How do you pass conditional compilation symbols (DefineConstants) to msbuild

Question

So, both this and this are pretty clear. Simply pass `/p:DefineConstants="SYMBOL"` It doesn't work at all for me, even in a test project. I'm expecting that passing /p:DefineConstants="SYMBOL" will override any conditional compilation constants defined in the csproj. Not the case however... Full code listing below: ``` using System; using System.Collections.Generic; using System.Linq; using System.Text; namespace DefineConstants { class Program { static void Main(string[] args) { #if DEV Console.WriteLine("DEV"); #elif UAT Console.WriteLine("UAT"); #else Console.WriteLine("No environment provided"); #endif } } } ``` .csproj file is: ``` Debug x86 8.0.30703

Accepted Answer

Using `DefineConstants` definitely does work. Which means you are doing something wrong. My guess is you first built the project without defining anything, then built it again. MSBuild will then see the project was built already and won't build again, but just copy output files. You should post the output of msbuild so we can be sure, but for reference I compiled your project using the necessary switches only and here is the result (full msbuild output omitted):

```
> msbuild ConsoleApplication1.sln /p:DefineConstants="DEV" /t:Rebuild
....
Building solution configuration "Debug|x86".
Project ... is building ConsoleApplication1.csproj" (Rebuild target(s)).
...
> ConsoleApplication1\bin\Debug\DefineConstants.exe
DEV
> msbuild ConsoleApplication1.sln /p:DefineConstants="UAT" /t:Rebuild
...
> ConsoleApplication1\bin\Debug\DefineConstants.exe
UAT
> msbuild ConsoleApplication1.sln /t:Rebuild
...
> ConsoleApplication1\bin\Debug\DefineConstants.exe
No environment provided 
```

How do you pass conditional compilation symbols (DefineConstants) to msbuild

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