C# 4 and .NET 4

shared assemblies ❘ 451
Now, the assembly is in the GAC only once, but it has two references. To delete the assembly from the GAC,
both references must be removed:
gacutil /u shareddemo /r OPAQUE 4711 "Opaque installation"
gacutil /u shareddemo /r FILEPATH c:\ProCSharp\Assemblies\Client "Shared Demo"
To remove a shared assembly, the option /u requires the assembly name without the fi le
extension DLL. On the contrary, the option /i to install a shared assembly requires the
complete fi lename including the fi le extension.
Chapter 17 deals with deployment of assemblies, where the reference count is being
dealt with in an MSI package.
native image generator
With the native image generator, Ngen.exe , you can compile the IL code to native code at installation
time. This way the program can start faster because the compilation during runtime is no longer necessary.
Comparing precompiled assemblies to assemblies where the JIT compiler needs to run is not different from
a performance view after the IL code is compiled. The only improvement you get with the native image
generator is that the application starts faster because there ’ s no need to run JIT. Reducing the startup time
of the application might be enough reason for using the native image generator. In case you create a native
image from the executable, you should also create native images from all the DLLs that are loaded by
the executable. Otherwise, the JIT compiler still needs to run.
The ngen utility installs the native image in the native image cache. The physical directory of the native
image cache is < windows > \assem b l y \ N a t i v e I m a g e s .
With ngen install myassembly , you can compile the MSIL code to native code and install it into the
native image cache. This should be done from an installation program if you would like to put the assembly
in the native image cache.
With ngen , you can also display all assemblies from the native image cache with the option display . If you
add an assembly name to the display option, you get the information about all installed versions of this
assembly and the assemblies that are dependent on the native assembly:
C:\ > ngen display System.AddIn
Microsoft (R) CLR Native Image Generator - Version 4.0.21006.1
Copyright (c) Microsoft Corporation. All rights reserved.
NGEN Roots:
System.AddIn, Version=3.5.0.0, Culture=Neutral, PublicKeyToken=b77a5c561934e089,
processorArchitecture=msil
System.AddIn, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089
NGEN Roots that depend on "System.AddIn":
C:\Program Files (x86)\Common Files\Microsoft Shared\VSTA\Pipeline.v10.0\
AddInSideAdapters\Microsoft.VisualStudio.Tools.Applications.AddInAdapter.v9.0.dll
C:\Program Files (x86)\Common Files\Microsoft Shared\VSTA\Pipeline.v10.0\
AddInSideAdapters\Microsoft.VisualStudio.Tools.Office.AddInAdapter.v9.0.dll
...
If the security of the system changes, it ’ s not sure if the native image has the security requirements it needs
for running the application. This is why the native images become invalid with a system confi guration
change. With the command ngen update, all native images are rebuilt to include the new confi gurations.
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