How I embedded a Blazor Server admin portal into an ASP.NET Core app via NuGet
Hey r/csharp,
I wanted to share an architectural approach I've been working on — embedding a full Blazor Server UI as a NuGet library into an existing ASP.NET Core application.
The idea: instead of building reporting UI from scratch in every project, package the entire Blazor portal as a library that drops into any ASP.NET Core app with minimal configuration.
**The core challenge** was making Blazor Server work as an embedded library rather than a standalone app. The key pieces:
**1. Serving static assets from the library**
Blazor's static files (JS, CSS) need to be served from the host app. This works via embedded resources and a custom middleware that intercepts requests to `/admin.css`, `/admin.js` etc:
```csharp
app.UseStaticFiles();
// Host app serves the library's embedded assets
```
**2. Routing — MapFallbackToPage**
The admin portal lives at `/reportadmin` without conflicting with the host app's routes:
```csharp
app.MapFallbackToPage("/reportadmin/{**path}", "/_Host");
app.MapFallbackToPage("/reportadmin", "/_Host");
```
**3. Data provider pattern**
Instead of hardcoding data access, consumers implement an interface:
```csharp
public interface IReportDataProvider
{
string EntityName { get; }
string DisplayName { get; }
IReadOnlyList<ReportColumnDefinition> AvailableColumns { get; }
IReadOnlyList<ReportFilterDefinition> AvailableFilters { get; }
Task<ReportTable> GetDataAsync(ReportBuilderRequest request, CancellationToken ct = default);
Task<int> GetCountAsync(ReportBuilderRequest request, CancellationToken ct = default);
}
```
**4. PDF generation in Blazor Server context**
Playwright's `CreateAsync()` throws a `NullReferenceException` when called directly from Blazor Server's synchronization context. The fix is wrapping in `Task.Run`:
```csharp
var pdfBytes = await Task.Run(async () =>
{
using var playwright = await Playwright.CreateAsync();
await using var browser = await playwright.Chromium.LaunchAsync(...);
// ...
}, ct);
```
**5. Offline license validation**
JWT tokens signed with RSA private key, validated against an embedded public key — no network calls, works air-gapped:
```csharp
var rsa = RSA.Create();
rsa.ImportFromPem(embeddedPublicKey);
var validationParams = new TokenValidationParameters
{
IssuerSigningKey = new RsaSecurityKey(rsa),
ValidateIssuerSigningKey = true,
// ...
};
```
The result is a library that adds a full reporting portal to any ASP.NET Core app — report builder, PDF/Excel export, scheduler, audit trail — without requiring a separate server or database beyond a local SQLite file.
Happy to go deeper on any of these pieces if anyone's interested.
**Live demo** if you want to see the end result: https://reporting.screamcode.com/reportadmin