Can't seem to use #if in Cross-Platform Library

[stefanolson]

Current behavior

Error CS0234: The type or namespace name 'Data' does not exist in the namespace 'System.Windows' (are you missing an assembly reference?)

When using #if to share code with a WPF project in a Cross-Platform Library. System.Windows is WPF code that the compiler should be ignoring

Expected behavior

Compile with no issues.

How to reproduce it (as minimally and precisely as possible)

Create a new uno project. Within the project create a new 'Cross-Platform Library'. In the class library class, insert the following code:
`using System;
#if UNO_1213
using Windows.UI.Xaml.Data;
#else
using System.Windows.Data;
using System.Windows;
#endif

namespace ClassLibrary
{
public class Class1:IValueConverter
{
public object Convert(object value, Type targetType, object parameter, string language)
{
throw new NotImplementedException();
}

public object ConvertBack(object value, Type targetType, object parameter, string language)
{
    throw new NotImplementedException();
}

}
}

In the Properties for the class library project define a conditional symbol of UNO_1213. Visual Studio doesn't seem to know that UNO_1213 is defined because IValueConverter remains red - yet Windows.UI.Xaml.Data is not grayed out. So it obviously understands it's turned on to some extent. If I change the #if to something else it does become grayed out:

Sample project including msbuild.binlog enclosed

Workaround

None so far

Environment

Nuget Package:

• Uno.UI / Uno.UI.WebAssembly / Uno.UI.Skia
• Uno.WinUI / Uno.WinUI.WebAssembly / Uno.WinUI.Skia
• Uno.SourceGenerationTasks
• Uno.UI.RemoteControl / Uno.WinUI.RemoteControl
• Other:

Nuget Package Version(s):

Affected platform(s):

• iOS
• Android
• WebAssembly
• WebAssembly renderers for Xamarin.Forms
• macOS
• Skia
  • WPF
  • GTK (Linux)
• Windows
• Build tasks
• Solution Templates

IDE:

• Visual Studio 2017 (version: )
• Visual Studio 2019 (version: 16.7.2)
• Visual Studio for Mac (version: )
• Rider Windows (version: )
• Rider macOS (version: )
• Visual Studio Code (version: )

Relevant plugins:

• Resharper (version: )

UnoTester.zip

[davidjohnoliver]

Thanks for the report!

Looking at the .csproj file in your repro, this is arising because the conditional symbol is only defined for the UWP target:

  <PropertyGroup Condition="'$(Configuration)|$(TargetFramework)|$(Platform)'=='Release|uap10.0.18362|AnyCPU'">
    <DefineConstants>UNO_1213</DefineConstants>
  </PropertyGroup>
  <PropertyGroup Condition="'$(Configuration)|$(TargetFramework)|$(Platform)'=='Debug|uap10.0.18362|AnyCPU'">
    <DefineConstants>UNO_1213</DefineConstants>
  </PropertyGroup>

therefore it's failing to build for the other targets.

If you replace the above in ClassLibrary.csproj with

  <PropertyGroup>
    <DefineConstants>UNO_1213</DefineConstants>
  </PropertyGroup>

all targets should build successfully.

[stefanolson]

Thanks! Build now works. Hopefully visual studio will improve their tooling to keep up with the capabilities of the uno platform!

[jeromelaban]

Indeed. The fact that .NET 5 will be more on the cross-targeting side that previously will help a lot for that.