Handling Multiple TargetFrameworks through BuildProperties (#567)

* adding a sample project with plural form of TargetFrameworks for debugging purpose

* add --framework argument to RunCommand

* Pass down "framework" as a BuildProperty if not already defined in the YAML

* Do no throw anymore when multiple TargetFrameworks are found, if one was specified as a BuildProperty

* replicating Signature change on code base (that does not look like a good idea)

* adding comment to be explicit on what this does

* Check that the specified BuildProperties["TargetFramework"] is on of the TargetFrameworks

* add launchSettings for debug

* Create a BuildCommandArguments for the BuildCommand / add a "framework" options to it and move some logic to the CommandHandler (just like the RunCommand)

* add "-f {framework}" to dotnet publish if a TargetFramework BuildProperties exists

* Create a GenerateCommandArguments for the GenerateCommand / add a "framework" options to it and move some logic to the CommandHandler

* Create a PushCommandArguments for the PushCommand / add a "framework" options to it and move some logic to the CommandHandler

* Create a UndeployCommandArguments for the UndeployCommand / add a "framework" options to it and move some logic to the CommandHandler

* Create a DeployCommandArguments for the DeployCommand / add a "framework" options to it and move some logic to the CommandHandler

* framework is now an optional parameter defaulted to null

Co-authored-by: Justin Kotalik <jukotali@microsoft.com>

* Change sample to use LTS only

* Make "framework" argument nullable / optional / defaulted to null

* remove "Force" from "PushCommand" and "PushCommandArguments" if it's not used

* re-use the equivalent message than "dotnet run" on a project with multiple TargetFrameworks

* Create a StandardOptions for Framework

* Remove unused StandardOption.Force and add StandardOption.CreateForce with customizable "description"

* Use StandardOptions.Framework in various commands

* use StandardOptions.Force ni various commands

* Create a new InitCommandArguments and re-use the same OutputContext like the other Commands

* prefer type alias (String.IsNullOrEmpty => string.IsNullOrEmpty), not sure if it was intended

* Adding assets for E2E about multi-targetframeworks that returns the current TargetFramework on every HttpRequest

* Adding test for "tye run" with either buildProperties in the yaml or framework passed directly to ApplicationFactory.CreateAsync

* Add test and testasset project for both TargetFrameworks and TargetFramework

* Always overwrite the TargetFramework if one is specified from the CLI (like dotnet CLi) even if it means it wont build / run etc ....

* Test the ability to override TargetFramework from CLI even if define in csproj or in yaml

* Consistency over ApplicationFactory.CreateAsync in all E2E tests

* rename testasset project to multi-targetframeworks to match generated Dockerfile

* Add E2E for tye build when project uses multi-targetframeworks

* Adding test directly for ApplicationFactory to check that it overrides YAML existing buildProperties

* Adding test to make sure it still throw if there's no explicit TargetFramework or that it is one of the predefined one

* Adding test for ApplicationFactory.CreateAsync with a framework if nothing is set in yaml

* make cli arguments class private

* review: remove extra line

* review: remove 'framework' notion from Undeploy

* Fix project evaluation of multi-targetd projects

* Fixup a few more tests

* Comment updates

* Ensure TFM is only applied for multi-targeting projects

Co-authored-by: Justin Kotalik <jukotali@microsoft.com>
Co-authored-by: John Luo <johluo@microsoft.com>

samples/app-with-targetframeworks/MultipleTargetFrameworks/MultipleTargetFrameworks.csproj

@@ -0,0 +1,11 @@
+<Project Sdk="Microsoft.NET.Sdk.Web">
+
+  <PropertyGroup>
+    <TargetFrameworks>netcoreapp3.1;netcoreapp2.1</TargetFrameworks>
+  </PropertyGroup>
+
+  <ItemGroup Condition="'$(TargetFramework)' != 'netcoreapp3.1'">
+    <PackageReference Include="Microsoft.AspNetCore.App" />
+  </ItemGroup>
+
+</Project>

samples/app-with-targetframeworks/MultipleTargetFrameworks/Program.cs

@@ -0,0 +1,33 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Threading.Tasks;
+using Microsoft.AspNetCore;
+using Microsoft.AspNetCore.Hosting;
+using Microsoft.Extensions.Configuration;
+using Microsoft.Extensions.Hosting;
+using Microsoft.Extensions.Logging;
+
+namespace MultipleTargetFrameworks
+{
+    public class Program
+    {
+        public static void Main(string[] args)
+        {
+            CreateHostBuilder(args).Build().Run();
+        }
+
+#if NETCOREAPP3_1
+        public static IHostBuilder CreateHostBuilder(string[] args) =>
+            Host.CreateDefaultBuilder(args)
+                .ConfigureWebHostDefaults(webBuilder =>
+                {
+                    webBuilder.UseStartup<Startup>();
+                });
+#else
+        public static IWebHostBuilder CreateHostBuilder(string[] args) =>
+            WebHost.CreateDefaultBuilder(args)
+                .UseStartup<Startup>();
+#endif
+    }
+}

samples/app-with-targetframeworks/MultipleTargetFrameworks/Properties/launchSettings.json

