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Unit Of Work injection through Asp.Net Core Dependency Injection

This article is not directly related to UnitOfWork but leveraging Asp.Net Core Dependency Injection to consume Unit Of Work.

In one of the previous article about project architecture, I was not very satisfied with the approach for Unit Of Work implementation for initialization of repository even if with some advantage.

Here is old code for UnitOfWork.

  public sealed partial class MyProjectUnitOfWork   
    : UnitOfWork<DbContext>, IMyProjectUnitOfWork   
   {   
    public MyProjectUnitOfWork(IContextFactory<DbContext> contextFactory)   
     : base(contextFactory)   
    {   
    }   
    /// <summary>   
    /// BookRepository holder   
    /// </summary>   
    private MyProject.DB.Repository.BookRepository _bookRepository;   
    /// <summary>   
    /// Gets the BookRepository repository.   
    /// </summary>   
    /// <value>   
    /// The BookRepository repository.   
    /// </value>   
    MyProject.Interface.Repository.IBookRepository IMyProjectUnitOfWork.BookRepository   
    {   
     get   
     {   
      return _bookRepository =   
      _bookRepository ?? new MyProject.DB.Repository.BookRepository(Context);   
     }   
    }   
   }   

The major reason for dissatisfaction was due to direct initialization of those repositories. Even if it lazy initialization and globally at one place but still the direct dependency.

So, what changed in the Asp.Net Core DI that in the earlier code I have not accommodated. Actually it does not change, in fact, the DIs libraries are more feature rich in comparison of Asp.Net Core DI. The only good thing is we would not generally depend on any third party libraries since there is built in the library available with Framework itself. So, this gives freedom to use DI related codes on dependent projects without much worrying about that DI framework could change in future.

After keeping this in mind what all need to be changed:

  1. MyProjectUnitOfWork implementation to get repository in a new way.
  2. Constructor change to resolve service through Service Provider.
  3. Initialization of DIs for repositories.
  4. Making entry point in Startup.cs 

MyProjectUnitOfWork T4 for code generation


 <#@ template debug="true" hostSpecific="true" #>  
 <#@ output extension=".cs" #>  
 <#@ Assembly Name="System.Core" #>  
 <#@ import namespace="System" #>  
 <#@ import namespace="EnvDTE" #>  
 <#@ import namespace="EnvDTE80" #>  
 <#@ import namespace="System" #>  
 <#@ import namespace="System.IO" #>  
 <#@ import namespace="System.Diagnostics" #>  
 <#@ import namespace="System.Linq" #>  
 <#@ import namespace="System.Collections" #>  
 <#@ import namespace="System.Collections.Generic" #>   
 <#@ include file="EF.Utility.CS.ttinclude"#>  
 <#@ include file="../../T4Plugin/VisualStudioAutomationHelper.ttinclude" #>  
 <#@ include file="../../T4Plugin/MultiOutput.ttinclude" #>  
 <#  
   var modelProjectNamespace = "MyProject.Model";  
   var modelNamespace = "MyProject.Model.DataModel";  
   var modelNamespaceReplace = "MyProject.Interface.Repository";  
   var repositoryNamespace = "MyProject.DB.Repository";  
   CodeGenerationTools code = new CodeGenerationTools(this);  
   var codeDom = CodeDomProvider.CreateProvider("C#");  
   var modelProject = VisualStudioHelper.GetProject(modelProjectNamespace);  
   var allModelClasses = VisualStudioHelper.GetAllCodeElementsOfType(modelProject.CodeModel.CodeElements, EnvDTE.vsCMElement.vsCMElementClass, false);  
   var types = (from modelClass in allModelClasses.OfType<CodeClass2>()  
       where modelClass.FullName.StartsWith(modelNamespace) &&   
         !modelClass.FullName.EndsWith("MetadataSource")  
       select modelClass  
     ).OrderBy(clas=>clas.FullName);  
 #>  
 //------------------------------------------------------------------------------  
 // <auto-generated>  
 //   This code was generated from a template and will be re-created if deleted  
 //       with default implementation.  
 // </auto-generated>  
 //------------------------------------------------------------------------------  
 using System;  
 using MyProject.Interface.Infrastructure;  
 using Microsoft.EntityFrameworkCore;  
 using Microsoft.Extensions.DependencyInjection;  
 namespace <#=    code.VsNamespaceSuggestion()#>  
 {  
   /// <summary>  
   /// MyProject implementation of Unit of Work  
   /// </summary>  
      public sealed partial class MyProjectUnitOfWork  
           : IMyProjectUnitOfWork  
      {  
     /// <summary>  
     /// The service provider  
     /// </summary>  
     private readonly IServiceProvider ServiceProvider;  
     /// <summary>  
     /// Initializes a new instance of the <see cref="MyProjectUnitOfWork"/> class.  
     /// </summary>  
     /// <param name="dbContext">The database context.</param>  
     /// <param name="serviceProvider">The service provider.</param>  
     public MyProjectUnitOfWork(MyProjectContext dbContext, IServiceProvider serviceProvider)  
       : base(dbContext)  
     {  
       ServiceProvider = serviceProvider;  
     }  
                          <#  
   foreach (var type in types)  
   {  
     var nameSpace = type.Namespace.Name.Replace(modelNamespace,repositoryNamespace);  
     var interfaceNameSpace = type.Namespace.Name.Replace(modelNamespace,modelNamespaceReplace);  
     var name = type.Name + "Repository";  
     var fullName = nameSpace + "." + name;  
           var interfaceFullName = $"{interfaceNameSpace}.I{type.Name}Repository";  
                #>  
           /// <summary>  
           /// <#=      name #> holder  
           /// </summary>  
     private <#=      fullName #> _<#=      code.CamelCase(name) #>;  
     /// <summary>  
     /// Gets the <#=      type.Name #>Repository repository.  
     /// </summary>  
     /// <value>  
     /// The <#=      type.Name #>Repository repository.  
     /// </value>  
     <#=interfaceFullName#> IMyProjectUnitOfWork.<#=      type.Name #>Repository   
     {   
          get  
          {  
                     return ServiceProvider.GetService<<#=      fullName #>>();  
          }  
     }  
      <#}  
      #>}  
 }  

