NGEN'd assemblies not being loaded - visual-studio-2010

Question

I'm trying to measure the performance impact of NGENing my assemblies versus not but I am unable to get my executable to load the NGEN assemblies. I ran the following from the VS2010 command prompt:
ngen install MyApp.exe
This completed without any issues and I verified that all my dependency assemblies had been created in the C:\Windows\assembly\NativeImages_v4.0.30319_32\MyCompanyName# directory.
I then launched my app and looking at Process Explorer, it was loading all my assemblies from the local binaries directory instead of loading the *.ni.dll files from the NativeImages_x folder. I logged the bindings using fuslogvw. Here is a sample log entry:
*** Assembly Binder Log Entry (6/29/2011 # 10:14:04 AM) ***
The operation failed.
Bind result: hr = 0x80070002. The system cannot find the file specified.
Assembly manager loaded from: C:\Windows\Microsoft.NET\Framework64\v4.0.30319\clr.dll
Running under executable C:\Path\To\My\Binaries\MyCompanyName.MyApp.exe
--- A detailed error log follows.
=== Pre-bind state information ===
LOG: User = username
LOG: DisplayName = MyCompanyName.MyAssembly, Version=1.0.2.0, Culture=neutral, PublicKeyToken=null
(Fully-specified)
LOG: Appbase = file:///C:/Path/To/My/Binaries/
LOG: Initial PrivatePath = NULL
LOG: Dynamic Base = NULL
LOG: Cache Base = NULL
LOG: AppName = MyCompanyName.MyApp.exe
Calling assembly : MyCompanyName.AnotherAssembly, Version=1.0.2.0, Culture=neutral, PublicKeyToken=null.
===
LOG: Start binding of native image MyCompanyName.MyAssembly, Version=1.0.2.0, Culture=neutral, PublicKeyToken=null.
WRN: No matching native image found.
LOG: IL assembly loaded from C:\Path\To\My\Binaries\MyCompanyName.MyAssembly.dll
Does anyone have any thoughts on what is going on here? I verified that the native assembly in question exists at:
C:\Windows\assembly\NativeImages_v4.0.30319_32\MyCompanyName#\3a041121abf7fbdce89836c32f2d217e\MyCompanyName.MyAssembly.ni.dll
Why isn't it binding it correctly? FWIW, the application uses MEF quite a bit; I don't know if that would affect the loading of the assemblies.

Answer 1

It's because of using MEF. NGEN is only able to follow assembly references. But if you use MEF then you probably don't refer all the assemblies because MEF is responsible to load them dynamically at runtime.
Your approach is the right one. Call all assemblies with NGEN.
ngen install c:\myfiles\MyLib.dll /ExeConfig:c:\myapps\MyApp.exe
In this case you need to remove these assemblies manually from the cache when the application is uninstalled.
ngen uninstall c:\myfiles\MyLib.dll /ExeConfig:c:\myapps\MyApp.exe
See also: http://msdn.microsoft.com/en-us/library/6t9t5wcf(v=vs.100).aspx

Answer 2

I don't know what the actual issue was but the solution was to write a batch file that simply NGEN'd every binary in the directory. I guess there were binaries that were not being NGEN'd when running just the ngen install command on the top-level exe.