dotnet/msbuild

MSB3243 warning is issued when project references two assemblies with same simple name, but with different strong names.

Open

#715 opened on Jun 21, 2016

View on GitHub
 (7 comments) (4 reactions) (0 assignees)C# (5,062 stars) (1,364 forks)batch import
backloghelp wantedtriaged

Description

If you have a project referencing two assemblies with different strong names, but same simple name:

Library, Version=2.0.0.0, Culture=neutral, PublicKeyToken=63dc4c2e4fb85cbb
Library, Version=1.0.0.0, Culture=neutral, PublicKeyToken=282ebfd59330c047

...MSBuild issues bogus warning MSB3243:

3>  There was a conflict between "Library, Version=2.0.0.0, Culture=neutral, PublicKeyToken=63dc4c2e4fb85cbb" and "Library, Version=1.0.0.0, Culture=neutral, PublicKeyToken=282ebfd59330c047".
3>C:\Program Files (x86)\MSBuild\15.0\bin\Microsoft.Common.CurrentVersion.targets(1820,5): warning MSB3243: No way to resolve conflict between "Library, Version=2.0.0.0, Culture=neutral, PublicKeyToken=63dc4c2e4fb85cbb" and "Library, Version=1.0.0.0, Culture=neutral, PublicKeyToken=282ebfd59330c047". Choosing "Library, Version=2.0.0.0, Culture=neutral, PublicKeyToken=63dc4c2e4fb85cbb" arbitrarily.

In reality, both assemblies are given different aliases in project file:

    <ProjectReference Include="..\Library1\Library1.csproj">
      <Project>{5effb800-ff22-4fdd-a0b0-bdc04cd2862e}</Project>
      <Name>Library1</Name>
      <Aliases>Library1</Aliases>
    </ProjectReference>
    <ProjectReference Include="..\Library2\Library2.csproj">
      <Project>{1a61b570-2451-4632-94fe-4a467e7c339c}</Project>
      <Name>Library2</Name>
      <Aliases>Library2</Aliases>
    </ProjectReference>

...and code uses extern alias directives to distinguish them:

extern alias Library1;
extern alias Library2;

Take repro solution compile it, and add both Library.dll's to the GAC. Repro.exe works just fine.

Contributor guide

Tech stack
csharp
Domain
build systemdeveloper experience
Issue type
bug
DifficultyEstimated implementation difficulty for a new contributor, from 1 for very small changes to 5 for expert-level work.
3
Estimated timeA rough time range for an experienced contributor to investigate, implement, test, and prepare a pull request.
1-3 hours
Activity statusHow available the issue appears right now: fresh, active, stale, blocked, or waiting on maintainer input.
stale
ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.
clear
Prerequisites
C#MSBuildstrong naming
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
30
Research direction
This is a bug in MSBuild's assembly resolution conflict detection when two assemblies share the same simple name but differ in strong name, and are used with extern alias directives. The warning is emitted in Microsoft.Common.CurrentVersion.targets around line 1820. A fix should modify the conflict resolution logic to correctly handle assemblies that are disambiguated via aliases. The provided repro project should be built and both libraries added to the GAC. Reviewing comments may reveal additional insights or partial fixes.