Introducing the Telerik UI for Blazor Early Preview, .NET UI components for the Blazor framework without legacy JavaScript dependencies. 

Progress Software and the Telerik brand has a long history of supporting the .NET community with products like Telerik UI for ASP.NET AJAX, UI for ASP.NET, and UI for ASP.NET Core. This is why we’re proud to announce the early preview release of Telerik UI for Blazor!

  1. What is Blazor
  2. What is Razor Components
  3. Blazor Recommended Reading
  4. Built from the Ground-Up - 100% Native .NET
  5. Experiment With Us
  6. Telerik UI for Blazor Early Preview

What is Blazor

Blazor is a new framework by the Microsoft ASP.NET team that introduces a next generation component model that allows developers to write Single Page Applications (SPA) without JavaScript. If Blazor sounds new to you that’s because it has only been in development less than a year, and as an experimental project. Initially the Blazor framework targeted the Mono WebAssembly runtime (the .NET runtime compiled to wasm), thus allowing .NET to run on the client’s browser inspiring the name “Blazor” (Browser + Razor).

In this configuration the application’s resources including .dll files are delivered to the client and executed the Mono WebAssembly runtime. While the WebAssembly deployment of Blazor is sill in active development a server-side deployment option was introduced called Razor Components.

Blazor Component Model

The Blazor component model is refreshingly simple in its design. Components can contain markup (HTML) and logic (C#) in a single Razor (cshtml) file. The component is capable of handling data binding, events, and dependency injection all without JavaScript.

The Counter Component below demonstrates the basic composition of a Blazor component.

The counter component uses a basic HTML button to increment a counter field which is displayed within a paragraph tag. Because Blazor operates as a single page application all of the interactions in the component happen on the client. Updates to the browser’s Document Object Model (DOM) are handled by the Blazor framework though data binding.

What is Razor Components

Recently Microsoft has announced plans to support the framework when running server-side in a mode called Razor Components. Even more recently, an announcement was made that the same component model will be backwards compatible with ASP.NET Core (MVC) and Razor Pages. All of these cutting edge news and bits dropping around Blazor has our team at Telerik excited for the future of ASP.NET development. Much like Blazor running on WebAssembly, Razor Components allows developers to write Single Page Applications (SPA) without JavaScript.

The key difference between Blazor and Razor Components is the way the application is deployed. Instead of Blazor running via WebAssembly on the client, the Blazor framework runs on the server as an executable. In this mode, ASP.NET Core hosts the application and provides a communication channel using SignalR technology. Using SignalR the application sends UI updates and receives changes and events as binary packets of data over a web socket connection. Since only the changes are sent over the connection, the payload is small and efficient.

Since Razor Components utilizes the Blazor framework, components can be used in both deployment types.

If all of this is new to you, and it’s most likely that it is, then we have some blog posts to catch you up on all things Blazor. The following articles should bring you up to speed, or if you’re biting your nails to check out what’s below, we’ve included the TLDR as well.


Razor Components, is what originally started as Blazor Server-Side in early 2018. Blazor is a .NET (SPA) framework that is generally associated with .NET running on Web Assembly. However, Blazor is capable of running under multiple scenarios including server-side as Razor Components.

  • Razor is a popular template markup syntax for .NET
  • (Browser + Razor) Blazor is a .NET based web framework which can run on the client using WebAssembly or as:
    • Razor Components: The Blazor framework running on the server via SignalR
    • Razor Components via “circuits” - Razor Components running in ASP.NET Core / Razor Pages
  • All Blazor hosting models, both client and server-side, utilize C# APIs instead of JavaScript
  • Razor Components is expected to ship in ASP.NET Core 3.0

Built from the Ground-Up - 100% Native .NET

Telerik UI for Blazor will not wrap existing jQuery/JavaScript products in C# and pretend it’s something new. With Telerik UI for Blazor we are starting from scratch and writing components with .NET whenever possible. Alternatively we could have decided to wrap existing jQuery components, as short-term path, however we feel that the wrapper programming model is a leaky abstraction that would “bleed back” into the .NET API layer. In addition, we feel that a native .NET approach is a long term investment that will fetch larger gains in the long run. Consider this a modern day tortoise vs. hare story.

