DISP005: Handler Should Be Sealed

Property	Value
Diagnostic ID	DISP005
Title	Handler should be sealed
Category	Excalibur.Dispatch.Messaging.Handlers
Severity	Warning
Enabled by default	Yes

Cause

A concrete handler class implements a dispatch handler interface but is not declared sealed. Sealing handler classes enables JIT devirtualization, reduces vtable overhead, and prevents accidental inheritance of framework handler types.

Examples

Non-compliant

// Warning DISP005: Handler 'CreateOrderHandler' should be declared 'sealed'
public class CreateOrderHandler : IActionHandler<CreateOrder, OrderId>
{
    public Task<OrderId> HandleAsync(CreateOrder action, CancellationToken cancellationToken)
        => Task.FromResult(new OrderId(Guid.NewGuid()));
}

Compliant

public sealed class CreateOrderHandler : IActionHandler<CreateOrder, OrderId>
{
    public Task<OrderId> HandleAsync(CreateOrder action, CancellationToken cancellationToken)
        => Task.FromResult(new OrderId(Guid.NewGuid()));
}

How to Fix

Add the sealed modifier to the handler class declaration. If the class is intentionally designed for inheritance (base handler pattern), suppress the diagnostic:

#pragma warning disable DISP005
public abstract class BaseOrderHandler : IActionHandler<CreateOrder, OrderId>
#pragma warning restore DISP005

When to Suppress

Suppress this diagnostic when:

• The handler class is an abstract base class designed for inheritance
• You have a documented pattern requiring handler polymorphism