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Editorial Team
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Asked: 2026-06-12T14:06:09+00:00

My team works with the COM API of a large simulation application. Most simulation

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My team works with the COM API of a large simulation application. Most simulation files run into the hundreds of megabytes and appear to get fully loaded into memory when they are opened.

The main task that we perform is iterating through all of the elements in the object model of the file and then doing ‘something’ to each element.

We have recently moved our code base from .NET 2 in to .NET 4 in VS 2010 and have seen the iteration speed drop by about 40 times (from ~10 seconds to about 8 minutes). We have reduced this to the smallest possible example of code (10 lines or so); compiled this in VS 2005, run it and then opened the project in VS 2010 and compiled, leaving the framework as 2 (we are using the manufacturer supplied COM interop assemblies).

In 2005 the test app completes in 10 seconds in 2010 it takes 8 minutes.

What could be causing this?

UPDATE

The code is equivalent to:

var server = new Server();
var elements = server.Elements;
var elementCount = elements.Count;

for(int i = 0; i < elementsCount; ++i)
{
    var element = elements[i];
}

This code takes 40 times longer to run through VS 2010 than VS 2005.

UPDATE 2

I rationalised that the only reason that the operation can be dramatically slower in one case than the other is that data is transferred differently over COM in the different versions.

We recorded the binding logs for both cases and this is what we found; in the fast version the native image of CustomMarshalers is not found (these are the binding logs captured by FUSLOGVW)

mscorlib

mscorlib, Version=2.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089.HTM

Fast

LOG: Start binding of native image mscorlib, Version=2.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089.
LOG: Start validating native image mscorlib, Version=2.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089.
WRN: Native image does not satisfy request. Looking for next native image.
WRN: No matching native image found.

Slow

LOG: Start binding of native image mscorlib, Version=2.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089.
LOG: Start validating native image mscorlib, Version=2.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089.
LOG: Bind to native image succeeded.

CustomMarshalers

CustomMarshalers, Version=2.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a

Fast

LOG: Start binding of native image CustomMarshalers, Version=2.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a.
LOG: Start validating native image CustomMarshalers, Version=2.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a.
WRN: Native image does not satisfy request. Looking for next native image.
WRN: No matching native image found.

Slow

LOG: Start binding of native image CustomMarshalers, Version=2.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a.
LOG: Start validating native image CustomMarshalers, Version=2.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a.
LOG: Start validating all the dependencies.
LOG: [Level 1]Start validating native image dependency mscorlib, Version=2.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089.
LOG: Dependency evaluation succeeded.
LOG: [Level 1]Start validating IL dependency Microsoft.VisualC, Version=8.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a.
LOG: Dependency evaluation succeeded.
LOG: Validation of dependencies succeeded.
LOG: Start loading all the dependencies into load context.
LOG: Loading of dependencies succeeded.
LOG: Bind to native image succeeded.
Native image has correct version information.
Attempting to use native image C:\WINDOWS\assembly\NativeImages_v2.0.50727_32\CustomMarshalers\3e6deccf191ab943d3a0812a38ab5c97\CustomMarshalers.ni.dll.
Native image successfully used.

So it looks like we get a big performance boost when the native image is not used.

Why would this bind fail in one case and succeed in an other, and how do we force the application to not use the native image?

UPDATE 3

The oddness continues. If I run this code in VS 2010 in a test method using the R# test runner, or the in-built Visual Studio test runner then it runs at the fast speed.

I have tried wrapping this code in an assembly and then loading that dynamically and that makes no difference.

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1 Answer

  1. Editorial Team

    It was kind of a long shot. Glad I could help.

    Matching MTA vs STA (threading model) is really important when making lots of distinct calls into any COM object. An [STAThread] directive at the top of a method is one way to be sure of threading model for every call in that method.

    Looks like Thread.SetApartmentState(ApartmentState.STA) will work for a whole thread, but not apparently for thread pool threads.

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