The above would generate

 //------------------------------------------------------------------------------  
 // <auto-generated>  
 //   This code was generated from a template and will be re-created if deleted  
 //       with default implementation.  
 // </auto-generated>  
 //------------------------------------------------------------------------------  
 using System;  
 using MyProject.Interface.Infrastructure;  
 using Microsoft.EntityFrameworkCore;  
 using Microsoft.Extensions.DependencyInjection;  
 namespace MyProject.DB.Infrastructure  
 {  
   /// <summary>  
   /// MyProject implementation of Unit of Work  
   /// </summary>  
      public sealed partial class MyProjectUnitOfWork  
           : IMyProjectUnitOfWork  
      {  
     /// <summary>  
     /// The service provider  
     /// </summary>  
     private readonly IServiceProvider ServiceProvider;  
     /// <summary>  
     /// Initializes a new instance of the <see cref="MyProjectUnitOfWork"/> class.  
     /// </summary>  
     /// <param name="dbContext">The database context.</param>  
     /// <param name="serviceProvider">The service provider.</param>  
     public MyProjectUnitOfWork(MyProjectContext dbContext, IServiceProvider serviceProvider)  
       : base(dbContext)  
     {  
       ServiceProvider = serviceProvider;  
     }  
           /// <summary>  
           /// BookRepository holder  
           /// </summary>  
     private MyProject.DB.Repository.BookRepository _bookRepository;  
     /// <summary>  
     /// Gets the BookRepository repository.  
     /// </summary>  
     /// <value>  
     /// The BookRepository repository.  
     /// </value>  
     MyProject.Interface.Repository.IBookRepository IMyProjectUnitOfWork.BookRepository   
     {   
          get  
          {  
                     return ServiceProvider.GetService<MyProject.DB.Repository.BookRepository>();  
          }  
     }  
      }  
 }  

By looking into the code, it is just using ServiceProvider to get the registered services.

Now, need to write code to register service. This again would be populated through T4 and dependency injection codes.

