines. At first install, Chocolatey https://chocolatey.org/ , to make installation of Redis easy. Also, the version under Chocolatey supports more commands and compatible with Official Cache package from Microsoft. After Chocolatey installation hit choco install redis-64 . Once the installation is done, we can start the server by running redis-server . Distributed Cache package and registration dotnet core provides IDistributedCache interface which can be overrided with our own implementation. That is one of the beauties of dotnet core, having DI implementation at heart of framework. There is already nuget package available to override IDistributedCache i...
3 comments
Read more

Kendo MVC Grid DataSourceRequest with AutoMapper

Kendo Grid does not work directly with AutoMapper but could be managed by simple trick using mapping through ToDataSourceResult. The solution works fine until different filters are applied. The problems occurs because passed filters refer to view model properties where as database model properties are required after AutoMapper is implemented. So, the plan is to intercept DataSourceRequest  and modify names based on database model. To do that we are going to create implementation of  CustomModelBinderAttribute to catch calls and have our own implementation of DataSourceRequestAttribute from Kendo MVC. I will be using same source code from Kendo but will replace column names for different criteria for sort, filters, group etc. Let's first look into how that will be implemented. public ActionResult GetRoles([MyDataSourceRequest(GridId.RolesUserGrid)] DataSourceRequest request) { if (request == null) { throw new Argume...
Post a Comment
Read more

Configuring Ninject, Asp.Net Identity UserManager, DataProtectorTokenProvider with Owin

It can be bit tricky to configure both Ninject and Asp.Net Identity UserManager if some value is expected from DI to configure UserManager. We will look into configuring both and also use OwinContext to get UserManager. As usual, all configuration need to be done on Startup.cs. It is just a convention but can be used with different name, the important thing is to decorate class with following attribute to make it Owin start-up: [assembly: OwinStartup(typeof(MyProject.Web.Startup))] Ninject configuration Configuring Ninject kernel through method which would be used to register under Owin. Startup.cs public IKernel CreateKernel() { var kernel = new StandardKernel(); try { //kernel.Bind<IHttpModule>().To<HttpApplicationInitializationHttpModule>(); // TODO: Put any other injection which are required. return kernel; } catch { kernel.Dispose(); thro...
Post a Comment
Read more

Using LINQ to Entity efficiently with First/FirstOrDefault/Last/LastOrDefault/Single/SingleOrDefault

We generally use these extension methods First/FirstOrDefault/Last/LastOrDefault/Single/SingleOrDefault with predicates like ctx=> ctx.Model.FirstOrDefault(item => item.Id == 1 ) Or ctx=> ctx.Model.Where(item => item.Id == 1 ).FirstOrDefault() What is the problem with these? FirstOrDefault or similar methods immediately loads all data at once. So, let's say we have fifty columns on table then all those columns data would be retrieved from DB and saved into memory. This link gives a fair idea of different function behavior.  https://msdn.microsoft.com/en-us/library/bb882641.aspx .  So, even if we require only one value from selected field it retrieves all values. What is the solution? The solution is pretty simple. Whenever we need selected items better to do projection before calling FirstOrDefault or similar methods. Ex: Selecting single item ctx.Model.Where(itm => itm.Id == 1) .Select(itm => itm.Name).FirstO...
Post a Comment
Read more

Data seed for the application with EF, MongoDB or any other ORM.

Most of ORMs has moved to Code first approach where everything is derived/initialized from codes rather than DB side. In this situation, it is better to set data through codes only. We would be looking through simple technique where we would be Seeding data through Codes. I would be using UnitOfWork and Repository pattern for implementing Data Seeding technique. This can be applied to any data source MongoDB, EF, or any other ORM or DB. Things we would be doing. - Creating a base class for easy usage. - Interface for Seed function for any future enhancements. - Individual seed classes. - Configuration to call all seeds. - AspNet core configuration to Seed data through Seed configuration. Creating a base class for easy usage public abstract class BaseSeed<TModel> where TModel : class { protected readonly IMyProjectUnitOfWork MyProjectUnitOfWork; public BaseSeed(IMyProjectUnitOfWork MyProjectUnitOfWork) { ...
Post a Comment
Read more

Visual Studio 2015 Code Analyzer and configuration with StyleCop

What is Diagnostic/Code Analyzer? To put it simply it is something similar to Resharper or Telerik JustCode. It analyzes codes while writing on code editor and suggest for improvements of codes through Squiggles, light icon and based on various severity. How it works? I had mentioned that it is similar to Resharper and Telerik JustCode but internal infrastructure is completely different. It is dependent on new compiler Roslyn . Roslyn has a clever compile technique, unlike older version which makes it faster and flexible for dynamic compilation without the need of the entire code base. The structure is basically divided into two categories Syntax Tree , and Semantic Model . The syntax tree is related to syntaxes only it does not require any reference check. It can be related to DOM elements structure in case of HTML.  Syntax Tree consists of very fine details as simple as WhiteSpace under the code. The Semantic Model is kind of references of Syntax Tree in which it ...
Post a Comment
Read more