An item with the same key has already been added. Key: TMP

Steps to reproduce

mkdir hwapp
cd hwapp
dotnet new
dotnet restore
dotnet run

Expected behavior

I expecdted to see the “Hello World!” output.

Actual behavior

C:\Users\ohnob\OneDrive\Documents\Visual Studio 2015\Projects\hwapp>dotnet run
Project hwapp (.NETCoreApp,Version=v1.0) will be compiled because expected outputs are missing
Compiling hwapp for .NETCoreApp,Version=v1.0
An item with the same key has already been added. Key: TMP
C:\Program Files\dotnet\dotnet.exe compile-csc @C:\Users\ohnob\OneDrive\Documents\Visual Studio 2015\Projects\hwapp\obj\Debug\netcoreapp1.0\dotnet-compile.rsp returned Exit Code 1

Compilation failed.
    0 Warning(s)
    0 Error(s)

Time elapsed 00:00:00.1135244

Environment data

dotnet --info output:

C:\Users\ohnob\OneDrive\Documents\Visual Studio 2015\Projects\hwapp>dotnet --info
.NET Command Line Tools (1.0.0-preview2-003121)

Product Information:
 Version:            1.0.0-preview2-003121
 Commit SHA-1 hash:  1e9d529bc5

Runtime Environment:
 OS Name:     Windows
 OS Version:  10.0.14393
 OS Platform: Windows
 RID:         win10-x64

C:\Users\ohnob\OneDrive\Documents\Visual Studio 2015\Projects\hwapp>set | grep -ie TMP
TEMP=C:\msys64\tmp
TMP=C:\msys64\tmp
tmp=C:\Users\ohnob\AppData\Local\Temp

[inosik]

@dsplaisted you need to add two environment variables which differ in case, like FOO and foo, then run dotnet restore, or any other command, which shells out to another program. This should trigger the exception:

$ FOO=foo foo=foo dotnet restore

The problem is the new implementation of ProcessStartInfo, which behaves differently to the one in the .NET Framework. This is actually already being tracked at dotnet/corefx#13146.

[ghost]

👍 always a good idea to namespace/prefix all your environment variables with app name, e.g. DOTNETCLI_TMP.