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.NET assemblies

In this recipe:

Troubleshooting loading using ETW (in Perfview)

I think that currently the most efficient way to diagnose problems with assembly loading is to collect ETW events from the .NET ETW provider. There is a bunch of them under the Microsoft-Windows-DotNETRuntimePrivate/Binding/ category.

For this purpose you may use the PerfView util. Just make sure that you have the .NET check box selected in the collection dialog (it should be by default). Start collection and stop it after the loading exception occurs. Then open the .etl file, go to the Events screen and filter them by binding as you can see on the screenshot below:

events

Select all of the events and press ENTER. PerfView will immediately print the instances of the selected events in the grid on the right. You may later search or filter the grid with the help of the search boxes above it.

Troubleshooting loading using Fusion Log

Fusion log is available in all versions of .NET Framework. There is a tool named fuslogvw which you may use to set the fusion log configuration but this tool might not be available on a server. In such a case just apply the registry settings described below.

The root of all the Fusion log settings is HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Fusion.

It is possible to log bindings also of the native images - you need to select the Native Images checkbox.

When writing to a folder on a hard drive fusion logs are split among categories and processes, eg.:

C:\TEMP\FUSLOGVW
├───Default
│   └───powershell.exe
└───NativeImage
    └───powershell.exe

Log to exception text

HKEY_LOCAL_MACHINE\software\microsoft\fusion
    EnableLog    REG_DWORD    0x1

Command:

reg delete HKLM\Software\Microsoft\Fusion /va
reg add HKLM\Software\Microsoft\Fusion /v EnableLog /t REG_DWORD /d 0x1

Log failures to disk

HKEY_LOCAL_MACHINE\software\microsoft\fusion
    LogFailures    REG_DWORD    0x1
    LogPath    REG_SZ    c:\logs\fuslogvw

Command:

reg delete HKLM\Software\Microsoft\Fusion /va
reg add HKLM\Software\Microsoft\Fusion /v LogFailures /t REG_DWORD /d 0x1
reg add HKLM\Software\Microsoft\Fusion /v LogPath /t REG_SZ /d "C:\logs\fuslogvw"

Log all binds to disk

HKEY_LOCAL_MACHINE\software\microsoft\fusion
    LogPath    REG_SZ    c:\logs\fuslogvw
    ForceLog    REG_DWORD    0x1

Command:

reg delete HKLM\Software\Microsoft\Fusion /va
reg add HKLM\Software\Microsoft\Fusion /v ForceLog /t REG_DWORD /d 0x1
reg add HKLM\Software\Microsoft\Fusion /v LogPath /t REG_SZ /d "C:\logs\fuslogvw"

Log disabled

HKEY_LOCAL_MACHINE\software\microsoft\fusion
    LogPath    REG_SZ    c:\logs\fuslogvw

Command:

reg delete HKLM\Software\Microsoft\Fusion /va

Decompile, view metadata (ildasm.exe)

ildasm /OUT:

Prints the disassembled information into the provided file.

ildasm /METADATA[=]

Gathers metadata defined in the assembly. Possible specifiers:

  • MDHEADER Show MetaData header information and sizes.
  • HEX Show more things in hex as well as words.
  • CSV Show the record counts and heap sizes.
  • UNREX Show unresolved externals.
  • SCHEMA Show the MetaData header and schema information.
  • RAW Show the raw MetaData tables.
  • HEAPS Show the raw heaps.
  • VALIDATE Validate the consistency of the metadata.

Example output:

// ===========================================================
// ScopeName : ConsoleApplication1.exe
// MVID      : {46761126-7A8E-40AC-ADD8-7D0AFD43D268}
// ===========================================================
// Global functions
// -------------------------------------------------------
//
// Global fields
// -------------------------------------------------------
//
// Global MemberRefs
// -------------------------------------------------------
//
// TypeDef #1 (02000002)
// -------------------------------------------------------
// 	TypDefName: ConsoleApplication1.Program  (02000002)
// 	Flags     : [NotPublic] [AutoLayout] [Class] [AnsiClass] [BeforeFieldInit]  (00100000)
// 	Extends   : 01000001 [TypeRef] System.Object
// 	Method #1 (06000001)
// 	-------------------------------------------------------
// 		MethodName: Test (06000001)
// 		Flags     : [Private] [Static] [HideBySig] [ReuseSlot]  (00000091)
// 		RVA       : 0x00002050
// 		ImplFlags : [IL] [Managed]  (00000000)
// 		CallCnvntn: [DEFAULT]
// 		ReturnType: Void
// 		No arguments.
//
// 	Method #2 (06000002) [ENTRYPOINT]
// 	-------------------------------------------------------
// 		MethodName: Main (06000002)
// 		Flags     : [Private] [Static] [HideBySig] [ReuseSlot]  (00000091)
// 		RVA       : 0x00002098
// 		ImplFlags : [IL] [Managed]  (00000000)
// 		CallCnvntn: [DEFAULT]
// 		ReturnType: Void
// 		1 Arguments
// 			Argument #1:  SZArray String
// 		1 Parameters
// 			(1) ParamToken : (08000001) Name : args flags: [none] (00000000)

