Skip to main content

T4, Generating interface automatically based on provided classes

With new techniques and patterns interface plays a key role in application architecture. Interface makes application extendable like defining file upload interface and implementing based on file system, Azure Blob storage, Amazon S3. At starting we might be implementing based on Azure Blob but later we might move to Windows based file system and so on.

Ideally we create interface based on need and start implementing actual default implementation class. Many a times at starting of implementation there is one to one mapping between Interface and Class. Like from above example File upload interface and the initial or default class implementation that we design and with time it will get extended.

In this article, we will try to create interface based on default class implementation. This is not at all recommended in Test Driven Design (TDD) where we test the application before actual code implementation but I feel sometimes and in some situations it is okay do that and test straight after creation. Like couple of  months back, I had written an article on Dependency Injection, Repository Pattern and other related patterns (http://vikutech.blogspot.com/2015/01/architecture-solution-composting-repository-pattern-unit-of-work-dependency-injection-factory-pattern.html) where we had created repository interface and then created actual classes. If we have lot of database models or frequent additions in functions then we need to do copy paste of function implementation on classes based on addition in interface.

In this way we can develop application little faster where application demands frequent additions of function. This example is based on upon the repository classes from above link. The idea is to generate interfaces automatically based on repository classes modification. This technique can be found with various tools like Re-sharper, Telerik JustCode etc to refactor codes by extracting interface from class but over here it is through T4.