@@ -0,0 +1,30 @@
+{
+  "$schema": "http://json.schemastore.org/launchsettings.json",
+  "iisSettings": {
+    "windowsAuthentication": false,
+    "anonymousAuthentication": true,
+    "iisExpress": {
+      "applicationUrl": "http://localhost:45835",
+      "sslPort": 44389
+    }
+  },
+  "profiles": {
+    "IIS Express": {
+      "commandName": "IISExpress",
+      "launchBrowser": true,
+      "launchUrl": "weatherforecast",
+      "environmentVariables": {
+        "ASPNETCORE_ENVIRONMENT": "Development"
+      }
+    },
+    "MultipleTargetFrameworks": {
+      "commandName": "Project",
+      "launchBrowser": true,
+      "launchUrl": "weatherforecast",
+      "applicationUrl": "https://localhost:5001;http://localhost:5000",
+      "environmentVariables": {
+        "ASPNETCORE_ENVIRONMENT": "Development"
+      }
+    }
+  }
+}

samples/app-with-targetframeworks/MultipleTargetFrameworks/Startup.cs

@@ -0,0 +1,42 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Threading.Tasks;
+using Microsoft.AspNetCore.Builder;
+using Microsoft.AspNetCore.Hosting;
+using Microsoft.AspNetCore.Http;
+using Microsoft.AspNetCore.HttpsPolicy;
+using Microsoft.AspNetCore.Mvc;
+using Microsoft.Extensions.Configuration;
+using Microsoft.Extensions.DependencyInjection;
+using Microsoft.Extensions.Hosting;
+using Microsoft.Extensions.Logging;
+
+namespace MultipleTargetFrameworks
+{
+    public class Startup
+    {
+        public Startup(IConfiguration configuration)
+        {
+            Configuration = configuration;
+        }
+
+        public IConfiguration Configuration { get; }
+
+        // This method gets called by the runtime. Use this method to add services to the container.
+        public void ConfigureServices(IServiceCollection services)
+        {
+        }
+
+        // This method gets called by the runtime. Use this method to configure the HTTP request pipeline.
+        public void Configure(IApplicationBuilder app)
+        {
+            app.UseHttpsRedirection();
+#if NETCOREAPP3_1
+            app.Run(async context => await context.Response.WriteAsync("NETCOREAPP3_1"));
+#else
+            app.Run(async context => await context.Response.WriteAsync("NETCOREAPP2_2"));
+#endif
+        }
+    }
+}

samples/app-with-targetframeworks/MultipleTargetFrameworks/appsettings.Development.json

@@ -0,0 +1,9 @@
+{
+  "Logging": {
+    "LogLevel": {
+      "Default": "Information",
+      "Microsoft": "Warning",
+      "Microsoft.Hosting.Lifetime": "Information"
+    }
+  }
+}

samples/app-with-targetframeworks/MultipleTargetFrameworks/appsettings.json

@@ -0,0 +1,10 @@
+{
+  "Logging": {
+    "LogLevel": {
+      "Default": "Information",
+      "Microsoft": "Warning",
+      "Microsoft.Hosting.Lifetime": "Information"
+    }
+  },
+  "AllowedHosts": "*"
+}

samples/app-with-targetframeworks/app-with-targetframeworks.sln

@@ -0,0 +1,34 @@
+
+Microsoft Visual Studio Solution File, Format Version 12.00
+# Visual Studio 15
+VisualStudioVersion = 15.0.26124.0
+MinimumVisualStudioVersion = 15.0.26124.0
+Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "MultipleTargetFrameworks", "MultipleTargetFrameworks\MultipleTargetFrameworks.csproj", "{D67C994A-74B0-4A15-BE84-E0518EEF3F74}"
+EndProject
+Global
+	GlobalSection(SolutionConfigurationPlatforms) = preSolution
+		Debug|Any CPU = Debug|Any CPU
+		Debug|x64 = Debug|x64
+		Debug|x86 = Debug|x86
+		Release|Any CPU = Release|Any CPU
+		Release|x64 = Release|x64
+		Release|x86 = Release|x86
+	EndGlobalSection
+	GlobalSection(SolutionProperties) = preSolution
+		HideSolutionNode = FALSE
+	EndGlobalSection
+	GlobalSection(ProjectConfigurationPlatforms) = postSolution
+		{D67C994A-74B0-4A15-BE84-E0518EEF3F74}.Debug|Any CPU.ActiveCfg = Debug|Any CPU
+		{D67C994A-74B0-4A15-BE84-E0518EEF3F74}.Debug|Any CPU.Build.0 = Debug|Any CPU
+		{D67C994A-74B0-4A15-BE84-E0518EEF3F74}.Debug|x64.ActiveCfg = Debug|Any CPU
+		{D67C994A-74B0-4A15-BE84-E0518EEF3F74}.Debug|x64.Build.0 = Debug|Any CPU
+		{D67C994A-74B0-4A15-BE84-E0518EEF3F74}.Debug|x86.ActiveCfg = Debug|Any CPU
+		{D67C994A-74B0-4A15-BE84-E0518EEF3F74}.Debug|x86.Build.0 = Debug|Any CPU
+		{D67C994A-74B0-4A15-BE84-E0518EEF3F74}.Release|Any CPU.ActiveCfg = Release|Any CPU
+		{D67C994A-74B0-4A15-BE84-E0518EEF3F74}.Release|Any CPU.Build.0 = Release|Any CPU
+		{D67C994A-74B0-4A15-BE84-E0518EEF3F74}.Release|x64.ActiveCfg = Release|Any CPU
+		{D67C994A-74B0-4A15-BE84-E0518EEF3F74}.Release|x64.Build.0 = Release|Any CPU
+		{D67C994A-74B0-4A15-BE84-E0518EEF3F74}.Release|x86.ActiveCfg = Release|Any CPU
+		{D67C994A-74B0-4A15-BE84-E0518EEF3F74}.Release|x86.Build.0 = Release|Any CPU
+	EndGlobalSection
+EndGlobal

