Skip to main content

Dynamic Data Binding Of Email Body Template Using .NET Core Razor Library

In general, there are two most common approaches to build an email template like:
  • System.Text.StringBuilder using this we generate template by appending n-number of strings. This approach is hard to maintain, can not do code debug, etc.
  • Another approach is like storing the entire email template in the database, where the template contains a placeholder to be replaced with dynamic data. Compare to the StringBuilder approach, the preferring database will make code Maintainance easy. But in this approach also debug code is hard.

What Kind Of Solution Razor Library Provides?:

Razor Library is a .Net Standard Library that has an inbuild razor engine where we can create Razor Page, MVC Views. It works as similar to MVC Views or Razor Pages where generate pages with Model binding.

So by using the Razor Library, we need to create a custom provider Razor Engine where we can fetch the Html of the page render using Model binding. So in this approach, we create Mvc View or Razor Page (.cshtml), to these pages we need to pass our required model for data binding. After successfully binding dynamic data we need to fetch *.cshtml content as a string to send as email body template.

This approach benefits us like easy code maintenance, good to debug the code like the normal MVC View, or Razor Page.

Create A .Net Core MVC Application:

Let's create a sample MVC application to get hands-on experience on this Dynamic Email Body Template creation.

OverView On Email Body With StringBuilder:

Note:
Skip this StringBuilder overview section if you have prior knowledge on email body template creation. The purpose of the section to give basic understanding on one of the old technique to those who doesn't have any knowledge on email body generation.
Let's create a sample email body using StringBuilder. Now add a new action method in HomeController.cs as below
Controllers/HomeController.cs:
[HttpGet]
[Route("email-body")]
public IActionResult EmailBody()
{
	string imageUrl = "https://localhost:5001/img/profile.webp";
	string firstName = "Naveen";
	string secondName = "bommidi";
	StringBuilder sb = new StringBuilder();
	sb.AppendFormat("<div class='row'>");
	sb.AppendFormat("<div class='col-sm-4'>");
	sb.AppendFormat("<div class='card'>");
	sb.AppendFormat("<img src='{0}' class='card-img-top'>", imageUrl);
	sb.AppendFormat("<div class='card-body'>");
	sb.AppendFormat("<h4 Card-title>{0} {1}</h4>", new object[] { firstName, secondName });
	sb.AppendFormat("</div>");
	sb.AppendFormat("</div>");
	sb.AppendFormat("</div>");
	sb.AppendFormat("</div>");

	string emailBody = sb.ToString();

	// write your logic to sending email

	return View("emailPreview",emailBody);
}
  • #L5,6,7 these lines show the data that need to bind to the email body template.
  • #L8 initialized StringBuilder object.
  • #L20 Convert entire StringBuilder object to normal string
  • #L22 comment shows where we need to implement email sending logic which not part of our topic.
  • #L24 we sending email body to *.cshtml file for preview the email output(it is development time code never do it in production)
  • From this sample code, we can understand this approach is hard to maintain, and updating any changes to the template will be not so easy.
To test or preview the email body(at the time of development) add the following code to emailPreview.cshtml page.
Views/Home/emailPreview.cshtml:
@model string

@Html.Raw(Model)

Add Razor Library:

Now let's explore the Razor library technique to create an email body in a more efficient way.

Let's select to add a Razor Class Library template.
After adding the Razor Class Library project structure looks as follows.

Add Email Body Html To View With Model Binding:

In the Razor Class Library template, we need to create views for email HTML body with dynamic binding. So let's store all our email view template inside the Areas(default framework folder).
Let's first create a model class for model binding in our email body template view files. Let's add the following sample model in Razor Class Library.
Models/Profile.cs:(Razor Class Library Project template)
namespace RazorLib.Models
{
    public class Profile
    {
        public string AvatarLink { get; set; }
        public string FirstName { get; set; }
        public string LastName { get; set; }
    }
}
Now add View with model binding in Razor Class Library.
Areas/MyFeature/Views/Profile/ProfileEmailBody.cshtml:(Razor Class Library)
@model RazorLib.Models.Profile

<div class="row">
    <div class="col-sm-4">
        <div class="card">
            <img src="@Model.AvatarLink" class="card-img-top">
            <div class="card-body">
                <h4 Card-title>@Model.FirstName @Model.LastName</h4>
            </div>
        </div>
    </div>
</div>
Now we have created Html Body inside View page, next, we need to implement a custom Razor Engine to read the razor views.

