Write a Command Handler

A command handler implements ICommandHandler<TCommand> (no result) or IQueryHandler<TCommand, TResult> (the unified interface that also handles ICommand<T>). Stratara discovers them via AddCommandHandlersFromAssemblyContaining<T>().

Choose the command shape

Scenario	Marker	Routing
Mutation without result, fire-and-forget	`ICommand`	`ICommandOutboxDispatcher` (async via outbox)
Mutation with synchronous result (e.g. setup, "create-and-return-id" flows)	`ICommand<TResult>`	`IMediator` (in-process)
Mutation that destroys infrastructure (drop outbox, recreate write-store)	`ICommand<TResult>`	`IMediator` (must stay in-process)
Mutation that signals process-local state	`ICommand`	`IMediator` (in-process)
Read	`IQuery<TResult>`	`IMediator`

See Routing Conventions for the full table.

Define the command + handler

using Stratara.Abstractions.Mediator;

public sealed record DepositCommand(Guid AccountId, decimal Amount) : ICommand;

public sealed class DepositHandler(IAccountRepository repo) : ICommandHandler<DepositCommand>
{
    public async Task HandleAsync(DepositCommand cmd, CancellationToken ct)
    {
        var account = await repo.GetAsync(cmd.AccountId, ct);
        account.Deposit(cmd.Amount);
        await repo.SaveAsync(account, ct);
    }
}

Register

services.AddCommandHandlersFromAssemblyContaining<DepositHandler>();

That's it — the handler is now resolved per-scope and dispatched whenever mediator.HandleAsync(new DepositCommand(...)) is called.

Mandatory hygiene

Max 7 constructor parameters (this counts as one). If you need more, group them in a sealed record parameter object.
No magic numbers — name your constants.
No manual retry loops — pull a Polly pipeline from Stratara.Resilience via IResiliencePipelineProvider<string>.
No Stopwatch — use ActivitySource.StartActivity() for timing.

Logging

Source-generated only for new code. Per-package extension class under Diagnostics/Extensions/Logger*Extensions.cs:

public static partial class LoggerAccountExtensions
{
    [LoggerMessage(
        EventId = LogEvents.MyApp.DepositApplied,
        Level = LogLevel.Information,
        Message = "Deposited {Amount} into account {AccountId}.")]
    public static partial void LogDepositApplied(this ILogger logger, decimal amount, Guid accountId);
}

Then in the handler:

logger.LogDepositApplied(cmd.Amount, cmd.AccountId);