samples/app-with-targetframeworks/tye.yaml

@@ -0,0 +1,13 @@
+# tye application configuration file
+# read all about it at https://github.com/dotnet/tye
+#
+# when you've given us a try, we'd love to know what you think:
+#    https://aka.ms/AA7q20u
+#
+name: app-with-targetframeworks
+services:
+- name: multipletargetframeworks
+  project: MultipleTargetFrameworks/MultipleTargetFrameworks.csproj
+  buildProperties:
+  - name: TargetFramework
+    value: netcoreapp3.1

src/Microsoft.Tye.Core/ApplicationFactory.cs

@@ -17,7 +17,7 @@ namespace Microsoft.Tye
 {
     public static class ApplicationFactory
     {
-        public static async Task<ApplicationBuilder> CreateAsync(OutputContext output, FileInfo source, ApplicationFactoryFilter? filter = null)
+        public static async Task<ApplicationBuilder> CreateAsync(OutputContext output, FileInfo source, string? framework = null, ApplicationFactoryFilter? filter = null)
         {
             if (source is null)
             {
@@ -104,7 +104,10 @@ namespace Microsoft.Tye
                         sb.AppendLine($"        <MicrosoftTye_ProjectServices " +
                             $"Include=\"{project.ProjectFullPath}\" " +
                             $"Name=\"{project.Name}\" " +
-                            $"BuildProperties=\"{(project.BuildProperties.Any() ? project.BuildProperties.Select(kvp => $"{kvp.Name}={kvp.Value}").Aggregate((a, b) => a + ";" + b) : string.Empty)}\" />");
+                            $"BuildProperties=\"" +
+                                $"{(project.BuildProperties.Any() ? project.BuildProperties.Select(kvp => $"{kvp.Name}={kvp.Value}").Aggregate((a, b) => a + ";" + b) : string.Empty)}" +
+                                $"{(string.IsNullOrEmpty(framework) ? string.Empty : $";TargetFramework={framework}")}" +
+                            $"\" />");
                     }
                     sb.AppendLine(@"    </ItemGroup>");
 
@@ -124,7 +127,12 @@ namespace Microsoft.Tye
                         "dotnet",
                         $"build " +
                             $"\"{projectPath}\" " +
+                            // CustomAfterMicrosoftCommonTargets is imported by non-crosstargeting (single TFM) projects
                             $"/p:CustomAfterMicrosoftCommonTargets={Path.Combine(Path.GetDirectoryName(Assembly.GetExecutingAssembly().Location)!, "ProjectEvaluation.targets")} " +
+                            // CustomAfterMicrosoftCommonCrossTargetingTargets is imported by crosstargeting (multi-TFM) projects
+                            // This ensures projects properties are evaluated correctly. However, multi-TFM projects must specify
+                            // a specific TFM to build/run/publish and will otherwise throw an exception.
+                            $"/p:CustomAfterMicrosoftCommonCrossTargetingTargets={Path.Combine(Path.GetDirectoryName(Assembly.GetExecutingAssembly().Location)!, "ProjectEvaluation.targets")} " +
                             $"/nologo",
                         throwOnError: false,
                         workingDirectory: directory.DirectoryPath);
@@ -181,6 +189,7 @@ namespace Microsoft.Tye
                         {
                             project.BuildProperties.Add(buildProperty.Name, buildProperty.Value);
                         }
+
                         project.Replicas = configService.Replicas ?? 1;
 
                         project.Liveness = configService.Liveness != null ? GetProbeBuilder(configService.Liveness) : null;
@@ -198,6 +207,12 @@ namespace Microsoft.Tye
 
