# Host asset library with ASP.NET Core: file attachments

## Summary
Deploy a asset library built with ASP.NET Core on Ample using the browser file uploads pattern. Compute runs the app in an isolated microVM behind a public HTTPS URL, a managed PostgreSQL 16 database is auto-provisioned and injected as DATABASE_URL, a private S3-compatible bucket holds objects with credentials delivered as encrypted environment variables. Verified on ASP.NET Core: content-type and size validation that rejects disallowed files, an object written to a private bucket and a row linking the record to the object key (reject=ok upload=ok linked=ok). Not separately tested: your upload UI, allowed types, size limits and virus scanning; treat the asset library-specific behavior as your application code.

## Infrastructure requirements

- **Compute:** verified (Apps run in isolated x86_64 Firecracker microVMs that auto-pause when idle and wake on request; sizes are the priced VM sizes.)
- **Postgres:** verified (Managed PostgreSQL 16 runs in its own microVM and is auto-provisioned when an app needs a database and no DATABASE_URL is supplied.)
- **S3-compatible object storage:** verified (Buckets are S3-compatible with issued credentials; PutObject and GetObject are verified by canary. Other S3 operations are not verified.)

## Prerequisites

- A ASP.NET Core project that builds and starts with the documented commands (dotnet publish -c Release -o out in the builder, then dotnet <entry>.dll on the dotnet-10 template with ASPNETCORE_URLS bound to PORT)
- A PostgreSQL driver reading DATABASE_URL at runtime (auto-provisioned when omitted, or supplied with --env)
- A bucket from `ample bucket create` with its credentials passed as encrypted S3_* environment variables
- An Ample account token with servers:write, databases:read, buckets:read

## Exact tested configuration

- **template:** `dotnet-10`
- **runtime:** `dotnet`
- **size:** `s-1vcpu-1gb`
- **build:** `dotnet publish -c Release -o out`
- **start:** `ASPNETCORE_URLS=http://0.0.0.0:$PORT dotnet out/$(basename $(ls out/*.runtimeconfig.json | head -n 1) .runtimeconfig.json).dll`

## Steps

1. **Build and start.** dotnet publish -c Release -o out in the builder, then dotnet <entry>.dll on the dotnet-10 template with ASPNETCORE_URLS bound to PORT. The server must bind 0.0.0.0 on PORT.
2. **Implement the pattern on PostgreSQL.** The fixture's module implements browser file uploads: content-type and size validation that rejects disallowed files, an object written to a private bucket and a row linking the record to the object key (reject=ok upload=ok linked=ok). Copy the approach into your schema; keep migrations idempotent and run them with --release-command.
3. **Wire object storage.** Create the bucket(s), then pass endpoint, region, bucket and keys as --env values. Use path-style addressing. Keep private data in an unpublished bucket.
4. **Deploy.** Run the synchronous deploy once and read the result (exit 0 live, 1 failed, 2 blocked). Re-running with no change is a no-op.
   ```
   ample deploy . --name <app-name> --public --env S3_ENDPOINT=... --env S3_REGION=... --env S3_BUCKET=... --env S3_ACCESS_KEY_ID=... --env S3_SECRET_ACCESS_KEY=...
   ```
5. **Verify.** Fetch the live URL and the pattern self-test route(s) (/p/browser-file-uploads) from the example; then run your own checks. On failure read `ample logs <deployment_id> --kind build` then `--kind runtime`.
   ```
   ample logs <deployment_id> --kind build
   ```

## Tested examples

- **ASP.NET Core pattern fixture** (tests/deploy-canaries/asp-net-core-patterns): Multi-pattern ASP.NET Core app whose browser file uploads module was checked live; the module is under tests/deploy-canaries/_pattern-modules.

## Success checks

- app responds on its public URL (`/` on the live URL, expect ample canary asp net core patterns)
- browser-file-uploads self-test (`/p/browser-file-uploads` on the live URL, expect reject=ok upload=ok linked=ok)

## Limitations

- Verified on the dotnet-10 template at s-1vcpu-1gb with the example fixture; other sizes, templates and ASP.NET Core major versions are not verified.
- The asset library itself (your upload UI, allowed types, size limits and virus scanning) is application code and was not separately tested; the pattern checks are what was verified.
- Region, compliance attestations and request-duration limits are unknown and not claimed.
- Apps auto-pause when idle and wake on the next request; always-on is an operator setting, not a plan feature.
- Managed PostgreSQL 16 only; extensions, connection limits and backup or restore procedures are not verified; apps and their databases are placed together.
- PutObject and GetObject with path-style addressing are verified; multipart upload, listing, presigned URLs and lifecycle rules are not.

## Cost estimate

Estimated 10.00 USD per month (size prices from pricing.toml at build revision a1b8c38919e59cd035ebabaced73cf84ece24371).
- app server x1 `s-1vcpu-1gb`: 5.00 USD
- managed PostgreSQL database x1 `s-1vcpu-1gb`: 5.00 USD

## Verification evidence

- canary_run on 2026-09-21T01:15:54Z: ASP.NET Core pattern fixture deployed on Ample (dotnet publish -c Release -o out in the builder, then dotnet <entry>.dll on the dotnet-10 template with ASPNETCORE_URLS bound to PORT); checks passed for browser-file-uploads and configuration-secrets. Pattern proof: content-type and size validation that rejects disallowed files, an object written to a private bucket and a row linking the record to the object key (reject=ok upload=ok linked=ok). (expires 2027-03-20T01:15:54Z)  
- canary_run on 2026-09-20T23:34:47Z: The same ASP.NET Core app deployed with a --release-command migration; the marker it created was readable after activation. (expires 2027-03-19T23:34:47Z)

Last verified: 2026-09-21T01:15:54Z

## Execution binding
MCP tool `ample_deploy`, schema hash `876465fce906da0c` observed 2026-09-21T03:19:59.461917+00:00 at revision `49962bcade4f`, binding state `current`, required scopes: servers:write, databases:read, buckets:read.