Add telemetry data points for .NET Core 2.0

Author: William Li

src/Tasks/Microsoft.NET.Build.Tasks/build/Microsoft.NET.TargetFrameworkInference.targets

@@ -102,6 +102,10 @@ Copyright (c) .NET Foundation. All rights reserved.
                  FormatArguments="$([MSBuild]::Escape('$(TargetFramework)'))" />
   </Target>
 
+  <Target Name="_CollectTargetFrameworkForTelemetry" AfterTargets="_CheckForUnsupportedTargetFramework">
+    <Telemetry EventName="TargetFramework" EventData="version=$([MSBuild]::Escape('$(TargetFrameworkMoniker)'))" />
+  </Target>
+
   <!-- 
     Don't leave TargetFrameworkVersion empty if it still hasn't been determined. We will trigger the error above,
     but we need this to be a valid version so that our error message does not get pre-empted by failure to interpret

test/Microsoft.NET.Build.Tests/GivenThatWeWantToBuildANetCoreAppForTelemetry.cs

@@ -0,0 +1,75 @@
+using FluentAssertions;
+using Microsoft.NET.TestFramework;
+using Microsoft.NET.TestFramework.Assertions;
+using Microsoft.NET.TestFramework.Commands;
+using Microsoft.NET.TestFramework.ProjectConstruction;
+using System;
+using System.IO;
+using Xunit;
+using Xunit.Abstractions;
+using System.Reflection;
+
+namespace Microsoft.NET.Build.Tests
+{
+    public class GivenThatWeWantToBuildANetCoreAppAndPassingALogger : SdkTest
+    {
+        public GivenThatWeWantToBuildANetCoreAppAndPassingALogger(ITestOutputHelper log) : base(log)
+        {
+        }
+
+        [Fact]
+        public void It_collects_TargetFramework_version()
+        {
+            string targetFramework = "netcoreapp1.0";
+            var testProject = new TestProject()
+            {
+                Name = "FrameworkTargetTelemetryTest",
+                TargetFrameworks = targetFramework,
+                IsSdkProject = true,
+            };
+            Type loggerType = typeof(LogTelemetryToStdOutForTest);
+            var TelemetryTestLogger = new[]
+                {
+                    $"/Logger:{loggerType.FullName},{loggerType.GetTypeInfo().Assembly.Location}"
+                };
+            var testAsset = _testAssetsManager.CreateTestProject(testProject)
+                .Restore(Log, testProject.Name, TelemetryTestLogger);
+
+            var buildCommand = new BuildCommand(Log, Path.Combine(testAsset.TestRoot, testProject.Name));
+
+            buildCommand
+                .Execute(TelemetryTestLogger)
+                .StdOut.Should()
+                .Contain("{\"EventName\":\"TargetFramework\",\"Properties\":{\"version\":\".NETCoreApp,Version=v1.0\"}");
+        }
+
+        [Fact]
+        public void It_collects_multi_TargetFramework_version()
+        {
+            string targetFramework = "net46;netcoreapp1.1";
+
+            var testProject = new TestProject()
+            {
+                Name = "MultitargetTelemetry",
+                TargetFrameworks = targetFramework,
+                IsSdkProject = true,
+            };
+            Type loggerType = typeof(LogTelemetryToStdOutForTest);
+            var TelemetryTestLogger = new[]
+                {
+                    $"/Logger:{loggerType.FullName},{loggerType.GetTypeInfo().Assembly.Location}"
+                };
+            var testAsset = _testAssetsManager.CreateTestProject(testProject)
+                .Restore(Log, testProject.Name, TelemetryTestLogger);
+
+            var buildCommand = new BuildCommand(Log, Path.Combine(testAsset.TestRoot, testProject.Name));
+
+            buildCommand
+                .Execute(TelemetryTestLogger)
+                .StdOut.Should()
+                .Contain("{\"EventName\":\"TargetFramework\",\"Properties\":{\"version\":\".NETFramework,Version=v4.6\"}")
+                .And
+                .Contain("{\"EventName\":\"TargetFramework\",\"Properties\":{\"version\":\".NETCoreApp,Version=v1.1\"}");
+        }
+    }
+}

test/Microsoft.NET.Build.Tests/LogTelemetryToStdOutForTest.cs

@@ -0,0 +1,31 @@
+// Copyright (c) .NET Foundation and contributors. All rights reserved.
+// Licensed under the MIT license. See LICENSE file in the project root for full license information.
+
+using System;
+using Microsoft.Build.Framework;
+using Microsoft.Build.Utilities;
+using NuGet.Protocol;
+
+namespace Microsoft.NET.Build.Tests
+{
+    public sealed class LogTelemetryToStdOutForTest : Logger
+    {
+
+        public LogTelemetryToStdOutForTest()
+        {
+        }
+
+        public override void Initialize(IEventSource eventSource)
+        {
+            if (eventSource is IEventSource2 eventSource2)
+            {
+                eventSource2.TelemetryLogged += OnTelemetryLogged;
+            }
+        }
+
+        private void OnTelemetryLogged(object sender, TelemetryEventArgs args)
+        {
+            Console.WriteLine(args.ToJson());
+        }
+    }
+}