HintPath vs ReferencePath in Visual Studio

According to this MSDN blog: https://blogs.msdn.microsoft.com/manishagarwal/2005/09/28/resolving-file-references-in-team-build-part-2/

There is a search order for assemblies when building. The search order is as follows:

Files from the current project – indicated by ${CandidateAssemblyFiles}.
$(ReferencePath) property that comes from .user/targets file.
%(HintPath) metadata indicated by reference item.
Target framework directory.
Directories found in registry that uses AssemblyFoldersEx Registration.
Registered assembly folders, indicated by ${AssemblyFolders}.
$(OutputPath) or $(OutDir)
GAC

So, if the desired assembly is found by HintPath, but an alternate assembly can be found using ReferencePath, it will prefer the ReferencePath'd assembly to the HintPath'd one.

Look in the file Microsoft.Common.targets

The answer to the question is in the file Microsoft.Common.targets for your target framework version.

For .Net Framework version 4.0 (and 4.5 !) the AssemblySearchPaths-element is defined like this:

    <!--
    The SearchPaths property is set to find assemblies in the following order:

        (1) Files from current project - indicated by {CandidateAssemblyFiles}
        (2) $(ReferencePath) - the reference path property, which comes from the .USER file.
        (3) The hintpath from the referenced item itself, indicated by {HintPathFromItem}.
        (4) The directory of MSBuild's "target" runtime from GetFrameworkPath.
            The "target" runtime folder is the folder of the runtime that MSBuild is a part of.
        (5) Registered assembly folders, indicated by {Registry:*,*,*}
        (6) Legacy registered assembly folders, indicated by {AssemblyFolders}
        (7) Resolve to the GAC.
        (8) Treat the reference's Include as if it were a real file name.
        (9) Look in the application's output folder (like bin\debug)
    -->
<AssemblySearchPaths Condition=" '$(AssemblySearchPaths)' == ''">
  {CandidateAssemblyFiles};
  $(ReferencePath);
  {HintPathFromItem};
  {TargetFrameworkDirectory};
  {Registry:$(FrameworkRegistryBase),$(TargetFrameworkVersion),$(AssemblyFoldersSuffix)$(AssemblyFoldersExConditions)};
  {AssemblyFolders};
  {GAC};
  {RawFileName};
  $(OutDir)
</AssemblySearchPaths>

For .Net Framework 3.5 the definition is the same, but the comment is wrong. The 2.0 definition is slightly different, it uses $(OutputPath) instead of $(OutDir).

On my machine I have the following versions of the file Microsoft.Common.targets:

C:\Windows\Microsoft.NET\Framework\v2.0.50727\Microsoft.Common.targets
C:\Windows\Microsoft.NET\Framework\v3.5\Microsoft.Common.targets
C:\Windows\Microsoft.NET\Framework\v4.0.30319\Microsoft.Common.targets

C:\Windows\Microsoft.NET\Framework64\v2.0.50727\Microsoft.Common.targets
C:\Windows\Microsoft.NET\Framework64\v3.5\Microsoft.Common.targets
C:\Windows\Microsoft.NET\Framework64\v4.0.30319\Microsoft.Common.targets

This is with Visual Studio 2008, 2010 and 2013 installed on Windows 7.

The fact that the output directory is searched can be a bit frustrating (as the original poster points out) because it may hide an incorrect HintPath. The solution builds OK on your local machine, but breaks when you build on in a clean folder structure (e.g. on the build machine).

My own experience has been that it's best to stick to one of two kinds of assembly references:

A 'local' assembly in the current build directory
An assembly in the GAC

I've found (much like you've described) other methods to either be too easily broken or have annoying maintenance requirements.

Any assembly I don't want to GAC, has to live in the execution directory. Any assembly that isn't or can't be in the execution directory I GAC (managed by automatic build events).

This hasn't given me any problems so far. While I'm sure there's a situation where it won't work, the usual answer to any problem has been "oh, just GAC it!". 8 D

Hope that helps!

Although this is an old document, but it helped me resolve the problem of 'HintPath' being ignored on another machine. It was because the referenced DLL needed to be in source control as well:

https://msdn.microsoft.com/en-us/library/ee817675.aspx#tdlg_ch4_includeoutersystemassemblieswithprojects

Excerpt:

To include and then reference an outer-system assembly
1. In Solution Explorer, right-click the project that needs to reference the assembly,,and then click Add Existing Item.
2. Browse to the assembly, and then click OK. The assembly is then copied into the project folder and automatically added to VSS (assuming the project is already under source control).
3. Use the Browse button in the Add Reference dialog box to set a file reference to assembly in the project folder.

HintPath vs ReferencePath in Visual Studio

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