Skip to main content

Dependency Injection through XML configuration and XML transformation through SlowCheetah

Dependency Injection (DI) is a design pattern to change definition by substituting object without changing code for the application. The most popular DI type is to construct classes based on certain interface and pass actual object on constructor level.

What are we trying to do?
We will be looking into a way to achieve dependency injection through XML configuration based on build selection. The implemented classes derived through interface will get switched based on build selection.

Where to use it?
I really hate making dependencies with something specific which can be changed later on. In my case, Azure environment. I believe Azure is more like a platform where we can host the application rather then integrating the application with Azure. What if client decided to switch to other hosting environment, in that case we got to change every piece of code wherever Azure SDKs are referred.

The above one is merely an example. We can use this approach on many other item as well.

What tools are used?
Ninject(http://www.nuget.org/packages/Ninject): This is going to used for dependency injection.
Ninjeect.Extensions.Xml (http://www.nuget.org/packages/Ninject.Extensions.Xml): This will be used to construct Ninject kernel through XML file.
SlowCheetah (http://visualstudiogallery.msdn.microsoft.com/69023d00-a4f9-4a34-a6cd-7e854ba318b5): An extension of Visual Studio to transform config or XML files.

Processes to do DI through SlowCheetah
I am expecting that you have installed the above tools at this point.

Step 1 - Creating main XML:
Let's start by creating NinjectInjection.xml file with required injections.

 <?xml version="1.0" encoding="utf-8" ?>  
 <module name="MyProjectInjection">  
  <bind  
   service="MyProject.Interface.Cache.ICacheWrapper, MyProject.Interface"  
   to="MyProject.Core.Caching.AppMemoryCache, MyProject.Core" />  
  <bind  
   service="MyProject.Interface.Cache.IAppCache, MyProject.Interface"  
   to="MyProject.Core.Caching.AppCache, MyProject.Core" />  
  <bind  
   service="MyProject.Interface.Uploader.IFileUpload, MyProject.Interface"  
   to="MyProject.Core.Uploader.Local.LocalFileUpload, MyProject.Core" />  
 </module>  

You can see, I have configured injections for Caching and File uploading mechanism which will support local file system and Memory Caching on IIS. Based on selection of build we will switch definition to Azure Caching and Azure BLOB storage or normal IIS approach.

Step 2 - Creating dependent XML files:
Right click on created  XML file and select Add Transform which will generate up XML files based on build profiles.





Generated XML files. In this case, I am having NinjectInjection.AzureLocalTest.xml as extra item as per my build configuration profile.





Step 3 - Transforming XML files based on our need:
The idea is to find particular element (bind element) in desired XML file and change the value of it. XSLT or Microsoft XML Document Transform (http://msdn.microsoft.com/en-us/library/dd465326(VS.100).aspx) can be used.
Let's change the values on NinjectInjection.Release.xml file.

 <?xml version="1.0" encoding="utf-8" ?>  
 <!-- For more information on using transformations   
    see the web.config examples at http://go.microsoft.com/fwlink/?LinkId=214134. -->  
 <module xmlns:xdt="http://schemas.microsoft.com/XML-Document-Transform">  
  <bind  
   service="MyProject.Interface.Cache.ICacheWrapper, MyProject.Interface"  
   to="MyProject.Core.Caching.AzureCacheWrapper, MyProject.Core"  
   xdt:Transform="SetAttributes" xdt:Locator="Match(service)"/>  
  <bind  
   service="MyProject.Interface.Cache.IAppCache, MyProject.Interface"  
   to="MyProject.Core.Caching.AzureAppCache, MyProject.Core"  
   xdt:Transform="SetAttributes" xdt:Locator="Match(service)"/>  
  <bind  
   service="MyProject.Interface.Uploader.IFileUpload, MyProject.Interface"  
   to="MyProject.Core.Uploader.Azure.AzureFileUpload, MyProject.Core"  
   xdt:Transform="SetAttributes" xdt:Locator="Match(service)"/>  
 </module>  

xdt:Locator="Match(service)" is to find element with specified attribute value and xdt:Transform="SetAttributes" to set new value.