Resources used 
I have took help of two libraries to read project files and to create multiple files.
MultiOutput.ttinclude (https://github.com/subsonic/SubSonic-3.0-Templates/blob/master/ActiveRecord/MultiOutput.ttinclude) : This is to generate multiple files through single T4 file.
VisualStudioAutomationHelper.ttinclude (https://github.com/PombeirP/T4Factories/blob/master/T4Factories.Testbed/CodeTemplates/VisualStudioAutomationHelper.ttinclude) : This will help us in reading files from different project.
NOTE: Please change path of these files based on path in your project.
 <#@ template debug="true" hostSpecific="true" #>  
 <#@ output extension=".cs" #>  
 <#@ Assembly name="EnvDTE" #>  
 <#@ Assembly name="EnvDTE80" #>  
 <#@ Assembly name="System.ComponentModel.DataAnnotations" #>  
 <#@ import namespace="EnvDTE" #>  
 <#@ import namespace="EnvDTE80" #>  
 <#@ import namespace="System" #>  
 <#@ import namespace="System.Linq" #>  
 <#@ import namespace="System.Xml" #>  
 <#@ import namespace="System.Collections" #>  
 <#@ import namespace="System.Collections.Generic" #>  
 <#@ import namespace="System.ComponentModel.DataAnnotations" #>  
 <#@ import namespace="System.Text.RegularExpressions" #>  
 <#@ include file="T4Plugin/VisualStudioAutomationHelper.ttinclude" #>  
 <#@ include file="T4Plugin/MultiOutput.tt" #>  
 <#  
   var dbProjectNamespace = "MyProject.DB";  
   var modelProjectNamespace = "MyProject.Model";  
   var repositoryNamespace = dbProjectNamespace + ".Repository";  
   var domainModelNamespace = modelProjectNamespace + ".DomainModel";  
   var repositoryInterfaceNamespace = "MyProject.Interface.Repository";  
   // Get a reference to the current project.  
   var dbProject = VisualStudioHelper.GetProject(dbProjectNamespace);  
   // Database model project  
   var modelProject = VisualStudioHelper.GetProject(modelProjectNamespace);  
   // Get all class items from the code model  
   var allRepoClasses = VisualStudioHelper.  
     GetAllCodeElementsOfType(dbProject.CodeModel.CodeElements, EnvDTE.vsCMElement.vsCMElementClass, false)  
     .Where(model => model.FullName.StartsWith(repositoryNamespace));  
   var allModelClasses = VisualStudioHelper.GetAllCodeElementsOfType(modelProject.CodeModel.CodeElements,   
             EnvDTE.vsCMElement.vsCMElementClass, false);  
   // Iterate all database models   
   foreach(CodeClass2 modelClass in allModelClasses  
     .OfType<CodeClass>().Where(clas => clas.FullName.StartsWith(domainModelNamespace) &&   
     !clas.FullName.EndsWith("MetadataSource")  
     ).OrderBy(clas => clas.FullName))  
   {  
     var fileName = "I" + modelClass.Name + "Repository.Generated.cs";  
     // Replace model namespace with repository namespace  
     var nameSpace = modelClass.Namespace.Name.Replace(domainModelNamespace, repositoryInterfaceNamespace);  
     #>  
 namespace <#= nameSpace #>  
 {  
   //------------------------------------------------------------------------------  
   // <auto-generated>  
   //   This code was generated from a template and will be re-created if deleted  
   //       with default values if executed.  
   // </auto-generated>  
   //------------------------------------------------------------------------------  
   using <#= modelClass.Namespace.Name #>;  
   using System;  
   /// <summary>  
   /// Interface to interact with <see cref="<#= modelClass.FullName#>"/> domain model.  
   /// </summary>  
   public partial interface I<#= modelClass.Name#>Repository  
        : IRepository<<#= modelClass.Name#>>  
   {  
 <#  
     // Repository classes  
     foreach(var repoClass in allRepoClasses.OfType<CodeClass2>().  
       Where(model => model.Name == modelClass.Name + "Repository"))  
     {  
       foreach(var partialClas in repoClass.PartialClasses.OfType<CodeClass2>())  
       {  
         var allFunctions = VisualStudioHelper.GetAllCodeElementsOfType(partialClas.Members, EnvDTE.vsCMElement.vsCMElementFunction, false);  
         foreach(var func in allFunctions.OfType<CodeFunction2>()  
           .Where(fun => fun.Name != modelClass.Name + "Repository"))  
         {  
           string strDoc=String.Empty;  
           if(!string.IsNullOrEmpty(func.DocComment) &&   
             func.Name != modelClass.Name + "Repository"){  
             var lines = func.DocComment.Split('\n');  
             for(int idx = 1; idx < (lines.Length-1); idx++) {  
                 #>   /// <#= lines[idx] #> <#  
             }  
           }  
                      #>  
     <#= GenerateFunctionStub(func) #>  
  <#  
         }  
       }  
     }      
     #>  
   }  
 }  
 <#  
     SaveOutput(fileName);  
     DeleteOldOutputs();  
   }  
 #>  
 <#+  
   private string GenerateFunctionStub(CodeFunction2 func)  
   {  
     var parametrs = new StringBuilder();  
     foreach (var item in func.Parameters.OfType<CodeParameter2>()) {  
       if ((parametrs.Length > 0)) {  
         parametrs.Append(", ");  
       }  
       // TODO: Implement other parameter kind  
       switch (item.ParameterKind)  
       {  
         case vsCMParameterKind.vsCMParameterKindOut:  
           parametrs.Append("out ");  
           break;  
         case vsCMParameterKind.vsCMParameterKindRef:  
           parametrs.Append("ref ");  
           break;  
         default:  
           break;  
       }  
       parametrs.AppendFormat("{0} {1}",  
           (item.Type.AsFullName.StartsWith("System") ?  
           "global::" + (item.Type.AsFullName.StartsWith("System.Nullable<System")?  
                   item.Type.AsFullName.Replace("System.Nullable<System", "System.Nullable<global::System") :  
                   item.Type.AsFullName  
                   )  
           : item.Type.AsFullName)  
           , item.FullName);  
     }  
     // Build up the line from the function  
     var funcBody = new StringBuilder();  
     funcBody.AppendFormat("{0}{1} {2}({3})",   
       (func.Type.AsFullName.StartsWith("System") ? "global::" +  
       func.Type.AsFullName.Replace("<System","<global::System").Replace(",System", ",global::System")  
       :func.Type.AsFullName)  
       ,string.IsNullOrEmpty(func.Type.AsFullName) ? "void" : ""  
       , func.Name, parametrs);  
     if (func.FunctionKind == EnvDTE.vsCMFunction.vsCMFunctionConstant) {  
       funcBody.Append(" const");  
     }  
     funcBody.Append(";");  
     return funcBody.ToString();  
   }  
   public string GetXmlComment(string xmlDocComment, int tabAddition)  
   {  
     if(!string.IsNullOrEmpty(xmlDocComment)){  
       return string.Empty;  
     }  
     var comment = new StringBuilder();  
     string appender = string.Empty;  
     for(int tabCtr = 0; tabCtr < tabAddition; tabCtr++){  
       appender += "\t";  
     }  
     var lines = xmlDocComment.Split('\n');  
     for(int ctrLine = 1; ctrLine < (lines.Length-1); ctrLine++){  
       comment.AppendFormat("{0} {1}", appender, lines[ctrLine]);  
     }  
     return comment.ToString();  
   }  
  #>  