                         ProjectReader.ReadProjectDetails(output, project, projectMetadata[configService.Name]);
 
+                        if (framework != null && project.TargetFrameworks.Any())
+                        {
+                            // Only use the TargetFramework for the "--framework" if it's a multi-targeted project and an override is provided
+                            project.BuildProperties["TargetFramework"] = framework;
+                        }
+
                         // Do k8s by default.
                         project.ManifestInfo = new KubernetesManifestInfo();
                     }

src/Microsoft.Tye.Core/PublishProjectStep.cs

@@ -36,11 +36,15 @@ namespace Microsoft.Tye
             var outputDirectory = TempDirectory.Create();
 
             output.WriteDebugLine("Running 'dotnet publish'.");
-            output.WriteCommandLine("dotnet", $"publish \"{project.ProjectFile.FullName}\" -c Release -o \"{outputDirectory.DirectoryPath}\"");
+            var dotnetPublishArguments = project.BuildProperties.TryGetValue("TargetFramework", out var framework)
+                ? $"publish \"{project.ProjectFile.FullName}\" -c Release -f {framework} -o \"{outputDirectory.DirectoryPath}\""
+                : $"publish \"{project.ProjectFile.FullName}\" -c Release -o \"{outputDirectory.DirectoryPath}\"";
+
+            output.WriteCommandLine("dotnet", dotnetPublishArguments);
 
             var publishResult = await ProcessUtil.RunAsync(
                 $"dotnet",
-                $"publish \"{project.ProjectFile.FullName}\" -c Release -o \"{outputDirectory.DirectoryPath}\"",
+                dotnetPublishArguments,
                 project.ProjectFile.DirectoryName,
                 throwOnError: false);
 

src/Microsoft.Tye.Core/StandardOptions.cs

@@ -46,16 +46,18 @@ namespace Microsoft.Tye
             }
         }
 
-        public static Option Force
-        {
-            get
-            {
-                return new Option("--force", "Force overwrite of existing files")
-                {
-                    Argument = new Argument<bool>(),
-                };
-            }
-        }
+        public static Option Framework =>
+                    new Option(new string[] { "-f", "--framework" })
+                    {
+                        Description = "The target framework override to use for all cross-targeting projects with multiple TFMs. " +
+                            "This value must be a valid target framework for each individual cross-targeting project. " +
+                            "Non-crosstargeting projects will ignore this value. ",
+                        Argument = new Argument<string>("framework")
+                        {
+                            Arity = ArgumentArity.ExactlyOne
+                        },
+                        Required = false
+                    };
 
         public static Option Interactive
         {
@@ -224,5 +226,13 @@ namespace Microsoft.Tye
                 };
             }
         }
+
+        public static Option CreateForce(string descriptions) =>
+            new Option(new[] { "--force" })
+            {
+                Argument = new Argument<bool>(),
+                Description = descriptions,
+                Required = false
+            };
     }
 }

src/tye/ApplicationBuilderExtensions.cs

@@ -5,6 +5,7 @@
 using System;
 using System.Collections.Generic;
 using System.IO;
+using System.Linq;
 using System.Threading.Tasks;
 using Microsoft.Tye.Extensions;
 using Microsoft.Tye.Hosting.Model;
@@ -122,7 +123,17 @@ namespace Microsoft.Tye
                 {
                     if (project.TargetFrameworks.Length > 1)
                     {
-                        throw new InvalidOperationException($"Unable to run {project.Name}. Multi-targeted projects are not supported.");
+                        if (project.BuildProperties.TryGetValue("TargetFramework", out var targetFramework))
+                        {
+                            if (!project.TargetFrameworks.Contains(targetFramework))
+                            {
+                                throw new InvalidOperationException($"Unable to run {project.Name}. The specified TargetFramework is not one of the existing TargetFrameworks in the project.");
+                            }
+                        }
+                        else
+                        {
+                            throw new InvalidOperationException($"Unable to run {project.Name}. Your project targets multiple frameworks. Specify which framework to run using '--framework'.");
+                        }
                     }
 
                     if (project.RunCommand == null)

src/tye/BuildHost.cs

@@ -11,11 +11,9 @@ namespace Microsoft.Tye
 {
     public static class BuildHost
     {
-        public static async Task BuildAsync(IConsole console, FileInfo path, Verbosity verbosity, bool interactive, string[] tags)
+        public static async Task BuildAsync(OutputContext output, FileInfo path, bool interactive, string? framework = null, ApplicationFactoryFilter? filter = null)
         {
-            var output = new OutputContext(console, verbosity);
-            var filter = ApplicationFactoryFilter.GetApplicationFactoryFilter(tags);
-            var application = await ApplicationFactory.CreateAsync(output, path, filter);
+            var application = await ApplicationFactory.CreateAsync(output, path, framework, filter);
             if (application.Services.Count == 0)
             {
                 throw new CommandException($"No services found in \"{application.Source.Name}\"");

src/tye/GenerateHost.cs

@@ -13,18 +13,15 @@ namespace Microsoft.Tye
 {
     public static class GenerateHost
     {
-        public static async Task GenerateAsync(IConsole console, FileInfo path, Verbosity verbosity, bool interactive, string ns, string[] tags)
+        public static async Task GenerateAsync(OutputContext output, FileInfo path, bool interactive, string ns, string? framework = null, ApplicationFactoryFilter? filter = null)
         {
-            var output = new OutputContext(console, verbosity);
+            var application = await ApplicationFactory.CreateAsync(output, path, framework, filter);
 