T4 to generate DI codes for Repositories 

 <#@ template debug="true" hostSpecific="true" #>  
 <#@ output extension=".cs" #>  
 <#@ Assembly Name="System.Core" #>  
 <#@ import namespace="System" #>  
 <#@ import namespace="EnvDTE" #>  
 <#@ import namespace="EnvDTE80" #>  
 <#@ import namespace="System" #>  
 <#@ import namespace="System.IO" #>  
 <#@ import namespace="System.Diagnostics" #>  
 <#@ import namespace="System.Linq" #>  
 <#@ import namespace="System.Collections" #>  
 <#@ import namespace="System.Collections.Generic" #>   
 <#@ include file="EF.Utility.CS.ttinclude"#>  
 <#@ include file="../../../T4Plugin/VisualStudioAutomationHelper.ttinclude" #>  
 <#@ include file="../../../T4Plugin/MultiOutput.ttinclude" #>  
 <#  
   var modelProjectNamespace = "MyProject.Model";  
   var modelNamespace = "MyProject.Model.DataModel";  
   var modelNamespaceReplace = "MyProject.Interface.Repository";  
   var repositoryNamespace = "MyProject.DB.Repository";  
   CodeGenerationTools code = new CodeGenerationTools(this);  
   var codeDom = CodeDomProvider.CreateProvider("C#");  
   var modelProject = VisualStudioHelper.GetProject(modelProjectNamespace);  
   var allModelClasses = VisualStudioHelper.GetAllCodeElementsOfType(modelProject.CodeModel.CodeElements, EnvDTE.vsCMElement.vsCMElementClass, false);  
   var types = (from modelClass in allModelClasses.OfType<CodeClass2>()  
       where modelClass.FullName.StartsWith(modelNamespace) &&   
         !modelClass.FullName.EndsWith("MetadataSource")  
       select modelClass  
     ).OrderBy(clas=>clas.FullName);  
 #>  
 //------------------------------------------------------------------------------  
 // <auto-generated>  
 //   This code was generated from a template and will be re-created if deleted  
 //       with default implementation.  
 // </auto-generated>  
 //------------------------------------------------------------------------------  
 using Microsoft.Extensions.DependencyInjection;  
 namespace <#=    code.VsNamespaceSuggestion()#>  
 {  
   /// <summary>  
   /// Registration of repository with Dependency Injection.  
   /// </summary>  
      public static class ExtensionUnitOfWorkService  
      {  
     /// <summary>  
     /// Registers the repositories.  
     /// </summary>  
     /// <param name="service">The service collection.</param>  
           public static void RegisterRepositories(this IServiceCollection service)  
           {  
 <#  
   foreach (var type in types)  
   {  
     var nameSpace = type.Namespace.Name.Replace(modelNamespace,repositoryNamespace);  
     var interfaceNameSpace = type.Namespace.Name.Replace(modelNamespace,modelNamespaceReplace);  
     var name = type.Name + "Repository";  
     var fullName = nameSpace + "." + name;  
           var interfaceFullName = $"{interfaceNameSpace}.I{type.Name}Repository";  
           #>               service.AddScoped<<#= interfaceFullName #>, <#= fullName #>>();  
 <#  
   }#>          }  
      }  
 }  

Once executed it would generate codes to map Repository interfaces with respective classes.

 //------------------------------------------------------------------------------  
 // <auto-generated>  
 //   This code was generated from a template and will be re-created if deleted  
 //       with default implementation.  
 // </auto-generated>  
 //------------------------------------------------------------------------------  
 using Microsoft.Extensions.DependencyInjection;  
 namespace MyProject.DB.Infrastructure.Configuration  
 {  
   /// <summary>  
   /// Registration of repository with Dependency Injection.  
   /// </summary>  
      public static class ExtensionUnitOfWorkService  
      {  
     /// <summary>  
     /// Registers the repositories.  
     /// </summary>  
     /// <param name="service">The service collection.</param>  
           public static void RegisterRepositories(this IServiceCollection service)  
           {  
                service.AddScoped<MyProject.Interface.Repository.IBookRepository, MyProject.DB.Repository.BookRepository>();  
           }  
      }  
 }  



Two things are done by now MyProjectUnitOfWork properties implementation to get Repositories from ServiceProvider and then mappings of Repository interface to respective classes on ExtensionUnitOfWorkService class.

DbContext registration and above services registration

 /// <summary>  
 /// DB Configuration.  
 /// </summary>  
 public static class ExtensionRepositoryConfiguration  
 {  
   /// <summary>  
   /// Adds the database configuration to MVC Core.  
   /// </summary>  
   /// <param name="services">The services.</param>  
   /// <param name="configuration">The configuration.</param>  
   /// <param name="connectionName">Name of the connection.</param>  
   public static void AddDb(this IServiceCollection services,  
     IConfigurationRoot configuration, string connectionName)  
   {  
     services.AddDbContext<MyProjectContext>(options =>  
     {  
       options.UseSqlServer(connectionName,  
         serverOption => serverOption.MigrationsAssembly("MyProject.Web"));  
     });  
     services.AddScoped<IMyProjectUnitOfWork>((serv) =>  
     {  
       return new MyProjectUnitOfWork(serv.GetService<MyProjectContext>(), serv);  
     });  
     services.RegisterRepositories();  
   }  
 }  


All DIs for Repositories are done by calling RegisterRepositories and general Context injection.

Finally, on Startup.cs, need to call this.

 services.AddDb(Configuration, Configuration.GetConnectionString("SqlDatabaseDevelopment"));  


SOURCE CODE: https://github.com/viku85/RepositoryUnitOfWorkDiSample

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