Default font family name can't be null or empty

[NyasakiAT]

[mwalk@arch netcoreapp3.1]$ ./AvalonStudio
Unhandled exception. System.InvalidOperationException: Default font family name can't be null or empty.
at Avalonia.Media.FontManager..ctor(IFontManagerImpl platformImpl)
at Avalonia.Media.FontManager.get_Current()
at Avalonia.Rendering.RendererBase..ctor(Boolean useManualFpsCounting)
at Avalonia.Rendering.DeferredRenderer..ctor(IRenderRoot root, IRenderLoop renderLoop, ISceneBuilder sceneBuilder, IDispatcher dispatcher, IDeferredRendererLock rendererLock)
at Avalonia.X11.X11Window.CreateRenderer(IRenderRoot root)
at Avalonia.Controls.TopLevel..ctor(ITopLevelImpl impl, IAvaloniaDependencyResolver dependencyResolver)
at Avalonia.Controls.WindowBase..ctor(IWindowBaseImpl impl, IAvaloniaDependencyResolver dependencyResolver)
at Avalonia.Controls.WindowBase..ctor(IWindowBaseImpl impl)
at Avalonia.Controls.Window..ctor(IWindowImpl impl)
at Avalonia.Controls.Window..ctor()
at AvalonStudio.Shell.Controls.MetroWindow..ctor() in /home/mwalk/tmp/AvalonStudio/AvalonStudio.Shell/src/AvalonStudio.Shell/Controls/MetroWindow.cs:line 63
at AvalonStudio.MainWindow..ctor() in /home/mwalk/tmp/AvalonStudio/AvalonStudio/AvalonStudio/MainWindow.xaml.cs:line 15
at AvalonStudio.App.OnFrameworkInitializationCompleted() in /home/mwalk/tmp/AvalonStudio/AvalonStudio/AvalonStudio/App.paml.cs:line 18
at Avalonia.Controls.AppBuilderBase1.Setup() at Avalonia.Controls.AppBuilderBase1.SetupWithLifetime(IApplicationLifetime lifetime)
at Avalonia.ClassicDesktopStyleApplicationLifetimeExtensions.StartWithClassicDesktopLifetime[T](T builder, String[] args, ShutdownMode shutdownMode)
at AvalonStudio.Shell.Shell.StartShellApp[TAppBuilder](TAppBuilder builder, String appName, ShellAppMainDelegate main, String[] args, IFactory layoutFactory) in /home/mwalk/tmp/AvalonStudio/AvalonStudio.Shell/src/AvalonStudio.Shell/Shell.cs:line 17
at AvalonStudio.Program.Main(String[] args) in /home/mwalk/tmp/AvalonStudio/AvalonStudio/AvalonStudio/Program.cs:line 32
Aborted (core dumped)
[mwalk@arch netcoreapp3.1]$ ./AvalonStudio
Unhandled exception. System.InvalidOperationException: Default font family name can't be null or empty.
at Avalonia.Media.FontManager..ctor(IFontManagerImpl platformImpl)
at Avalonia.Media.FontManager.get_Current()
at Avalonia.Rendering.RendererBase..ctor(Boolean useManualFpsCounting)
at Avalonia.Rendering.DeferredRenderer..ctor(IRenderRoot root, IRenderLoop renderLoop, ISceneBuilder sceneBuilder, IDispatcher dispatcher, IDeferredRendererLock rendererLock)
at Avalonia.X11.X11Window.CreateRenderer(IRenderRoot root)
at Avalonia.Controls.TopLevel..ctor(ITopLevelImpl impl, IAvaloniaDependencyResolver dependencyResolver)
at Avalonia.Controls.WindowBase..ctor(IWindowBaseImpl impl, IAvaloniaDependencyResolver dependencyResolver)
at Avalonia.Controls.WindowBase..ctor(IWindowBaseImpl impl)
at Avalonia.Controls.Window..ctor(IWindowImpl impl)
at Avalonia.Controls.Window..ctor()
at AvalonStudio.Shell.Controls.MetroWindow..ctor() in /home/mwalk/tmp/AvalonStudio/AvalonStudio.Shell/src/AvalonStudio.Shell/Controls/MetroWindow.cs:line 63
at AvalonStudio.MainWindow..ctor() in /home/mwalk/tmp/AvalonStudio/AvalonStudio/AvalonStudio/MainWindow.xaml.cs:line 15
at AvalonStudio.App.OnFrameworkInitializationCompleted() in /home/mwalk/tmp/AvalonStudio/AvalonStudio/AvalonStudio/App.paml.cs:line 18
at Avalonia.Controls.AppBuilderBase1.Setup() at Avalonia.Controls.AppBuilderBase1.SetupWithLifetime(IApplicationLifetime lifetime)
at Avalonia.ClassicDesktopStyleApplicationLifetimeExtensions.StartWithClassicDesktopLifetime[T](T builder, String[] args, ShutdownMode shutdownMode)
at AvalonStudio.Shell.Shell.StartShellApp[TAppBuilder](TAppBuilder builder, String appName, ShellAppMainDelegate main, String[] args, IFactory layoutFactory) in /home/mwalk/tmp/AvalonStudio/AvalonStudio.Shell/src/AvalonStudio.Shell/Shell.cs:line 17
at AvalonStudio.Program.Main(String[] args) in /home/mwalk/tmp/AvalonStudio/AvalonStudio/AvalonStudio/Program.cs:line 32
Aborted (core dumped)

