Managed COM sample for .NET Core 3.0 (#857)

* Managed COM sample for .NET Core 3.0

* Feedback

Author: AaronRobinsonMSFT

core/extensions/COMServerDemo/COMClient/COMClient.csproj

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+<Project Sdk="Microsoft.NET.Sdk">
+
+  <PropertyGroup>
+    <OutputType>Exe</OutputType>
+    <TargetFramework>netcoreapp3.0</TargetFramework>
+  </PropertyGroup>
+
+  <ItemGroup>
+    <!-- Used in lieu of a Primary Interop Assembly (PIA) -->
+    <Compile Include="../COMContract/*.cs" />
+  </ItemGroup>
+
+</Project>

core/extensions/COMServerDemo/COMClient/Program.cs

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+using System;
+using System.Runtime.InteropServices;
+
+namespace COMClient
+{
+    class Program
+    {
+        static void Main(string[] args)
+        {
+            var server = new Activation.Server();
+
+            var pi = server.ComputePi();
+            Console.WriteLine($"\u03C0 = {pi}");
+        }
+    }
+
+    // The following classes are typically defined in a PIA, but for this example
+    // are being defined here to simplify the scenario.
+    namespace Activation
+    {
+        /// <summary>
+        /// Managed definition of CoClass 
+        /// </summary>
+        [ComImport]
+        [CoClass(typeof(ServerClass))]
+        [Guid(ContractGuids.ServerInterface)] // By TlbImp convention, set this to the GUID of the parent interface
+        internal interface Server : IServer
+        {
+        }
+
+        /// <summary>
+        /// Managed activation for CoClass
+        /// </summary>
+        [ComImport]
+        [Guid(ContractGuids.ServerClass)]
+        internal class ServerClass
+        {
+        }
+    }
+}

core/extensions/COMServerDemo/COMContract/ContractGuids.cs

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+internal sealed class ContractGuids
+{
+    public const string ServerClass = "DB1797F5-7198-4411-8563-D05F4E904956";
+    public const string ServerInterface = "BA9AC84B-C7FC-41CF-8B2F-1764EB773D4B";
+}

core/extensions/COMServerDemo/COMContract/IServer.cs

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+using System;
+using System.Runtime.InteropServices;
+
+[ComVisible(true)]
+[Guid(ContractGuids.ServerInterface)]
+[InterfaceType(ComInterfaceType.InterfaceIsIUnknown)]
+public interface IServer
+{
+    /// <summary>
+    /// Compute the value of the constant Pi.
+    /// </summary>
+    double ComputePi();
+}

core/extensions/COMServerDemo/COMServer/COMServer.csproj

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+<Project Sdk="Microsoft.NET.Sdk">
+
+  <PropertyGroup>
+    <!--
+        COM servers must define a framework to use in situations where a CLR instance is not already present in the process.
+        Note that since the COM server may be activated in a process where the CLR must be activated, both the projects
+        *.runtimeconfig.json and *.deps.json files must be bundled with the server itself.
+        
+        In the following example, the following files are needed to deploy the COM server:
+            COMServer.comhost.dll
+            COMServer.dll
+            COMServer.deps.json
+            COMServer.runtimeconfig.json
+    -->
+    <TargetFramework>netcoreapp3.0</TargetFramework>
+    
+    <!-- Indicate the assembly is providing a COM server -->
+    <UseComHost>True</UseComHost>
+  </PropertyGroup>
+
+  <ItemGroup>
+    <!-- Used in lieu of a Primary Interop Assembly (PIA) -->
+    <Compile Include="../COMContract/*.cs" />
+  </ItemGroup>
+
+  <Target Name="ServerUsage"
+          AfterTargets="Build">
+    <Message Importance="High" Text="%0a************************************%0a*** $(MSBuildProjectName) usage instructions ***%0a************************************" />
+    <Message Importance="High" Text="The server must be COM registered in order to activate.%0aThe following commands must be executed from an elevated command prompt." />
+    <Message Importance="High" Text="Register:%0a    regsvr32.exe &quot;$(ProjectDir)$(OutputPath)$(ComHostFileName)&quot;" />
+    <Message Importance="High" Text="Unregister:%0a    regsvr32.exe /u &quot;$(ProjectDir)$(OutputPath)$(ComHostFileName)&quot;" />
+  </Target>
+
+</Project>

core/extensions/COMServerDemo/COMServer/Server.cs

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+using System;
+using System.Runtime.InteropServices;
+
+namespace COMServer
+{
+    [ComVisible(true)]
+    [Guid(ContractGuids.ServerClass)]
+    public class Server : IServer
+    {
+        double IServer.ComputePi()
+        {
+            double sum = 0.0;
+            int sign = 1;
+            for (int i = 0; i < 1024; ++i)
+            {
+                sum += sign / (2.0 * i + 1.0);
+                sign *= -1;
+            }
+
+            return 4.0 * sum;
+        }
+    }
+}

core/extensions/COMServerDemo/NuGet.config

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+<?xml version="1.0" encoding="utf-8"?>
+<configuration>
+  <packageRestore>
+    <add key="enabled" value="True" />
+  </packageRestore>
+  <packageSources>
+    <clear />
+    <add key="nuget.org" value="https://api.nuget.org/v3/index.json" />
+  </packageSources>
+  <activePackageSource>
+    <add key="All" value="(Aggregate source)" />
+  </activePackageSource>
+</configuration>

core/extensions/COMServerDemo/ReadMe.md

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+COM Server Demo
+================
+
+This is a basic example of providing a managed COM server in .NET Core 3.0. Documentation on the inner workings of activation can be found [here](https://github.com/dotnet/core-setup/blob/master/Documentation/design-docs/COM-activation.md).
+
+Key Features
+------------
+
+Demonstrates how to provide a COM server in .NET Core 3.0 Preview 5 or later.
+
+Addtional comments are contained in source and project files.
+
+Build and Run
+-------------
+
+The project will only build and run on the Windows platform.
+
+1) Install .NET Core 3.0 Preview 5 or later.
+
+1) Navigate to the root directory and run `dotnet.exe build`.
+
+1) Follow the instructions for COM server registration that were emitted during the build.
+
+1) Navigate to `COMClient/` and run `dotnet.exe run`.
+
+**Note** Remember to unregister the COM server when the demo is complete.

core/extensions/COMServerDemo/build.proj

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+<Project Sdk="Microsoft.Build.Traversal">
+  <ItemGroup>
+    <ProjectReference Include="COMClient/*.csproj" />
+    <ProjectReference Include="COMServer/*.csproj" />
+  </ItemGroup>
+</Project>

core/extensions/COMServerDemo/global.json

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+{
+  "msbuild-sdks": {
+    "Microsoft.Build.Traversal": "1.0.52"
+  }
+}