What is the proper way to handle error CA1416 for .NET core builds?

Question

Here is my C# code snippet:

if (Environment.IsWindows) {
   _sessionAddress = GetSessionBusAddressFromSharedMemory();
}
...
[System.Runtime.Versioning.SupportedOSPlatform("windows")]
private static string GetSessionBusAddressFromSharedMemory() {
   ...
}

When I run the build, I get an error:

error CA1416: 'GetSessionBusAddressFromSharedMemory()' is supported on 'windows' 

My logic is to invoke the method only when I am on Windows. How do I turn this warning off when building on Ubuntu? Regards.

Answer 1

You can use a preprocessor directive to make sure that the method gets seen at compile time only in Windows:

#if Windows
private static string GetSessionBusAddressFromSharedMemory() 
{
   ...
}
#endif

To define the directives you need to update your csproj as follows:

<Project Sdk="Microsoft.NET.Sdk">
  <PropertyGroup>
    <OutputType>Exe</OutputType>
    <TargetFramework>netcoreapp2.0</TargetFramework>
    <IsWindows Condition="'$([System.Runtime.InteropServices.RuntimeInformation]::IsOSPlatform($([System.Runtime.InteropServices.OSPlatform]::Windows)))' == 'true'">true</IsWindows>
    <IsOSX Condition="'$([System.Runtime.InteropServices.RuntimeInformation]::IsOSPlatform($([System.Runtime.InteropServices.OSPlatform]::OSX)))' == 'true'">true</IsOSX>
    <IsLinux Condition="'$([System.Runtime.InteropServices.RuntimeInformation]::IsOSPlatform($([System.Runtime.InteropServices.OSPlatform]::Linux)))' == 'true'">true</IsLinux>
  </PropertyGroup>
  <PropertyGroup Condition="'$(IsWindows)'=='true'">
    <DefineConstants>Windows</DefineConstants>
  </PropertyGroup>
  <PropertyGroup Condition="'$(IsOSX)'=='true'">
    <DefineConstants>OSX</DefineConstants>
  </PropertyGroup>
  <PropertyGroup Condition="'$(IsLinux)'=='true'">
    <DefineConstants>Linux</DefineConstants>
  </PropertyGroup>
</Project>

Answer 2

If you have control over the Environment.IsWindows property you can apply [SupportedOSPlatformGuard("windows")] attribute to that property:

public class Environment
{
    [SupportedOSPlatformGuard("windows")]
    public bool IsWindows => OperatingSystem.IsWindows;
}

Then the CA1416 analyzer would recognize the guard and would not warn within the conditional:

if (Environment.IsWindows) {
   _sessionAddress = GetSessionBusAddressFromSharedMemory(); // no warning
}

For more info

Answer 3

You can switch to RuntimeInformation.IsOSPlatform check. Next will give warning only for last clause:

public void M()
{
    if (RuntimeInformation.IsOSPlatform(OSPlatform.Windows))
    {
        Console.WriteLine(GetSessionBusAddressFromSharedMemory());
    }
    else if (RuntimeInformation.IsOSPlatform(OSPlatform.Linux))
    {
        Console.WriteLine(GetSessionBusAddressFromSharedMemoryUnix());
    }
    else
    {
        Console.WriteLine(GetSessionBusAddressFromSharedMemoryUnix()); // warning
    }
}

[SupportedOSPlatform("windows")]
private static string GetSessionBusAddressFromSharedMemory()
{
    return "win";
}

[SupportedOSPlatform("linux")]
private static string GetSessionBusAddressFromSharedMemoryUnix()
{
    return "lin";
}