Rendering Blazor components using HtmlRenderer

🚀 Rendering Blazor Components Dynamically with HtmlRenderer in .NET 8

A practical example using a generic component renderer

Source code available here:
👉 https://github.com/toreaurstadboss/BlazorIntroCourse/tree/main/Components/Demos/TemplatedComponents

Blazor has always been about component‑driven UI, but until .NET 8, components were tightly coupled to the Blazor runtime — either WebAssembly or Server. With the introduction of HtmlRenderer, that boundary disappears.

You can now render any .razor component into pure HTML on the server, without a browser, without WebAssembly, and without a running Blazor app. This opens up a whole new world of scenarios:

• Rendering components inside MVC, Razor Pages, or Minimal APIs
• Generating HTML for emails, PDFs, reports, or static site generation
• Using Blazor components as server‑side templates
• Building dynamic component renderers that choose components at runtime
• Running components in background services or unit tests

In this post, I’ll walk through a practical example: A generic Blazor component that uses HtmlRenderer to render any component dynamically, and a simple Bootstrap‑style Alert component to demonstrate how it works.

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🎯 Why HtmlRenderer Matters

Here’s the short version — arguments you can inform other developers why HtmlRenderer opens up so many possibilities for using Blazor components many places:

• Render Blazor components anywhere — MVC, Razor Pages, Minimal APIs, background jobs.
• Generate static HTML — perfect for emails, PDFs, SEO, caching, and static sites.
• Use Blazor components as templates — no need for Razor Views or TagHelpers.
• Full component lifecycle — DI, parameters, cascading values, child content all work.
• No browser required — everything runs server‑side.
• Dynamic component composition — choose components at runtime using generics.
• Great for testing — render components without a browser or JS runtime.

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🖼️ Diagram: How HtmlRenderer Works

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📦Sample Blazor component used | Alert.razor — A Simple Bootstrap‑Style Alert Component

<div 
    class=@($"alert {(IsDismissable ? "alert-dismissible fade show" : "")} alert-{AlertType.ToString().ToLower()}")
    role="alert">
    @if (IsDismissable)
    {
        <button type="button" class="btn-close" data-bs-dismiss="alert" aria-label="Close"></button>
    }
    @ChildContent
</div>

@code {

    [Parameter]
    public required RenderFragment ChildContent { get; set; } = @<b>Default message</b>;

    [Parameter]
    public bool IsDismissable { get; set; }

    [Parameter]
    public AlertTypeEnum AlertType { get; set; } = AlertTypeEnum.Success;

}

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🧩 The alert type enum | AlertTypeEnum.cs

namespace DependencyInjectionDemo.Components.Demos.TemplatedComponents
{
    public enum AlertTypeEnum
    {
        Primary,
        Secondary,
        Success,
        Danger,
        Warning,
        Info,
        Light,
        Dark
    }
}

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🧠 The Generic HTML Renderer Component | GenericHtmlRenderer.razor

@((MarkupString)RenderedHtml)

@typeparam TComponent

@code {
    [Parameter] public RenderFragment? ChildContent { get; set; }
    [Parameter] public Dictionary<string, object?> Parameters { get; set; } = new();

    [Inject] IServiceProvider ServiceProvider { get; set; } = default!;
    [Inject] ILoggerFactory LoggerFactory { get; set; } = default!;

    private string RenderedHtml { get; set; } = string.Empty;

    protected override async Task OnInitializedAsync()
    {
        if (ChildContent != null)
        {
            Parameters["ChildContent"] = ChildContent;
        }

        RenderedHtml = await RenderComponentAsync(Parameters);
    }

    private async Task<string> RenderComponentAsync(Dictionary<string, object?> parameters)
    {
        if (!typeof(IComponent).IsAssignableFrom(typeof(TComponent)))
        {
            throw new InvalidOperationException($"{typeof(TComponent).Name} is not a valid Blazor component.");
        }

        using var htmlRenderer = new HtmlRenderer(ServiceProvider, LoggerFactory);
        var parameterView = ParameterView.FromDictionary(parameters);

        var html = await htmlRenderer.Dispatcher.InvokeAsync(async () =>
        {
            var result = await htmlRenderer.RenderComponentAsync(typeof(TComponent), parameterView);
            return result.ToHtmlString();
        });

        return html;
    }
}

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🧪 Demo Page — Rendering Alerts Dynamically | GenericHtmlRendererDemo.razor

@page "/GenericHtmlRendererDemo"
@using BlazorIntroCourse.Components.Demos.TemplatedComponents

<h3>GenericHtmlRendererDemo - Dynamic Alert rendering</h3>

<h6>Here the parameters are set in code</h6>
<GenericHtmlRenderer TComponent="Alert"
                     ChildContent="alertContent"
                     Parameters="alternateAlertParameters" />

<h6>Here we use the ChildContent element to enter in the html</h6>
<GenericHtmlRenderer TComponent="Alert"
                     Parameters="alertParameters">
    <ChildContent>
        <text>This is the second alert</text>
    </ChildContent>                 
</GenericHtmlRenderer>

<h6>Here we use inline object initializer for parameters</h6>
<GenericHtmlRenderer TComponent="Alert"
                     Parameters="@(new Dictionary<string, object>{
    [ "AlertType" ] = AlertTypeEnum.Danger,
    [ "IsDismissable" ] = true
})">
    <ChildContent>
        <text>This is the third alert</text>
    </ChildContent>  
</GenericHtmlRenderer>

@code {

    private RenderFragment alertContent = @<text>This is the first Alert</text>;
    Dictionary<string, object?> alertParameters = new()
    {
        { "AlertType", AlertTypeEnum.Info}, 
        { "IsDismissable", true }
    };

    Dictionary<string, object?> alternateAlertParameters = new()
    {
        { "AlertType", AlertTypeEnum.Success }, 
        { "IsDismissable", true }
    };

}

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📘 Diagram: Where You Can Use HtmlRenderer

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🏁 Wrapping Up

HtmlRenderer in .NET 8 is one of those features that quietly unlocks a huge amount of flexibility. It turns Blazor components into universal UI building blocks that can be rendered:

• in a browser
• on the server
• inside MVC
• inside Razor Pages
• inside Minimal APIs
• inside background services
• inside unit tests
• or even at build time

The generic component renderer shown here is a concrete example of how powerful this can be — dynamic component rendering, runtime composition, and server‑side HTML generation all in one.

If you’re curious, you can explore the full source code here: (part of a larger repo I am looking into currently as a playground for misc Blazor functionality):
👉 https://github.com/toreaurstadboss/BlazorIntroCourse/tree/main/Components/Demos/TemplatedComponents

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