Custom Razor View Engine:

Now to execute the Views with Model binding and then to fetch Html output, we need to implement a custom Razor View Engine. This custom Razor View Engine exactly works like default view engine works in MVC or Razor Page .Net Core Framework template application. This is like creating a Razor View Engine explicitly in our Razor Class Library.

Let's implement a Custom Razor View Engine by injecting necessary services into it like below.
Services/CustomRazorEngine.cs:(Razor Class Library):
using Microsoft.AspNetCore.Mvc.Razor;
using Microsoft.AspNetCore.Mvc.ViewFeatures;
using System;

namespace RazorLib.Services
{
    public class CustomRazorEngine
    {
        private readonly IRazorViewEngine _razorViewEngine;
        private readonly ITempDataProvider _tempDataProvider;
        private readonly IServiceProvider _serviceProvider;
        public CustomRazorEngine(
            IRazorViewEngine razorViewEngine,
            ITempDataProvider tempDataProvider,
            IServiceProvider serviceProvider
            )
        {
            _razorViewEngine = razorViewEngine;
            _tempDataProvider = tempDataProvider;
            _serviceProvider = serviceProvider;
        }
    }
}
  • Microsoft.AspNetCore.Mvc.Razor.IRazorViewEngine - used to render the pages that use razor syntax.
  • Microsoft.AspNetCore.Mvc.ViewFeatures.ITempDataProvider - temporary storage memory for subsequent request.
  • System.IServiceProvider - provider for creating instances.
Razor View Engine must identify the required view page that needs to be rendered. So let's implement a new private method in our CustomRazorEngine class as below.
Services/CustomRazorEngine.cs:
private IView FindView(string ViewName)
{
	ViewEngineResult viewResult = _razorViewEngine.GetView(executingFilePath: null, viewPath: ViewName, isMainPage: true);
	if (viewResult.Success)
	{
		return viewResult.View;
	}
	throw new Exception("Invalid View Path");
}
  • #L1 this line show private method returns an IView type and this method expecting input parameter of the View name. Absolute file path included along with view name as an input parameter. If you want you can specify different parameters like one for view name and another for view absolute path.
  • #L3 Microsoft.AspNetCore.Mvc.Razor.IRazorViewEngine.GetView() - this method expecting 3 parameters. the first parameter like an absolute path to the view and it set null value in our implementation since we pass full absolute path along with view name. The second parameter expects either only view name or absolute path along with view name.
  • #L4, L6 If our engine able to find the expected view page it will be returning as output.
  • #L8 If our razor engine unable to find view then throw a custom exception like above code snippet.
Now implement a private method that creates basic Microsoft.AspNetCore.Mvc.ActionContext instance as below.
Services/CustomRazorEngine.cs:
private ActionContext GetContext()
{
	var httpContext = new DefaultHttpContext();
	httpContext.RequestServices = _serviceProvider;
	return new ActionContext(httpContext, new RouteData(), new ActionDescriptor());
}
In a normal web request for MVC or Razor Page Microsoft.AspNetCore.Mvc.ActionContext will be created by the framework. Since we are using Custom Razor View Engine we need to create a basic instance of Microsoft.AspNetCore.Mvc.ActionContext which some default values like HttpContex, RouteData and ActionDescriptor.

Let's start implementing how our custom Razor View Engine outputs the Html as below.
Services/CustomRazorEngine.cs:
public async Task<string> RazorViewToHtmlAsync<TModel>(string viewName, TModel model)
{
	var actionContext = GetContext();
	var view = FindView(viewName);

	using(var output = new StringWriter())
	{
		var viewContext = new ViewContext(
			actionContext: actionContext,
			view: view,
			viewData: new ViewDataDictionary<TModel>(
				metadataProvider: new EmptyModelMetadataProvider(),
				modelState: new ModelStateDictionary()
				)
			{
				Model = model
			},
			tempData: new TempDataDictionary(actionContext.HttpContext, _tempDataProvider),
			writer: output,
			htmlHelperOptions: new HtmlHelperOptions()
			);
		await view.RenderAsync(viewContext);
		return output.ToString();
	}
}
  • #L6 using System.Io.StringWriter stream to capture the rendered view HTML content
  • #L8 Microsoft.AspNetCore.Mvc.Rendering.ViewContext instance is the triggering point where it renders a View or Razor Page with model binding and writes the generated Html as a stream to System.Io.StringWriter.
  • #L10 view to be rendered.
  • #L16 view model.
  • #L19 Html content stream wirter.
Finally, custom Razor View Engine implementation looks as below.
Services/ICustomRazorEngine:
using System.Threading.Tasks;

