perf: use VLB and make methods sync in EventReceiverOrchestrator

[TimothyMakkison]

• Make methods synchronous
• Use ValueListBuilder in RegisterReceivers

Before

After

Fun fact: Attribute.Equals and Attribute.GetHashCode allocate a FieldInfo[] each time they are called.

[thomhurst]

Summary

Performance optimization using ValueListBuilder for allocation reduction and making methods synchronous.

Critical Issues

Missing try-finally in RegisterReceivers (line 41-77): The ValueListBuilder is only disposed if no exception occurs. This could leak array pool buffers.

Verdict

REQUEST CHANGES - Need try-finally block around VLB usage.

[thomhurst]

Detailed Fix

In EventReceiverOrchestrator.RegisterReceivers, the ValueListBuilder needs try-finally:

Before: vlb.Dispose() only runs if no exception occurs
After: Wrap the usage in try-finally to guarantee disposal

This prevents leaking array pool buffers when exceptions occur during event object enumeration or registration.

Performance Notes

The changes are excellent for performance:

• ValueListBuilder reduces allocations vs List
• Synchronous methods avoid async state machine overhead
• Early exit checks prevent allocations when no receivers exist

The only minor point is the duplicated early-exit logic in InvokeTestEndEventReceiversAsync, but the performance benefit likely justifies it.