-            output.WriteInfoLine("Loading Application Details...");
-            var filter = ApplicationFactoryFilter.GetApplicationFactoryFilter(tags);
-            var application = await ApplicationFactory.CreateAsync(output, path, filter);
             if (application.Services.Count == 0)
             {
                 throw new CommandException($"No services found in \"{application.Source.Name}\"");
             }
-            if (!String.IsNullOrEmpty(ns))
+            if (!string.IsNullOrEmpty(ns))
             {
                 application.Namespace = ns;
             }

src/tye/Program.BuildCommand.cs

@@ -2,6 +2,7 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 // See the LICENSE file in the project root for more information.
 
+using System;
 using System.Collections.Generic;
 using System.CommandLine;
 using System.CommandLine.Invocation;
@@ -20,22 +21,43 @@ namespace Microsoft.Tye
             {
                 CommonArguments.Path_Required,
                 StandardOptions.Interactive,
+                StandardOptions.Tags,
                 StandardOptions.Verbosity,
-                StandardOptions.Tags
+                StandardOptions.Framework,
             };
 
-            command.Handler = CommandHandler.Create<IConsole, FileInfo, Verbosity, bool, string[]>((console, path, verbosity, interactive, tags) =>
+            command.Handler = CommandHandler.Create<BuildCommandArguments>(args =>
             {
                 // Workaround for https://github.com/dotnet/command-line-api/issues/723#issuecomment-593062654
-                if (path is null)
+                if (args.Path is null)
                 {
                     throw new CommandException("No project or solution file was found.");
                 }
 
-                return BuildHost.BuildAsync(console, path, verbosity, interactive, tags);
+                var output = new OutputContext(args.Console, args.Verbosity);
+                output.WriteInfoLine("Loading Application Details...");
+
+                var filter = ApplicationFactoryFilter.GetApplicationFactoryFilter(args.Tags);
+
+                return BuildHost.BuildAsync(output, args.Path, args.Interactive, args.Framework, filter);
             });
 
             return command;
         }
+
+        private class BuildCommandArguments
+        {
+            public IConsole Console { get; set; } = default!;
+
+            public FileInfo Path { get; set; } = default!;
+
+            public Verbosity Verbosity { get; set; }
+
+            public string Framework { get; set; } = default!;
+
+            public bool Interactive { get; set; } = false;
+
+            public string[] Tags { get; set; } = Array.Empty<string>();
+        }
     }
 }

src/tye/Program.DeployCommand.cs

@@ -24,39 +24,37 @@ namespace Microsoft.Tye
                 StandardOptions.Interactive,
                 StandardOptions.Verbosity,
                 StandardOptions.Namespace,
+                StandardOptions.Framework,
                 StandardOptions.Tags,
+                StandardOptions.CreateForce("Override validation and force deployment.")
             };
 
-            command.AddOption(new Option(new[] { "-f", "--force" })
-            {
-                Description = "Override validation and force deployment.",
-                Required = false
-            });
-
-            command.Handler = CommandHandler.Create<IConsole, FileInfo, Verbosity, bool, bool, string, string[]>(async (console, path, verbosity, interactive, force, @namespace, tags) =>
+            command.Handler = CommandHandler.Create<DeployCommandArguments>(async args =>
             {
                 // Workaround for https://github.com/dotnet/command-line-api/issues/723#issuecomment-593062654
-                if (path is null)
+                if (args.Path is null)
                 {
                     throw new CommandException("No project or solution file was found.");
                 }
 
-                var output = new OutputContext(console, verbosity);
-
+                var output = new OutputContext(args.Console, args.Verbosity);
                 output.WriteInfoLine("Loading Application Details...");
 
-                var filter = ApplicationFactoryFilter.GetApplicationFactoryFilter(tags);
+                var filter = ApplicationFactoryFilter.GetApplicationFactoryFilter(args.Tags);
 