namespace RazorLib.Services
{
    public interface ICustomRazorEngine
    {
        Task<string> RazorViewToHtmlAsync<TModel>(string viewName, TModel model);
    }
}
Services/CustomRazorEngine: 
using Microsoft.AspNetCore.Http;
using Microsoft.AspNetCore.Mvc;
using Microsoft.AspNetCore.Mvc.Abstractions;
using Microsoft.AspNetCore.Mvc.ModelBinding;
using Microsoft.AspNetCore.Mvc.Razor;
using Microsoft.AspNetCore.Mvc.Rendering;
using Microsoft.AspNetCore.Mvc.ViewEngines;
using Microsoft.AspNetCore.Mvc.ViewFeatures;
using Microsoft.AspNetCore.Routing;
using System;
using System.IO;
using System.Threading.Tasks;

namespace RazorLib.Services
{
    public class CustomRazorEngine: ICustomRazorEngine
    {
        private readonly IRazorViewEngine _razorViewEngine;
        private readonly ITempDataProvider _tempDataProvider;
        private readonly IServiceProvider _serviceProvider;
        public CustomRazorEngine(
            IRazorViewEngine razorViewEngine,
            ITempDataProvider tempDataProvider,
            IServiceProvider serviceProvider
            )
        {
            _razorViewEngine = razorViewEngine;
            _tempDataProvider = tempDataProvider;
            _serviceProvider = serviceProvider;
        }

        private IView FindView(string ViewName)
        {
            ViewEngineResult viewResult = _razorViewEngine.GetView(executingFilePath: null, viewPath: ViewName, isMainPage: true);
            if (viewResult.Success)
            {
                return viewResult.View;
            }
            throw new Exception("Invalid View Path");
        }

        private ActionContext GetContext()
        {
            var httpContext = new DefaultHttpContext();
            httpContext.RequestServices = _serviceProvider;
            return new ActionContext(httpContext, new RouteData(), new ActionDescriptor());
        }

        public async Task<string> RazorViewToHtmlAsync<TModel>(string viewName, TModel model)
        {
            var actionContext = GetContext();
            var view = FindView(viewName);

            using(var output = new StringWriter())
            {
                var viewContext = new ViewContext(
                    actionContext: actionContext,
                    view: view,
                    viewData: new ViewDataDictionary<TModel>(
                        metadataProvider: new EmptyModelMetadataProvider(),
                        modelState: new ModelStateDictionary()
                        )
                    {
                        Model = model
                    },
                    tempData: new TempDataDictionary(actionContext.HttpContext, _tempDataProvider),
                    writer: output,
                    htmlHelperOptions: new HtmlHelperOptions()
                    );
                await view.RenderAsync(viewContext);
                return output.ToString();
            }
        }
    }
}

Integrate Razor Class Library Into MVC Application:

Razor Class Library reference into MVC application as below.

Now register our custom razor view engine provider in the ConfigureServices method in Startup.cs file in our MVC application as below.
Startup.cs:
public void ConfigureServices(IServiceCollection services)
{
  //existing code hidden for display purpose 
  services.AddScoped<ICustomRazorEngine, CustomRazorEngine>();
}
Now inject custom razor view engine provider into HomeController.cs as follow.
Controllers/HomeController.cs:
using RazorLib.Services;

namespace EmailTemplate.MVC.Controllers
{
    public class HomeController : Controller
    {
        private readonly ICustomRazorEngine _customRazorEngine;

        public HomeController(ICustomRazorEngine customRazorEngine)
        {
            _customRazorEngine = customRazorEngine;
        }
    }
}

Update MVC Action Method To Generate Email Body:

Implement an action method to consume the custom razor engine provider. Need to specify the view page path and view model for data binding to custom razor engine provider.
Controllers/HomeController.cs:
[HttpGet]
[Route("email-body")]
public async Task<IActionResult> EmailBody()
{
	var profile = new Profile
	{
		AvatarLink = "https://localhost:5001/img/profile.webp",
		FirstName = "Naveen",
		LastName = "Bommidi"
	};

	string emailBody = await _customRazorEngine
		.RazorViewToHtmlAsync<Profile>("Areas/MyFeature/Views/Profile/ProfileEmailBody.cshtml", profile);

	// write your logic to sending email

	return View("emailPreview",emailBody);
}
  • #L5 view model created
  • #L12,13 view path and view model are passing as input parameters to the custom razor view engine provider.
  • #L15 comment represents need to configure email sending logic
  • #L17 is an optional line of code used to preview the email body at the time of development.
Html output preview:-

That's all about dynamic data binding of email body template using .NET Core razor library in an efficient approach.

