An ASP.NET MVC view engine supplementing Razor with React/JSX style component composability allowing you to do this:

<component-tabcontainer>
    <component-tab active="@true">
        Tab 1
    </component-tab>
    <component-tab active="@false">
        Tab 2
    </component-tab>
    <component-tab active="@false">
        Tab 3
    </component-tab>
</component-tabcontainer>

When you create these partials:

<div class="tabcontainer">
    @Model.children
</div>

<div class="tab@(Model.active ? " active" : "")">
    <a>
        @Model.children
    </a>
</div>

In a .NET framework web application in your Global.asax.cs file, add:

RazorXViewEngine.Initialize();

I've been writing React applications using JSX/TSX for a while now and appreciate the composability of creating reusable components with it.

With ASP.NET / Razor I have come to find the current methods of creating reusable presentational components lacking:

• Partials - Can't wrap other content unless you specifically create start and end partials and passing properties via the object model can be cumbersome.

• HTMLHelpers / TagHelpers - You have to write C# code which renders markup. Not to mention you can't use tag helpers in ASP.NET MVC (non-core).

• @helper - Doesn't deal with composability of multiple helpers in a nice way.

In a nutshell cshtml files are pre-processed with a VirtualFileProvider meaning the resulting file presented to the default Razor view engine is a cshtml file with 100% valid Razor syntax. The preprocessing carried out is as follows:

• A tag formed with the name component-xxx will be processed into a @Html.Partial("xxx").
• If the tag is not self closing there will be 2 @Html.Partial() references for the start and end passing a property to determine if the partial should render the top or bottom portion of markup.
• All tag attributes are added to a dynamic object and passed as the model to the partial.
• If a partial contains @Model.children it will automatically split by the view engine to conditionally render the top or bottom portion of the markup based on property in the model.

Apart from the special component- tag the rest of the cshtml file is rendered by the default Razor view engine allowing you to use expressions and constructs as you normally would:

<component-boxout classname="my-boxout" type="@BoxoutType.Bordered">

    Lorem ipsum dolor sit amet, consectetur adipiscing elit. Pellentesque
    vitae purus id urna ornare convallis. Mauris ac cursus tortor. Phasellus
    pharetra lacus a nunc eleifend aliquam.

    <component-cardcontainer size="@CardSize.Third">

        @foreach (var idx in Enumerable.Range(1, 3))
        {
            <text>
                <component-card>
                    Lorem ipsum dolor sit amet, consectetur adipiscing elit. Pellentesque
                    vitae purus id urna ornare convallis. Mauris ac cursus tortor. Phasellus
                    pharetra lacus a nunc eleifend aliquam.
                </component-card>
            </text>
        }

    </component-cardcontainer>

</component-boxout>

• Less naive preprocessor moving from Regex to Razor syntax tree parser
• Property validation / intellisense
• Precompiled Razor views
• ASP.NET Core implementation

The work here is very experimental, work in progress and un-tested at this moment. Treat it more as a proof of concept and use at your own risk.