-                var application = await ApplicationFactory.CreateAsync(output, path, filter);
+                var application = await ApplicationFactory.CreateAsync(output, args.Path, args.Framework, filter);
                 if (application.Services.Count == 0)
                 {
                     throw new CommandException($"No services found in \"{application.Source.Name}\"");
                 }
-                if (!string.IsNullOrEmpty(@namespace))
+
+                if (!string.IsNullOrEmpty(args.Namespace))
                 {
-                    application.Namespace = @namespace;
+                    application.Namespace = args.Namespace;
                 }
-                await ExecuteDeployAsync(new OutputContext(console, verbosity), application, environment: "production", interactive, force);
+
+                var executeOutput = new OutputContext(args.Console, args.Verbosity);
+                await ExecuteDeployAsync(executeOutput, application, environment: "production", args.Interactive, args.Force);
             });
 
             return command;
@@ -132,5 +130,24 @@ namespace Microsoft.Tye
                 // No registry specified, and that's OK!
             }
         }
+
+        private class DeployCommandArguments
+        {
+            public IConsole Console { get; set; } = default!;
+
+            public FileInfo Path { get; set; } = default!;
+
+            public Verbosity Verbosity { get; set; }
+
+            public string Namespace { get; set; } = default!;
+
+            public bool Interactive { get; set; } = false;
+
+            public string Framework { get; set; } = default!;
+
+            public bool Force { get; set; } = false;
+
+            public string[] Tags { get; set; } = Array.Empty<string>();
+        }
     }
 }

src/tye/Program.GenerateCommand.cs

@@ -2,6 +2,7 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 // See the LICENSE file in the project root for more information.
 
+using System;
 using System.Collections.Generic;
 using System.CommandLine;
 using System.CommandLine.Invocation;
@@ -22,25 +23,48 @@ namespace Microsoft.Tye
                 StandardOptions.Interactive,
                 StandardOptions.Verbosity,
                 StandardOptions.Namespace,
-                StandardOptions.Tags
+                StandardOptions.Tags,
+                StandardOptions.Framework,
             };
 
             // This is a super-secret VIP-only command! It's useful for testing, but we're 
             // not documenting it right now.
             command.IsHidden = true;
 
-            command.Handler = CommandHandler.Create<IConsole, FileInfo, Verbosity, bool, string, string[]>((console, path, verbosity, interactive, @namespace, tags) =>
+            command.Handler = CommandHandler.Create<GenerateCommandArguments>(args =>
             {
                 // Workaround for https://github.com/dotnet/command-line-api/issues/723#issuecomment-593062654
-                if (path is null)
+                if (args.Path is null)
                 {
                     throw new CommandException("No project or solution file was found.");
                 }
 
-                return GenerateHost.GenerateAsync(console, path, verbosity, interactive, @namespace, tags);
+                var output = new OutputContext(args.Console, args.Verbosity);
+                output.WriteInfoLine("Loading Application Details...");
+
+                var filter = ApplicationFactoryFilter.GetApplicationFactoryFilter(args.Tags);
+
+                return GenerateHost.GenerateAsync(output, args.Path, args.Interactive, args.Namespace, args.Framework, filter);
             });
 
             return command;
         }
+
+        private class GenerateCommandArguments
+        {
+            public IConsole Console { get; set; } = default!;
+
+            public FileInfo Path { get; set; } = default!;
+
+            public Verbosity Verbosity { get; set; }
+
+            public bool Interactive { get; set; } = false;
+
+            public string Namespace { get; set; } = default!;
+
+            public string Framework { get; set; } = default!;
+
+            public string[] Tags { get; set; } = Array.Empty<string>();
+        }
     }
 }

src/tye/Program.InitCommand.cs

@@ -20,29 +20,34 @@ namespace Microsoft.Tye
             var command = new Command("init", "create a yaml manifest")
             {
                 CommonArguments.Path_Optional,
+                StandardOptions.CreateForce("Overrides the tye.yaml file if already present for project.")
             };
 
-            command.AddOption(new Option(new[] { "-f", "--force" })
-            {
-                Description = "Overrides the tye.yaml file if already present for project.",
-                Required = false
-            });
-
-            command.Handler = CommandHandler.Create<IConsole, FileInfo?, bool>((console, path, force) =>
+            command.Handler = CommandHandler.Create<InitCommandArguments>(args =>
             {
                 var watch = System.Diagnostics.Stopwatch.StartNew();
 
-                var outputFilePath = InitHost.CreateTyeFile(path, force);
-                console.Out.WriteLine($"Created '{outputFilePath}'.");
+                var output = new OutputContext(args.Console, args.Verbosity);
+                var outputFilePath = InitHost.CreateTyeFile(args.Path, args.Force);
+                output.WriteInfoLine($"Created '{outputFilePath}'.");
 
                 watch.Stop();
-
-                TimeSpan elapsedTime = watch.Elapsed;
-
-                console.Out.WriteLine($"Time Elapsed: {elapsedTime.Hours:00}:{elapsedTime.Minutes:00}:{elapsedTime.Seconds:00}:{elapsedTime.Milliseconds / 10:00}");
+                var elapsedTime = watch.Elapsed;
+                output.WriteInfoLine($"Time Elapsed: {elapsedTime.Hours:00}:{elapsedTime.Minutes:00}:{elapsedTime.Seconds:00}:{elapsedTime.Milliseconds / 10:00}");
             });
 
             return command;
         }
+
+        private class InitCommandArguments
+        {
+            public IConsole Console { get; set; } = default!;
+
+            public FileInfo Path { get; set; } = default!;
+
+            public Verbosity Verbosity { get; set; }
+
+            public bool Force { get; set; } = false;
+        }
     }
 }

src/tye/Program.PushCommand.cs

@@ -2,6 +2,7 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 // See the LICENSE file in the project root for more information.
 