We can’t express enough how important both the JavaScript and .NET ecosystems are to us. We have UI libraries for developers of all skill types, however a segment of .NET community has expressed the need for front-end web tooling that does not require JavaScript and we’re happy to have the opportunity to serve this community through Blazor.

Experiment With Us

Blazor is an exciting prospect for .NET developers because it allows us to create full-stack .NET web application. We have received countless feedback items asking for our support this next generation platform.

Initially we’re offering Telerik UI For Blazor as an early preview release. This development model closely resembles the effort being made by Microsoft with Blazor as we aim to release small sets of functionality in hopes to gain feedback and knowledge about how our customers use the product. During the experimental phase Telerik UI for Blazor will be a free trial for all and we hope that you will continue sharing with us your use cases, experience, road-blocks, and bugs.

After downloading Telerik UI for Blazor you will receive an email with instructions on how to share your feedback, wishes and Blazor experiments with us.

Telerik UI for Blazor Early Preview

The initial offering will be small with just a few popular UI components including the Data Grid, Tab Set, and Buttons. Through customer feedback we plan to expand the number of components and rage of APIs. We believe that building to our customers needs and recommendations is the path to success.


Since the ASP.NET Preview's are moving at a rapid place, it's best to update your bits. Make sure you're on the current version of Razor Components (server-side) and Blazor (client-side) since we'll be working with both. Detailed installation instructions for both frameworks can be found on the Blazor getting started page.

Also be sure that you have enabled the Telerik UI for Blazor free early preview. Even if you have previously enrolled in the preview you may need to revisit this page for the latest version to appear in your feed. With this free account you'll be able to add the Telerik NuGet Package Source


Installing Telerik UI for Blazor requires just a few simple steps. First we'll need to install the package binaries. We'll be using the Telerik NuGet Package Source to install the package. If you don't have the Telerik Package Source already please see the Prerequisites section above.

If you have multiple solutions in your project, install the package to the project which contains the "Pages" folder. These are the views for your application.

We can use the Package Manager dialog, command line, or directly edit the .csproj file of the application.


Telerik UI for Blazor Nuget

Command line

$ dotnet add package Telerik.UI.for.Blazor

Edit .csproj

<PackageReference Include="Telerik.UI.for.Blazor" Version="0.4.0" />

Once the Telerik UI for Blazor package has been installed, we'll need to make a reference to the components in the package. This will act as a global using statement for our application. Open the root _ViewImports file and add the @addTagHelper *, Telerik.Blazor directive.


@addTagHelper *,Telerik.Blazor

We also need to register the the library with dependency injection. This will resolve any dependencies needed by the components. In the same solution, open the Startup class and register the AddTelerikBlazor service.


Next we'll need to add the CSS theme files to the application. At the time of writing Telerik UI for Blazor supports three of the Kendo UI themes: Default, Bootstrap 4, and Material Design.

Grid themes

If you have multiple solutions in your project, find the project which contains the "wwwroot" folder. These are the static resources for your application. In the root of the project, add a file named libman.json. LibMan is a client-side library manager built into Visual Stuido (with CLI support) that will fetch static resources and save them to your project.

Add the following configuration to your libman.json file. Save the file and all three component themes will be copied to your wwwroot folder.

  "version": "1.0",
  "defaultProvider": "unpkg",
  "libraries": [
      "library": "@progress/kendo-theme-default@3.0.0",
      "destination": "wwwroot/css/kendo-themes/default",
      "files": [
      "library": "@progress/kendo-theme-bootstrap@3.0.0",
      "destination": "wwwroot/css/kendo-themes/bootstrap",
      "files": [
      "library": "@progress/kendo-theme-material@2.0.0",
      "destination": "wwwroot/css/kendo-themes/material",
      "files": [

With the themes installed, reference the desired theme from your application's index.html file.


    <!-- <link rel="stylesheet" href="/css/kendo-themes/material/dist/all.css" />
    <link rel="stylesheet" href="/css/kendo-themes/default/dist/all.css" /> -->
    <link rel="stylesheet" href="/css/kendo-themes/bootstrap/dist/all.css" />
<script src=""></script> </head>

Blazor (client-side operation)

Telerik UI for Blazor is compatible on the client, but currently has a known issue which requires disabling the Blazor IL Linker. Without digging into IL Linking too deep, the result of disabling it only results in a larger payload size. This is a temporary situation that will be resolved in later versions of the framework.

