CODEWITHSUNDEEP
.netc++-cli
Ansis Māliņš
Ansis Māliņš

Reputation: 1712

#using <mscorlib.dll> in VS2012 links to 4.0 version but I need 2.0. How?

I'm trying to migrate my .NET 2.0 C++/CLI project from VS2008 to VS2012. After the conversion, the project depends on 4.0. When I do the

<TargetFrameworkVersion>v2.0</TargetFrameworkVersion>

the project depends on 2.0 and 4.0. I verify that by looking in the External Dependencies magic folder in Solution Explorer. It also gives me compiler warning when I reference the project in a 2.0 C# project.

Commenting out #includes reveals that the 4.0 dependency is pulled in by #using directives in Microsoft headers such as vcclr.h and atlbase.h.

I need these headers for the classes and functions they provide. How do I make the #using directives in them point to 2.0 version of mscorlib.dll instead of 4.0?

Upvotes: 3

Views: 4946

Answers (2)

Hans Passant
Hans Passant

Reputation: 941455

Changing the <TargetFrameworkVersion> isn't enough, the build tools still use the .NET 4 version that's installed on your machine. Something you can see by running ildasm.exe on the generated assembly. Double click the manifest to see:

// Metadata version: v4.0.30319
...
.assembly extern mscorlib
{
  .publickeytoken = (B7 7A 5C 56 19 34 E0 89 )                         // .z\V.4..
  .hash = (DD 9E C9 8D BF 2A 2D C2 AA 2D C3 8B 51 CD 4C A6   // .....*-..-..Q.L.
           15 F0 22 F6 )                                     // ..".
  .ver 2:0:0:0
}
...
.assembly extern mscorlib as mscorlib_4
{
  .publickeytoken = (B7 7A 5C 56 19 34 E0 89 )                         // .z\V.4..
  .hash = (47 6E C0 E3 BA CD CE B1 9A 4D 68 BE 29 75 61 6F   // Gn.......Mh.)uao
           BE 04 C6 BA ) 
  .ver 4:0:0:0
}

Note how both versions of mscorlib.dll ended up as a dependency. The problem you encountered.

The feedback article I linked recommended changing the toolset to "v90". This however doesn't work on my machine, even though I have VS2008 installed. The option doesn't show up in the combobox dropdown and when I force it I get this build error:

C:\Program Files (x86)\MSBuild\Microsoft.Cpp\v4.0\V110\Microsoft.Cpp.Platform.targets(43,5): error MSB8020: The builds tools for Visual Studio 2008 (Platform Toolset = 'v90') cannot be found. To build using the v90 build tools, either click the Project menu or right-click the solution, and then select "Update VC++ Projects...". Install Visual Studio 2008 to build using the Visual Studio 2008 build tools.

Following the advice given in the error message, I get this:

------ Update VC++ projects started -------
Updating project 'ConsoleApplication74'...
    Configuration 'Debug|Win32': changing Platform Toolset to 'v110' (was 'v90').
    Configuration 'Release|Win32': no update required. Platform Toolset is 'v110'.
    TargetFrameworkVersion = v4.5 (was v2.0)

Back to square one. I'd say that targeting .NET 2.0 in C++/CLI projects with VS2012 is a lost cause.

Upvotes: 4

Matt Smith
Matt Smith

Reputation: 17444

One way to do it is to open up the project file (.vcxproj) and change the

<TargetFrameworkVersion>v4.5</TargetFrameworkVersion>

to

<TargetFrameworkVersion>v2.0</TargetFrameworkVersion>

See Change C++/CLI project to another framework than 4.0 with vs2010

Upvotes: 1

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