+using System;
 using System.CommandLine;
 using System.CommandLine.Invocation;
 using System.IO;
@@ -18,41 +19,38 @@ namespace Microsoft.Tye
                 CommonArguments.Path_Required,
                 StandardOptions.Interactive,
                 StandardOptions.Verbosity,
-                StandardOptions.Tags
+                StandardOptions.Tags,
+                StandardOptions.Framework,
+                StandardOptions.CreateForce("Override validation and force push.")
             };
 
-            command.AddOption(new Option(new[] { "-f", "--force" })
-            {
-                Description = "Override validation and force push.",
-                Required = false
-            });
-
-            command.Handler = CommandHandler.Create<IConsole, FileInfo, Verbosity, bool, bool, string[]>(async (console, path, verbosity, interactive, force, tags) =>
+            command.Handler = CommandHandler.Create<PushCommandArguments>(async args =>
             {
                 // Workaround for https://github.com/dotnet/command-line-api/issues/723#issuecomment-593062654
-                if (path is null)
+                if (args.Path is null)
                 {
                     throw new CommandException("No project or solution file was found.");
                 }
 
-                var output = new OutputContext(console, verbosity);
-
+                var output = new OutputContext(args.Console, args.Verbosity);
                 output.WriteInfoLine("Loading Application Details...");
-                var filter = ApplicationFactoryFilter.GetApplicationFactoryFilter(tags);
 
-                var application = await ApplicationFactory.CreateAsync(output, path, filter);
+                var filter = ApplicationFactoryFilter.GetApplicationFactoryFilter(args.Tags);
+
+                var application = await ApplicationFactory.CreateAsync(output, args.Path, args.Framework, filter);
                 if (application.Services.Count == 0)
                 {
                     throw new CommandException($"No services found in \"{application.Source.Name}\"");
                 }
 
-                await ExecutePushAsync(new OutputContext(console, verbosity), application, environment: "production", interactive, force);
+                var executeOutput = new OutputContext(args.Console, args.Verbosity);
+                await ExecutePushAsync(output, application, environment: "production", args.Interactive);
             });
 
             return command;
         }
 
-        private static async Task ExecutePushAsync(OutputContext output, ApplicationBuilder application, string environment, bool interactive, bool force)
+        private static async Task ExecutePushAsync(OutputContext output, ApplicationBuilder application, string environment, bool interactive)
         {
             await application.ProcessExtensionsAsync(options: null, output, ExtensionContext.OperationKind.Deploy);
             ApplyRegistry(output, application, interactive, requireRegistry: true);
@@ -71,5 +69,20 @@ namespace Microsoft.Tye
 
             await executor.ExecuteAsync(application);
         }
+
+        private class PushCommandArguments
+        {
+            public IConsole Console { get; set; } = default!;
+
+            public FileInfo Path { get; set; } = default!;
+
+            public Verbosity Verbosity { get; set; }
+
+            public bool Interactive { get; set; } = false;
+
+            public string Framework { get; set; } = default!;
+
+            public string[] Tags { get; set; } = Array.Empty<string>();
+        }
     }
 }

src/tye/Program.RunCommand.cs

@@ -74,6 +74,7 @@ namespace Microsoft.Tye
                     Description = "Watches for code changes for all dotnet projects.",
                     Required = false
                 },
+                StandardOptions.Framework,
                 StandardOptions.Tags,
                 StandardOptions.Verbosity,
             };
@@ -92,7 +93,7 @@ namespace Microsoft.Tye
 
                 var filter = ApplicationFactoryFilter.GetApplicationFactoryFilter(args.Tags);
 
-                var application = await ApplicationFactory.CreateAsync(output, args.Path, filter);
+                var application = await ApplicationFactory.CreateAsync(output, args.Path, args.Framework, filter);
                 if (application.Services.Count == 0)
                 {
                     throw new CommandException($"No services found in \"{application.Source.Name}\"");
@@ -171,6 +172,8 @@ namespace Microsoft.Tye
 
             public bool Watch { get; set; }
 
+            public string Framework { get; set; } = default!;
+
             public string[] Tags { get; set; } = Array.Empty<string>();
         }
     }

src/tye/Program.UndeployCommand.cs

@@ -2,6 +2,7 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 // See the LICENSE file in the project root for more information.
 