var dbProjectNamespace = "MyProject.DB": Database layer project name.
var modelProjectNamespace = "MyProject.Model": Database model project name.
var repositoryNamespace = dbProjectNamespace + ".Repository": Repository namespace from where actual class files would be read to generate interface.
var domainModelNamespace = modelProjectNamespace + ".DomainModel": The database model classes for generating interfaces. Based on these files interfaces are generated for model.
   var repositoryInterfaceNamespace = "MyProject.Interface.Repository": The actual interface repository namespace.

This T4 can generate interfaces, function with written XML comments via repository classes.

Similarly in this way we can created repository classes automatically, unit of work properties and many more.

Comments

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 ...

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...

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 ...

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...

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...

Blazor 0.5.0 Interop JavaScript from C# and C# to JavaScript call

Blazor provides two-way communication from JS to C# and C# to JS which is called Interop. The version upgrade to Blazor 0.5.0 changed the approach in interactions between cshtml and JS files. The newer version simplifies JS calling by avoiding pre-registration of JS function. In this article, we would see how to call a JS method by passing multiple parameters from cshtml and parameterized call from JS to cshtml. The scenario that is used in this article has a Kendo AutoComplete to search book and populate information based on the selection. An example of a call to JS from cshtml await JSRuntime.Current.InvokeAsync<string>( "searchBook.Init", "#SearchTitle", new DotNetObjectRef(this)); Takeaways from the above example: - JSRuntime.Current give environment to execute out-process JS. - InvokeAsync is a function that would allow executing the JS function. - The searchBook.Init is a JS function call, we would see it in details in the second sec...

Channel, ChannelReader and ChannelWriter to manage data streams in multi-threading environment

I came across Channel class while working with SignalR which looks really interesting. By looking into NuGet packages ( https://www.nuget.org/packages/System.Threading.Channels ), it seems just 4 months old. The Channel class provides infrastructure to have multiple reads and write simuletensely through it's Reader and Writer properties. This is where it is handy in case of SignalR where data streaming needs to be done but is not just limited to that but wherever something needs to be read/write/combination of both in a multi-threading environment. In my case with SignalR, I had to stream stock data at a regular interval of time. public ChannelReader<StockData> StreamStock() { var channel = Channel.CreateUnbounded<StockData>(); _stockManager.OnStockData = stockData => { channel.Writer.TryWrite(stockData); }; return channel.Reader; } The SignalR keeps return type of ChannelReader<StockData> open so that whatev...

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...

A wrapper implementation for Kendo Grid usage

A wrapper implementation for any heavily used item is always a good practice. Whatever is not written by us and used at a lot of places should be wrapped within specific functionality to keep it future proof and easily changeable. This also encourages DRY principle to keep our common setting at a central place. Kendo UI items are enormous in configuration, one of an issue I find people keep repeating codes for Kendo Grid configuration. They have built very flexible system to have any configuration, but in most of the cases, we do not need all of those complicated configuration. We would try to see a simpler configuration of same. The actual core implementation is bit complex, but we do not have to bother about it once done since the focus is just on usage only. I recommend doing this practice for as simple as jQuery events, form handling or as simple as any notification system. This just won't make things simple but makes codes much more manageable, easy understand, read or open f...