aelij/RoslynDeterministic.md

## RoslynDeterministic.md

      
        

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              RoslynDeterministic.md
            
          
        
      
    
  
    Deterministic Builds in C#
Status
The C# compiler (Roslyn) supports deterministic builds since Visual Studio 2015.
This means that compiling assemblies under the same conditions (permalink) would produce byte-for-byte equivalent binaries.
If you also intend on shipping non-portable (permalink)) PDBs, you must also make sure that paths in the PDBs are absolute using path mapping. The recommended way would be to map the enlistment (repo) root to a fixed path, such as C:\.
For more information, see this blog post.
How To

Deterministic requires Visual Studio 2015 (Roslyn version 1.0).
PathMap requires Visual Studio 2015 Update 3 (Roslyn version 1.3).

In MSBuild (.csproj) - assuming you've defined the property EnlistmentRoot somewhere:
<Project>
  <PropertyGroup>
    <Deterministic>true</Deterministic>
    <PathMap>$(EnlistmentRoot)=C:\</Features>
  </PropertyGroup>
</Project>
In the compiler command-line:
> csc /deterministic /pathmap:C:\Source\MyRepo=C:\