the extern alias 'XXX' was not specified in a /reference option

Environment data

dotnet --info output:

.NET Command Line Tools (2.1.201)

Product Information:
 Version:            2.1.201
 Commit SHA-1 hash:  7932dc6179

Runtime Environment:
 OS Name:     Windows
 OS Version:  10.0.17134
 OS Platform: Windows
 RID:         win10-x64
 Base Path:   C:\Program Files\dotnet\sdk\2.1.201\

Microsoft .NET Core Shared Framework Host

  Version  : 2.0.7
  Build    : 2d61d0b043915bc948ebf98836fefe9ba942be11

VS Code version: Version 1.23.1 Commit d0182c3417d225529c6d5ad24b7572815d0de9ac Date 2018-05-10T17:11:17.614Z Shell 1.7.12 Renderer 58.0.3029.110 Node 7.9.0 Architecture x64

C# Extension version: 1.15.2

Steps to reproduce

• warning: the steps to reproduce I used visual studio to create the project. the problem comes AFTER, when i try to open the project folder within vscode:

• Create a visual studio project A.
• Add a reference to project A to any other project, B
• Go to the properties of that reference, and add an alias. something like ‘global,test’
• add a new class, and put a using statement at the top using the alias, something like extern alias test; using test::B;

Expected behavior

I expect the project to compile, or not show any compiler warnings. it works in visual studio w/out any issues

Actual behavior

i get 2 errors:

• the extern alias ‘test’ was not specified in a /reference option
• the type or namespace name ‘B’ does not exist in the namespace ‘test’

[DustinCampbell]

Thanks! I believe the issue here is that extern alias support needs to be added to the OmniSharp server (https://github.com/OmniSharp/omnisharp-rolsyn). We’ll take a look.

[filipw]

fixed in https://github.com/OmniSharp/omnisharp-roslyn/pull/1409