Interop (.NET 1.1) Performance Guidelines

- J.D. Meier, Srinath Vasireddy, Ashish Babbar, and Alex Mackman

Design Considerations

• Design chunky interfaces to avoid round trips.
• Reduce round trips with a facade.
• Implement IDisposable if you hold unmanaged resources across client calls.
• Reduce or avoid the use of late binding and reflection.

Code Access Security (CAS)

• Consider using SuppressUnmanagedCode for performance-critical trusted scenarios.
• Consider using TLBIMP /unsafe for performance-critical trusted scenarios.

Marshal.ReleaseComObject

• Consider calling ReleaseComObject in server applications.
• Do not force garbage collections with GC.Collect.

Marshaling

• Explicitly name the target method you call.
• Use blittable types where possible.
• Avoid Unicode to ANSI conversions where possible.
• Use IntPtr for manual marshaling.
• Use [in] and [out] to avoid unnecessary marshaling.
• Avoid aggressive pinning of short-lived objects.

Threading

• Reduce or avoid cross-apartment calls.
• Use ASPCOMPAT when you call STA objects from ASP.NET.
• Use MTAThread when you call free-threaded objects.
• Avoid thread switches by using Neutral apartment COM components.