Support Me!
Buy Me A Coffee PayPal Me 

Wrapping Up:

Hopefully, I think this article delivered some useful information about the Email Body Template Generation Using .Net Core Razor Library. I love to have your feedback, suggestions, and better techniques in the comment section below.

Follow Me:

Labels:

Comments

Post a Comment

Popular posts from this blog

.NET6 Web API CRUD Operation With Entity Framework Core

In this article, we are going to do a small demo on AspNetCore 6 Web API CRUD operations. What Is Web API: Web API is a framework for building HTTP services that can be accessed from any client like browser, mobile devices, desktop apps. In simple terminology API(Application Programming Interface) means an interface module that contains a programming function that can be requested via HTTP calls to save or fetch the data for their respective clients. Some of the key characteristics of API: Supports HTTP verbs like 'GET', 'POST', 'PUT', 'DELETE', etc. Supports default responses like 'XML' and 'JSON'. Also can define custom responses. Supports self-hosting or individual hosting, so that all different kinds of apps can consume it. Authentication and Authorization are easy to implement. The ideal platform to build REST full services. Create A .NET6 Web API Application: Let's create a .Net6 Web API sample application to accomplish our
6 comments
Read more

Angular 14 Reactive Forms Example

In this article, we will explore the Angular(14) reactive forms with an example. Reactive Forms: Angular reactive forms support model-driven techniques to handle the form's input values. The reactive forms state is immutable, any form filed change creates a new state for the form. Reactive forms are built around observable streams, where form inputs and values are provided as streams of input values, which can be accessed synchronously. Some key notations that involve in reactive forms are like: FormControl - each input element in the form is 'FormControl'. The 'FormControl' tracks the value and validation status of form fields. FormGroup - Track the value and validate the state of the group of 'FormControl'. FormBuilder - Angular service which can be used to create the 'FormGroup' or FormControl instance quickly. Form Array - That can hold infinite form control, this helps to create dynamic forms. Create An Angular(14) Application: Let'
3 comments
Read more

Part-1 Angular JWT Authentication Using HTTP Only Cookie[Angular V13]

In this article, we are going to implement a sample angular application authentication using HTTP only cookie that contains a JWT token. HTTP Only JWT Cookie: In a SPA(Single Page Application) Authentication JWT token either can be stored in browser 'LocalStorage' or in 'Cookie'. Storing JWT token inside of the cookie then the cookie should be HTTP Only. The HTTP-Only cookie nature is that it will be only accessible by the server application. Client apps like javascript-based apps can't access the HTTP-Only cookie. So if we use authentication with HTTP only JWT cookie then we no need to implement custom logic like adding authorization header or storing token data, etc at our client application. Because once the user authenticated cookie will be automatically sent to the server by the browser on every API call. Authentication API: To implement JWT cookie authentication we need to set up an API. For that, I had created a mock authentication API(Using the NestJS Se
Post a Comment
Read more

Unit Testing Asp.NetCore Web API Using xUnit[.NET6]

In this article, we are going to write test cases to an Asp.NetCore Web API(.NET6) application using the xUnit. xUnit For .NET: The xUnit for .Net is a free, open-source, community-focused unit testing tool for .NET applications. By default .Net also provides a xUnit project template to implement test cases. Unit test cases build upon the 'AAA' formula that means 'Arrange', 'Act' and 'Assert' Arrange - Declaring variables, objects, instantiating mocks, etc. Act - Calling or invoking the method that needs to be tested. Assert - The assert ensures that code behaves as expected means yielding expected output. Create An API And Unit Test Projects: Let's create a .Net6 Web API and xUnit sample applications to accomplish our demo. We can use either Visual Studio 2022 or Visual Studio Code(using .NET CLI commands) to create any.Net6 application. For this demo, I'm using the 'Visual Studio Code'(using the .NET CLI command) editor. Create a fo
6 comments
Read more