We can check transformation text by right clicking NinjectInjection.Release.xml file and selecting Preview Transform which will result as:
XML Transformation Preview


Step 3 - Setting up Ninject kernel to load injections through XML file:

Let's first configure XML file to move into project's bin directory on successful build of application. Right click NinjectInjection.xml file and select Properties to set Copy to Output Directory as Copy to always or Copy to newer.














This will always get transformed XML file based on build configuration profile.

Now, just registration need to be done on Ninject kernel. Ideally, NinjectWebCommon file gets created under App_Start folder. On RegisterServices function put these to configure kernel.

       kernel.Load(Assembly.GetExecutingAssembly());  
       var ninjectConfig = Path.Combine(AppDomain.CurrentDomain.SetupInformation.ApplicationBase, "bin//NinjectInjection.xml");  
       if (File.Exists(ninjectConfig))  
       {  
         kernel.Load(ninjectConfig);  
       }  

The above code will look into bin directory by name of NinjectInjection.xml and configure kernel. Based on build configuration profile selection, contents of this file will keep changing.

Comments

Popular posts from this blog

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 /// <...

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 ...

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...

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...

LDAP with ASP.Net Identity Core in MVC with project.json

Lightweight Directory Access Protocol (LDAP), the name itself explain it. An application protocol used over an IP network to access the distributed directory information service. The first and foremost thing is to add references for consuming LDAP. This has to be done by adding reference from Global Assembly Cache (GAC) into project.json "frameworks": { "net461": { "frameworkAssemblies": { "System.DirectoryServices": "4.0.0.0", "System.DirectoryServices.AccountManagement": "4.0.0.0" } } }, These  System.DirectoryServices  and  System.DirectoryServices.AccountManagement  references are used to consume LDAP functionality. It is always better to have an abstraction for irrelevant items in consuming part. For an example, the application does not need to know about PrincipalContext or any other dependent items from those two references to make it extensible. So, we can begin wi...

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"; });

Trim text in MVC Core through Model Binder

Trimming text can be done on client side codes, but I believe it is most suitable on MVC Model Binder since it would be at one place on infrastructure level which would be free from any manual intervention of developer. This would allow every post request to be processed and converted to a trimmed string. Let us start by creating Model binder using Microsoft.AspNetCore.Mvc.ModelBinding; using System; using System.Threading.Tasks; public class TrimmingModelBinder : IModelBinder { private readonly IModelBinder FallbackBinder; public TrimmingModelBinder(IModelBinder fallbackBinder) { FallbackBinder = fallbackBinder ?? throw new ArgumentNullException(nameof(fallbackBinder)); } public Task BindModelAsync(ModelBindingContext bindingContext) { if (bindingContext == null) { throw new ArgumentNullException(nameof(bindingContext)); } var valueProviderResult = bindingContext.ValueProvider.GetValue(bin...

Custom SPA engine, similar to MVC pattern by using TypeScript

Single Page Application, a fundamental requirement for SPA is to develop the application with XMLHttpRequest (XHR) or AJAX. That is only main requirement, other things come as add-on stuff. Advancements of SPA? In today's world, we do not want to be restricted with basic features or functionalities. We want everything like any new Phone comes in market with some new shiny feature. There are a lot of functionalities available with SPA libraries and could be extended with more extension to have richer and easier implementation. To be specific we shall refer it as frameworks, not libraries. Earlier days one-way, two-way data binding with templates were very minimum things to expect from frameworks. Now they talk about component structure, Virtual Dom, IOC, state management, performance etc. Why building own framework/library? What I believe and experienced is each SPA JS Frameworks has its own set of rules and structure that has to be followed. If we want to have our own dyn...

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 ...

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...