Working with assembly signaures (sn.exe)

Display public key of an assembly (sn.exe -Tp)

Display/check token for public key of (-Tp)

c:>sn -Tp Trader.Core.dll

Microsoft (R) .NET Framework Strong Name Utility  Version 4.0.30319.1
Copyright (c) Microsoft Corporation.  All rights reserved.

Public key is
0024000004800000940000000602000000240000525341310004000001000100316e8953d38cfd
180738ed096f1dffa5534335936caab5fee6702f750031c72a87f2e24d184b8282eee5eab3d2ed
74c7c9acc11638fcd6534d6fd5eaf56e8ce690dbcf1d51b714f7a55d6f17b40fa621e7cb7ba5f4
e7f283e5793fd24fa2286f691a40fc8a373e6b2bb24f77b52890f2fe698a9afb35640cbd0a7541
dcd669d6

Public key token is d687cd68612aadaa

Examine/modify assemblies bitness (corflags.exe)

Remove the 32BIT flag:

C:>corflags Program.exe
Microsoft (R) .NET Framework CorFlags Conversion Tool.  Version  4.0.30319.1
Copyright (c) Microsoft Corporation.  All rights reserved.

Version   : v2.0.50727
CLR Header: 2.5
PE        : PE32
CorFlags  : 3
ILONLY    : 1
32BIT     : 1
Signed    : 0

C:>corflags /32bit- Program.exe
Microsoft (R) .NET Framework CorFlags Conversion Tool.  Version  4.0.30319.1
Copyright (c) Microsoft Corporation.  All rights reserved.

C:>corflags Program.exe
Microsoft (R) .NET Framework CorFlags Conversion Tool.  Version  4.0.30319.1
Copyright (c) Microsoft Corporation.  All rights reserved.

Version   : v2.0.50727
CLR Header: 2.5
PE        : PE32
CorFlags  : 1
ILONLY    : 1
32BIT     : 0
Signed    : 0

GAC

For .NET2.0/3.5 gac was located in c:\Windows\assembly folder with a drag/drop option for installing/uninstalling assemblies. According to http://stackoverflow.com/questions/10013047/gacutil-vs-manually-editing-c-windows-assembly:

This functionality is provided by a custom shell extension, shfusion.dll. It flattens the GAC and makes it look like a single folder. And takes care of automatically un/registering the assemblies for you when you manipulate the explorer window. So you’re fine doing this.

Note that this will no longer work for .NET 4, it uses a GAC in a different folder (c:\windows\microsoft.net\assembly) and that folder does not have a the same kind of shell extension, you see the raw content of the GAC folders. Don’t mess with that one.

For .NET4.0 GAC was moved to c:\Windows\Microsoft.NET\assembly and no longer supports drag&drop functionality - so it’s best to just use gacutil to manipulate GAC content. To disable GAC viewer in Windows Explorer, add a DWORD value DisableCacheViewer set to 1 under the HKLM\Software\Microsoft\Fusion key. Though it’s possible to install assembly in both GAC folders as stated here: http://stackoverflow.com/questions/7095887/registering-the-same-version-of-an-assembly-but-with-different-target-frameworks, but I would not consider it a good practice as framework tools can’t deal with it.

.NET GAC settings are stored under the registry key: HKLM\Software\Microsoft\Fusion.

Find assembly in cache

Work only with full assembly name provided. If no name is provided lists all the assemblies in cache.

gacutil /l System.Core

The Global Assembly Cache contains the following assemblies:
  System.Core, Version=3.5.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089, processorArchitecture=MSIL
  System.Core, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089, processorArchitecture=MSIL

Number of items = 2

Uninstall assembly from cache

gacutil /u MyTest.exe

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