Project was build normally and I attempted to run it
Fresh Archlinux install with i3

[viko-stamoff]

I have the same problem here. Fonts are installed, but still gives a error

OS: Manjaro Linux (fully updated as of 11th Sep 2020)
Dotnet Version 3.1.107
Error Message:

Unhandled exception. System.InvalidOperationException: Default font family name can't be null or empty.
at Avalonia.Media.FontManager..ctor(IFontManagerImpl platformImpl)
at Avalonia.Media.FontManager.get_Current()
at Avalonia.Rendering.RendererBase..ctor(Boolean useManualFpsCounting)
at Avalonia.Rendering.DeferredRenderer..ctor(IRenderRoot root, IRenderLoop renderLoop, ISceneBuilder sceneBuilder, IDispatcher dispatcher, IDeferredRendererLock rendererLock)
at Avalonia.X11.X11Window.CreateRenderer(IRenderRoot root)
at Avalonia.Controls.TopLevel..ctor(ITopLevelImpl impl, IAvaloniaDependencyResolver dependencyResolver)
at Avalonia.Controls.WindowBase..ctor(IWindowBaseImpl impl, IAvaloniaDependencyResolver dependencyResolver)
at Avalonia.Controls.WindowBase..ctor(IWindowBaseImpl impl)
at Avalonia.Controls.Window..ctor(IWindowImpl impl)
at Avalonia.Controls.Window..ctor()
at AvalonStudio.Shell.Controls.MetroWindow..ctor() in /opt/AvalonStudio/AvalonStudio.Shell/src/AvalonStudio.Shell/Controls/MetroWindow.cs:line 63
at AvalonStudio.MainWindow..ctor() in /opt/AvalonStudio/AvalonStudio/AvalonStudio/MainWindow.xaml.cs:line 15
at AvalonStudio.App.OnFrameworkInitializationCompleted() in /opt/AvalonStudio/AvalonStudio/AvalonStudio/App.paml.cs:line 18
at Avalonia.Controls.AppBuilderBase1.Setup() at Avalonia.Controls.AppBuilderBase1.SetupWithLifetime(IApplicationLifetime lifetime)
at Avalonia.ClassicDesktopStyleApplicationLifetimeExtensions.StartWithClassicDesktopLifetime[T](T builder, String[] args, ShutdownMode shutdownMode)
at AvalonStudio.Shell.Shell.StartShellApp[TAppBuilder](TAppBuilder builder, String appName, ShellAppMainDelegate main, String[] args, IFactory layoutFactory) in /opt/AvalonStudio/AvalonStudio.Shell/src/AvalonStudio.Shell/Shell.cs:line 17
at AvalonStudio.Program.Main(String[] args) in /opt/AvalonStudio/AvalonStudio/AvalonStudio/Program.cs:line 32
zsh: abort (core dumped) ./AvalonStudio

[ErdajtSopjani]

Same issue here in Arch Linux:

❯ dotnet run
/home/erdajtt/P9/code/c#/projects/test/ViewLocator.cs(12,20): warning CS8602: Dereference of a possibly null reference. [/home/erdajtt/P9/code/c#/projects/test/test.csproj]
Unhandled exception. System.InvalidOperationException: Default font family name can't be null or empty.
   at Avalonia.Media.FontManager..ctor(IFontManagerImpl platformImpl)
   at Avalonia.Media.FontManager.get_Current()
   at Avalonia.AppBuilder.<>c__DisplayClass62_0.<ConfigureFonts>b__0(AppBuilder appBuilder)
   at Avalonia.AppBuilder.SetupUnsafe()
   at Avalonia.AppBuilder.Setup()
   at Avalonia.AppBuilder.SetupWithLifetime(IApplicationLifetime lifetime)
   at Avalonia.ClassicDesktopStyleApplicationLifetimeExtensions.StartWithClassicDesktopLifetime(AppBuilder builder, String[] args, ShutdownMode shutdownMode)
   at test.Program.Main(String[] args) in /home/erdajtt/P9/code/c#/projects/test/Program.cs:line 13

[ErdajtSopjani]

To resolve this issue install ttf-ms-fonts from the AUR. (in arch based distros)

yay -S ttf-ms-fonts

And for ubuntu based distros install ttf-mscorefonts-installer from the repos.