Fix

src/Web/Avalonia.Web.Sample/Program.cs

@@ -30,7 +30,8 @@ internal partial class Program
         var canvas = AvaloniaRuntime.CreateCanvas(div);
 
         Console.WriteLine("Created canvas");
-        
+
+        AvaloniaRuntime.Foo(canvas);
     }
 }
 

src/Web/Avalonia.Web.Sample/main.js

@@ -2,6 +2,7 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 
 import { dotnet } from './dotnet.js'
+import { createAvaloniaRuntime } from './avalonia.js';
 
 const is_browser = typeof window != "undefined";
 if (!is_browser) throw new Error(`Expected to be running in a browser`);
@@ -11,6 +12,8 @@ const dotnetRuntime = await dotnet
     .withApplicationArgumentsFromQuery()
     .create();
 
+await createAvaloniaRuntime(dotnetRuntime);
+
 const config = dotnetRuntime.getConfig();
 
 await dotnetRuntime.runMainAndExit(config.mainAssemblyName, ["dotnet", "is", "great!"]);

src/Web/Avalonia.Web/AvaloniaRuntime.cs

@@ -29,11 +29,11 @@ public partial class AvaloniaRuntime
         Console.WriteLine($"{glInfo.ContextId}, {glInfo.FboId}");
     }
 
-    [JSImport("Canvas.createCanvas", "avalonia.js")]
+    [JSImport("Canvas.createCanvas", "avalonia.ts")]
     public static partial JSObject CreateCanvas(JSObject container);
 
     [JSImport("Canvas.Foo", "avalonia.ts")]
-    internal static partial void Foo(JSObject canvas);
+    public static partial void Foo(JSObject canvas);
 
     [JSImport("Canvas.initGL", "avalonia.ts")]
     internal static partial JSObject InitGL(JSObject canvas, string canvasId);