A Small Guide On NestJS Queues

NestJS Application Queues helps to deal with application scaling and performance challenges. When To Use Queues?: API request that mostly involves in time taking operations like CPU bound operation, doing them synchronously which will result in thread blocking. So to avoid these issues, it is an appropriate way to make the CPU-bound operation separate background job.  In nestjs one of the best solutions for these kinds of tasks is to implement the Queues. For queueing mechanism in the nestjs application most recommended library is '@nestjs/bull'(Bull is nodejs queue library). The 'Bull' depends on Redis cache for data storage like a job. So in this queueing technique, we will create services like 'Producer' and 'Consumer'. The 'Producer' is used to push our jobs into the Redis stores. The consumer will read those jobs(eg: CPU Bound Operations) and process them. So by using this queues technique user requests processed very fastly because actually
7 comments
Read more

Angular 14 State Management CRUD Example With NgRx(14)

In this article, we are going to implement the Angular(14) state management CRUD example with NgRx(14) NgRx Store For State Management: In an angular application to share consistent data between multiple components, we use NgRx state management. Using NgRx state helps to avoid unwanted API calls, easy to maintain consistent data, etc. The main building blocks for the NgRx store are: Actions - NgRx actions represents event to trigger the reducers to save the data into the stores. Reducer - Reducer's pure function, which is used to create a new state on data change. Store - The store is the model or entity that holds the data. Selector - Selector to fetch the slices of data from the store to angular components. Effects - Effects deals with external network calls like API. The effect gets executed based the action performed Ngrx State Management flow: The angular component needs data for binding.  So angular component calls an action that is responsible for invoking the API call.  Aft
7 comments
Read more

Usage Of CancellationToken In Asp.Net Core Applications

When To Use CancellationToken?: In a web application request abortion or orphan, requests are quite common. On users disconnected by network interruption or navigating between multiple pages before proper response or closing of the browser, tabs make the request aborted or orphan. An orphan request can't deliver a response to the client, but it will execute all steps(like database calls, HTTP calls, etc) at the server. Complete execution of an orphan request at the server might not be a problem generally if at all requests need to work on time taking a job at the server in those cases might be nice to terminate the execution immediately. So CancellationToken can be used to terminate a request execution at the server immediately once the request is aborted or orphan. Here we are going to see some sample code snippets about implementing a CancellationToken for Entity FrameworkCore, Dapper ORM, and HttpClient calls in Asp.NetCore MVC application. Note: The sample codes I will show in
2 comments
Read more

Blazor WebAssembly Custom Authentication From Scratch

In this article, we are going to explore and implement custom authentication from the scratch. In this sample, we will use JWT authentication for user authentication. Main Building Blocks Of Blazor WebAssembly Authentication: The core concepts of blazor webassembly authentication are: AuthenticationStateProvider Service AuthorizeView Component Task<AuthenticationState> Cascading Property CascadingAuthenticationState Component AuthorizeRouteView Component AuthenticationStateProvider Service - this provider holds the authentication information about the login user. The 'GetAuthenticationStateAsync()' method in the Authentication state provider returns user AuthenticationState. The 'NotifyAuthenticationStateChaged()' to notify the latest user information within the components which using this AuthenticationStateProvider. AuthorizeView Component - displays different content depending on the user authorization state. This component uses the AuthenticationStateProvider
6 comments
Read more

How Response Caching Works In Asp.Net Core

What Is Response Caching?: Response Caching means storing of response output and using stored response until it's under it's the expiration time. Response Caching approach cuts down some requests to the server and also reduces some workload on the server. Response Caching Headers: Response Caching carried out by the few Http based headers information between client and server. Main Response Caching Headers are like below Cache-Control Pragma Vary Cache-Control Header: Cache-Control header is the main header type for the response caching. Cache-Control will be decorated with the following directives. public - this directive indicates any cache may store the response. private - this directive allows to store response with respect to a single user and can't be stored with shared cache stores. max-age - this directive represents a time to hold a response in the cache. no-cache - this directive represents no storing of response and always fetch the fr
Post a Comment
Read more

Angular 14 Crud Example

In this article, we will implement CRUD operation in the Angular 14 application. Angular: Angular is a framework that can be used to build a single-page application. Angular applications are built with components that make our code simple and clean. Angular components compose of 3 files like TypeScript File(*.ts), Html File(*.html), CSS File(*.cs) Components typescript file and HTML file support 2-way binding which means data flow is bi-directional Component typescript file listens for all HTML events from the HTML file. Create Angular(14) Application: Let's create an Angular(14) application to begin our sample. Make sure to install the Angular CLI tool into our local machine because it provides easy CLI commands to play with the angular application. Command To Install Angular CLI npm install -g @angular/cli Run the below command to create the angular application. Command To Create Angular Application ng new name_of_your_app Note: While creating the app, you will see a noti
4 comments
Read more