To disable IL Linker, open the .csproj file and add <BlazorLinkOnBuild>false</BlazorLinkOnBuild> to the top most property group.

    <!-- add the line below to disable IL Linker -->

That's it! Now we're ready to begin building Razor Components or Blazor applications using Telerik UI for Blazor. 

Blazor Data Grid

The Telerik UI for Blazor Data Grid has quite a few features in this preview. The data grid in this release is capable of: data binding, sorting, paging, themes, templates, and in-cell editing, which only supports int, string and DateTime fields.

Let’s see these features in action by replacing the hand coded table in the Fetch Data example with the Telerik Data Grid. First take a moment to run and explore the Fetch Data example at localhost/fetchdata.

Locate the code for Fetch Data under the /Pages folder. Replace the entire table element with a TelerikGrid component.

    <TelerikGrid Data=@forecasts Pageable=true PageSize=5 Sortable=true>
            <TelerikGridColumn Field=@nameof(WeatherForecast.Date)>
                    @($"{(context as WeatherForecast).Date:d}")
            <TelerikGridColumn Field=@nameof(WeatherForecast.TemperatureC)/>
            <TelerikGridColumn Field=@nameof(WeatherForecast.TemperatureF)/>
            <TelerikGridColumn Field=@nameof(WeatherForecast.Summary)/>

The TelerikGrid component binds the Data property to forecasts which is an array of the WeatherForecast object. The grid also has the Pageable, PageSize, and Sortable properties enabled. Inside of the TelerikGrid component, we define child components for each field we would like displayed in the grid. Because this is all C# code, we can set the Field property with C#'s nameof operator giving us type safety. In addition, templates can be used to display custom formats, images, and even other UI components. Here a template is used to format the Date field.

Blazor Tab Set

The other major component included in this release is the TelerikTabSet. The TelerikTabSet supports multiple tab positions: Top (default), Bottom, Left, and Right. We can use Blazor’s bind attribute to demonstrate the tab positions at run-time. Locate the index.cshtml page under the /pages folder. Replace the page’s content with the following code.

@using Telerik.Blazor.Components.TabStrip

<h1>Hello, world!</h1>
<select bind=@tabPosition>
  <option value=@TelerikTabPosition.Top>Top</option>
  <option value=@TelerikTabPosition.Left>Left</option>
  <option value=@TelerikTabPosition.Right>Right</option>
  <option value=@TelerikTabPosition.Bottom>Bottom</option>

<TelerikTabStrip TabPosition=@tabPosition>
  <TelerikTab Title="Sofia">
    <p>Sunny weather in Sofia</p>
  <TelerikTab Title="New York">
    <p>Partly Cloudy weather in New York</p>
  <TelerikTab Title="Paris">
    <p>Rainy weather in Paris</p>

@functions {
  TelerikTabPosition tabPosition = TelerikTabPosition.Top;

In this example we start by creating a simple select list element with all of the TelerikTabStrip position values, TelerikTabPosition.<value>. Most importantly, TelerikTabPosition is a standard C# enum type so we get strongly typed values and intellisense here. Next a TelerikTabStrip component is created with several TelerikTab components that display some weather forecast data. The TapPosition property is bound to both the select element and TelerikTabStrip through the a simple backing field tabPosition declared in @function.

Because select is using the bind attribute, it automatically updates the tabPosition value when the option is changed, this allows us to modify the position at run-time.


We’re excited to be part of the next generation of ASP.NET applications by supporting Blazor. Telerik UI for Blazor Early Preview is available for free today. The package currently includes Data Grid, Tab Set, and Button components written from the gound up to take advantage of Blazor without JavaScript dependencies (there’s no jQuery this time folks). Throughout the year Microsoft will be working on Blazor (aka Razor Components) as part of ASP.NET Core 3.0. We plan on keeping Telerik UI for Blazor up to date as the project progresses and look forward to hearing your feedback, see what you’ve built, and know what components you need for your next app.

Ed Charbeneau is a Developer Advocate for Telerik
About the Author

Ed Charbeneau

Ed Charbeneau is a web enthusiast, speaker, writer, design admirer, and Developer Advocate for Telerik. He has designed and developed web based applications for business, manufacturing, systems integration as well as customer facing websites. Ed enjoys geeking out to cool new tech, brainstorming about future technology, and admiring great design. Ed's latest projects can be found on GitHub.

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