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

May 2004

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patterns & practices Library

How to Use This Checklist

This checklist is a companion to Chapter 7, "Improving Interop Performance"

Design Considerations

Check	Description
	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.

Marshaling

Check	Description
	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.

Marshal.ReleaseCOMObject

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

Code Access Security (CAS)

Check	Description
	Consider using SuppressUnmanagedCode for performance-critical, trusted scenarios.
	Consider using TLBIMP /unsafe for performance-critical, trusted scenarios.

Threading

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

Monitoring Interop Performance

Check	Description
	Use performance counters for P/Invoke and COM interop.
	Use CLR Spy to identify interop problems.