AnyCPU - Add CefRuntime.SubscribeAnyCpuAssemblyResolver/LoadCefSharpCoreRuntimeAnyCpu

Simplify using CefSharp when targeting AnyCPU, it's now possible to include this as library code
now that CefSharp.dll targets AnyCPU.

There is no .Net Core/.Net 5.0 implementation of this class as the CefSharp.Core.Runtime.dll
is already loaded dynamically based on architecture.

- Call CefRuntime.LoadCefSharpCoreRuntimeAnyCpu to immediately load the CefSharp.Core.Runtime.dll
and all dependant resources will be loaded based on this instance
- Call LoadCefSharpCoreRuntimeAnyCpu.SubscribeAnyCpuAssemblyResolver to use load assembly
  when required.

Author: amaitland

CefSharp/CefRuntime.cs

@@ -0,0 +1,113 @@
+// Copyright © 2021 The CefSharp Authors. All rights reserved.
+//
+// Use of this source code is governed by a BSD-style license that can be found in the LICENSE file.
+
+using System;
+using System.IO;
+using System.Reflection;
+
+namespace CefSharp
+{
+    /// <summary>
+    /// CefRuntime - Used to simplify loading of the CefSharp architecture specific resources.
+    /// Typical use case would be when you are targeting AnyCPU
+    /// </summary>
+    public static class CefRuntime
+    {
+        private static ResolveEventHandler currentDomainAssemblyResolveHandler;
+
+        /// <summary>
+        /// When using AnyCPU the architecture specific version of CefSharp.Core.Runtime.dll
+        /// needs to be loaded (x64/x86).
+        /// This method subscribes to the <see cref="AppDomain.AssemblyResolve"/> event
+        /// for <see cref="AppDomain.CurrentDomain"/> and loads the CefSharp.Core.Runtime.dll
+        /// based on <see cref="Environment.Is64BitProcess"/>.
+        /// This method MUST be called before you call Cef.Initialize, create your first ChromiumWebBrowser instance, basically
+        /// before anything CefSharp related happens. This method is part of CefSharp.dll which is an AnyCPU library and
+        /// doesn't have any references to the CefSharp.Core.Runtime.dll so it's safe to use.
+        /// </summary>
+        /// <param name="basePath">
+        /// The path containing the x64/x86 folders which contain the CefSharp/CEF resources.
+        /// If null then AppDomain.CurrentDomain.SetupInformation.ApplicationBase will be used as the path.
+        /// (</param>
+        public static void SubscribeAnyCpuAssemblyResolver(string basePath = null)
+        {
+            if(currentDomainAssemblyResolveHandler != null)
+            {
+                throw new Exception("UseAnyCpuAssemblyResolver has already been called, call ");
+            }
+
+            if(basePath == null)
+            {
+                basePath = AppDomain.CurrentDomain.SetupInformation.ApplicationBase;
+            }
+
+            currentDomainAssemblyResolveHandler = (sender, args) =>
+            {
+                if (args.Name.StartsWith("CefSharp.Core.Runtime"))
+                {
+                    string assemblyName = args.Name.Split(new[] { ',' }, 2)[0] + ".dll";
+                    string archSpecificPath = Path.Combine(basePath,
+                                                           Environment.Is64BitProcess ? "x64" : "x86",
+                                                           assemblyName);
+
+                    return File.Exists(archSpecificPath)
+                               ? System.Reflection.Assembly.LoadFile(archSpecificPath)
+                               : null;
+                }
+
+                return null;
+            };
+
+            AppDomain.CurrentDomain.AssemblyResolve += currentDomainAssemblyResolveHandler;
+        }
+
+        /// <summary>
+        /// Unsubscribe  from the <see cref="AppDomain.AssemblyResolve"/> event
+        /// for <see cref="AppDomain.CurrentDomain"/> that was added in <see cref="UseAnyCpuAssemblyResolver"/>
+        /// </summary>
+        public static void UnsubscribeAnyCpuAssemblyResolver()
+        {
+            AppDomain.CurrentDomain.AssemblyResolve -= currentDomainAssemblyResolveHandler;
+
+            currentDomainAssemblyResolveHandler = null;
+        }
+
+        /// <summary>
+        /// When using AnyCPU the architecture specific version of CefSharp.Core.Runtime.dll
+        /// needs to be loaded (x64/x86).
+        /// This method calls <see cref="Assembly.LoadFile(string)"/> to immediately load CefSharp.Core.Runtime.dll
+        /// based on <see cref="Environment.Is64BitProcess"/>.
+        /// This method MUST be called before you call Cef.Initialize, create your first ChromiumWebBrowser instance, basically
+        /// before anything CefSharp related happens. This method is part of CefSharp.dll which is an AnyCPU library and
+        /// doesn't have any references to the CefSharp.Core.Runtime.dll so it's safe to use.
+        /// </summary>
+        /// <param name="basePath">
+        /// The path containing the x64/x86 folders which contain the CefSharp/CEF resources.
+        /// If null then AppDomain.CurrentDomain.SetupInformation.ApplicationBase will be used as the path.
+        /// (</param>
+        public static void LoadCefSharpCoreRuntimeAnyCpu(string basePath = null)
+        {
+            const string assemblyName = "CefSharp.Core.Runtime.dll";
+
+            if (basePath == null)
+            {
+                basePath = AppDomain.CurrentDomain.SetupInformation.ApplicationBase;
+            }
+
+            var env = Environment.Is64BitProcess ? "x64" : "x86";
+            string archSpecificPath = Path.Combine(basePath,
+                                                   env,
+                                                   assemblyName);
+
+            if (File.Exists(archSpecificPath))
+            {
+                Assembly.LoadFile(archSpecificPath);
+            }
+            else
+            {
+                throw new FileNotFoundException("Unable to load for arch " + env, archSpecificPath);
+            }
+        }
+    }
+}

CefSharp/CefSharp.csproj

@@ -86,6 +86,7 @@
     <Compile Include="Callback\TaskPrintToPdfCallback.cs" />
     <Compile Include="Callback\TaskResolveCallback.cs" />
     <Compile Include="CdmRegistration.cs" />
+    <Compile Include="CefRuntime.cs" />
     <Compile Include="DefaultApp.cs" />
     <Compile Include="DevToolsExtensions.cs" />
     <Compile Include="DevTools\DevToolsClient.cs" />

CefSharp/CefSharp.netcore.csproj

@@ -42,6 +42,7 @@
   </ItemGroup>
 
   <ItemGroup>
+    <Compile Remove="CefRuntime.cs" />
     <Compile Remove="DevTools\DevToolsClient.Generated.cs" />
     <Compile Remove="Internals\Partial\ChromiumWebBrowser.Partial.cs" />
   </ItemGroup>