---
title: "SchemaEnforcement source"
url: "https://nsta1.github.io/Orleans.Lattice/samples/SchemaEnforcement/source.html"
source: "https://github.com/NSTA1/Orleans.Lattice/tree/release/9.9/samples/SchemaEnforcement"
documents: "Orleans.Lattice 9.9.0 (release line 9.9)"
built: "2026-10-04"
all-pages: "https://nsta1.github.io/Orleans.Lattice/llms.txt"
---
# SchemaEnforcement source

Part of [Schema enforcement and versioning](README.md).

The source of the [SchemaEnforcement](https://github.com/NSTA1/Orleans.Lattice/tree/release/9.9/samples/SchemaEnforcement) sample.

## Program.cs

````csharp
using System.Text;
using Microsoft.Extensions.DependencyInjection;
using Microsoft.Extensions.Hosting;
using Microsoft.Extensions.Logging;
using Orleans.Hosting;
using Orleans.Lattice;
using Orleans.Lattice.Schema;

// ---------------------------------------------------------------------------
// SchemaEnforcement - server-side validation and per-value versioning.
//
// The core lattice stores every value as an opaque byte[] and attaches no
// schema to it. The companion Orleans.Lattice.Schema package adds two opt-in,
// composable capabilities:
//
//   1. Enforcement - a per-tree policy validates values written through the
//      tree's write operations. A non-compliant local write fails fast with
//      LatticeSchemaViolationException and is never persisted.
//   2. Versioning  - each value is stamped with a schema version; stale values
//      are upcast to the tree's current target version on read. Advancing the
//      target version is an admin action; existing values migrate lazily.
//
// This sample installs both on one silo, then exercises each in turn.
// ---------------------------------------------------------------------------

using var host = Host.CreateDefaultBuilder(args)
    .ConfigureLogging(logging =>
    {
        logging.ClearProviders();
        logging.SetMinimumLevel(LogLevel.None);
    })
    .UseOrleans(silo =>
    {
        silo.UseLocalhostClustering();
        silo.AddMemoryGrainStorageAsDefault();
        silo.UseInMemoryReminderService();
        silo.AddLattice((s, name) => s.AddMemoryGrainStorage(name));

        // Enforcement first, then versioning (versioning composes the concrete
        // enforcement write interceptor, so the order matters).
        silo.AddLatticeSchemaEnforcement();
        silo.AddLatticeSchemaVersioning(registry =>
        {
            registry.AddSchema(schemaId: 1, version: 1, name: "order");
            registry.AddSchema(schemaId: 1, version: 2, name: "order");

            // v1 -> v2 adds a default "status": "open" member.
            registry.AddUpcaster(
                schemaId: 1,
                fromVersion: 1,
                toVersion: 2,
                transform: LatticeValueTransform.Passthrough(
                    LatticeValueTransform.SetMember(
                        "status", LatticeValueTransform.Const(LatticeConstant.Text("open")))));
        });
    })
    .Build();

await host.StartAsync();
var grainFactory = host.Services.GetRequiredService<IGrainFactory>();
var schemaAdmin = host.Services.GetRequiredService<ILatticeSchemaAdmin>();
var versionAdmin = host.Services.GetRequiredService<ILatticeSchemaVersionAdmin>();

Console.WriteLine("== SchemaEnforcement sample ==");
Console.WriteLine();

// -- Part 1: enforcement ----------------------------------------------------

Console.WriteLine("Part 1: enforcement");
Console.WriteLine();

var orders = grainFactory.GetGrain<ILattice>("orders");

// Require every value written to "orders" to be well-formed JSON.
await schemaAdmin.SetPolicyAsync("orders", new LatticeSchemaPolicy(new[] { LatticeSchemaRule.Json() }));
Console.WriteLine("Installed a JSON policy on 'orders'.");

// A well-formed JSON value is accepted.
await orders.SetAsync("order:1", Encoding.UTF8.GetBytes("{\"id\":\"order:1\",\"quantity\":3}"));
Console.WriteLine("   accepted a well-formed JSON write.");

// A malformed value is rejected before it is persisted.
try
{
    await orders.SetAsync("order:2", Encoding.UTF8.GetBytes("not json at all"));
    Console.WriteLine("   ERROR: the malformed write was unexpectedly accepted.");
}
catch (LatticeSchemaViolationException ex)
{
    Console.WriteLine($"   rejected a malformed write: {ex.Message}");
}

// The rejected key was never stored.
var order2 = await orders.GetAsync("order:2");
Console.WriteLine($"   'order:2' is {(order2 is null ? "<not found>" : "present")} after the rejected write.");
Console.WriteLine();

// -- Part 2: versioning -----------------------------------------------------

Console.WriteLine("Part 2: versioning");
Console.WriteLine();

var catalog = grainFactory.GetGrain<ILattice>("catalog");

// Opt "catalog" in at schema 1, version 1; new writes are stamped v1.
await versionAdmin.SetVersionConfigAsync("catalog", new LatticeSchemaVersionConfig(schemaId: 1, targetVersion: 1));
await catalog.SetAsync("sku:42", Encoding.UTF8.GetBytes("{\"id\":\"sku:42\",\"quantity\":7}"));
Console.WriteLine("Wrote 'sku:42' as schema 1, version 1.");
Console.WriteLine($"   read at v1 target: {Decode(await catalog.GetAsync("sku:42"))}");

// Advance the target to v2. Existing v1 values upcast on the next read.
await versionAdmin.AdvanceTargetVersionAsync("catalog", newTargetVersion: 2);
Console.WriteLine("Advanced 'catalog' target version to 2.");
Console.WriteLine($"   read at v2 target: {Decode(await catalog.GetAsync("sku:42"))}");
Console.WriteLine("   -> the stored v1 value was upcast on read; 'status' appeared.");
Console.WriteLine();

Console.WriteLine("Done.");
await host.StopAsync();

static string Decode(byte[]? bytes) =>
    bytes is null ? "<not found>" : Encoding.UTF8.GetString(bytes);
````

## SchemaEnforcement.csproj

````xml
<Project Sdk="Microsoft.NET.Sdk">

  <PropertyGroup>
    <OutputType>Exe</OutputType>
    <TargetFramework>net10.0</TargetFramework>
    <ImplicitUsings>enable</ImplicitUsings>
    <Nullable>enable</Nullable>
    <RootNamespace>Orleans.Lattice.Samples.SchemaEnforcement</RootNamespace>
    <AssemblyName>Orleans.Lattice.Samples.SchemaEnforcement</AssemblyName>
    <IsPackable>false</IsPackable>
  </PropertyGroup>

  <ItemGroup>
    <PackageReference Include="Microsoft.Extensions.Hosting" Version="10.0.11" />
    <PackageReference Include="Microsoft.Orleans.Server" Version="10.2.2" />
  </ItemGroup>

  <ItemGroup>
    <ProjectReference Include="..\..\src\lattice\Orleans.Lattice.csproj" />
    <ProjectReference Include="..\..\src\lattice.schema\Orleans.Lattice.Schema.csproj" />
  </ItemGroup>

</Project>
````