+using System;
 using System.Collections.Generic;
 using System.CommandLine;
 using System.CommandLine.Invocation;
@@ -30,18 +31,40 @@ namespace Microsoft.Tye
                 },
             };
 
-            command.Handler = CommandHandler.Create<IConsole, FileInfo, Verbosity, string, bool, bool, string[]>((console, path, verbosity, @namespace, interactive, whatIf, tags) =>
+            command.Handler = CommandHandler.Create<UndeployCommandArguments>(args =>
             {
                 // Workaround for https://github.com/dotnet/command-line-api/issues/723#issuecomment-593062654
-                if (path is null)
+                if (args.Path is null)
                 {
                     throw new CommandException("No project or solution file was found.");
                 }
 
-                return UndeployHost.UndeployAsync(console, path, verbosity, @namespace, interactive, whatIf, tags);
+                var output = new OutputContext(args.Console, args.Verbosity);
+                output.WriteInfoLine("Loading Application Details...");
+
+                var filter = ApplicationFactoryFilter.GetApplicationFactoryFilter(args.Tags);
+
+                return UndeployHost.UndeployAsync(output, args.Path, args.Namespace, args.Interactive, args.WhatIf, filter);
             });
 
             return command;
         }
+
+        private class UndeployCommandArguments
+        {
+            public IConsole Console { get; set; } = default!;
+
+            public FileInfo Path { get; set; } = default!;
+
+            public Verbosity Verbosity { get; set; }
+
+            public string Namespace { get; set; } = default!;
+
+            public bool Interactive { get; set; } = false;
+
+            public bool WhatIf { get; set; } = false;
+
+            public string[] Tags { get; set; } = Array.Empty<string>();
+        }
     }
 }

src/tye/ProjectEvaluation.targets

@@ -1,15 +1,23 @@
 <Project>
-    <Target Name="MicrosoftTye_GetProjectMetadata" DependsOnTargets="Restore;ResolveReferences;ResolvePackageDependenciesDesignTime;PrepareResources;GetAssemblyAttributes" >
+    <PropertyGroup>
+       <!-- Single TFM projects -->
+      <MicrosoftTye_GetProjectMetadata_DependsOn>Restore;ResolveReferences;ResolvePackageDependenciesDesignTime;PrepareResources;PrepareResources;GetAssemblyAttributes</MicrosoftTye_GetProjectMetadata_DependsOn>
+      <!-- Multi TFM projects -->
+        <MicrosoftTye_GetProjectMetadata_DependsOn Condition="'$(IsCrossTargetingBuild)' == 'true'">Restore</MicrosoftTye_GetProjectMetadata_DependsOn>
+    </PropertyGroup>
+
+    <Target Name="MicrosoftTye_GetProjectMetadata" DependsOnTargets="$(MicrosoftTye_GetProjectMetadata_DependsOn)" >
         <PropertyGroup>
             <_MicrosoftTye_MetadataFile>$([System.IO.Path]::GetFullPath('$(IntermediateOutputPath)MicrosoftTye.ProjectMetadata.txt'))</_MicrosoftTye_MetadataFile>
-            <_MicrosoftTye_ProjectFrameworkReference>@(FrameworkReference, '%3B')</_MicrosoftTye_ProjectFrameworkReference>
+          <_MicrosoftTye_ProjectFrameworkReference>@(FrameworkReference, '%3B')</_MicrosoftTye_ProjectFrameworkReference>
+          <_MicrosoftTye_ProjectFrameworks>$(TargetFrameworks.Replace(';', '%3B'))</_MicrosoftTye_ProjectFrameworks>
         </PropertyGroup>
 
         <ItemGroup>
             <_MicrosoftTye_ProjectMetadata Include="AssemblyInformationalVersion: $(AssemblyInformationalVersion)" />
             <_MicrosoftTye_ProjectMetadata Include="InformationalVersion: $(InformationalVersion)" />
             <_MicrosoftTye_ProjectMetadata Include="Version: $(Version)" />
-            <_MicrosoftTye_ProjectMetadata Include="TargetFrameworks: $(TargetFrameworks)" />
+            <_MicrosoftTye_ProjectMetadata Include="TargetFrameworks: $(_MicrosoftTye_ProjectFrameworks)" />
             <_MicrosoftTye_ProjectMetadata Include="RunCommand: $(RunCommand)" />
             <_MicrosoftTye_ProjectMetadata Include="RunArguments: $(RunArguments)" />
             <_MicrosoftTye_ProjectMetadata Include="TargetPath: $(TargetPath)" />

src/tye/Properties/launchSettings.json

@@ -0,0 +1,9 @@
+{
+  "profiles": {
+    "tye": {
+      "commandName": "Project",
+      "commandLineArgs": "build --framework netcoreapp3.1",
+      "workingDirectory": "..\\..\\samples\\app-with-targetframeworks\\"
+    }
+  }
+}

src/tye/UndeployHost.cs

@@ -17,16 +17,12 @@ namespace Microsoft.Tye
 {
     public static class UndeployHost
     {
-        public static async Task UndeployAsync(IConsole console, FileInfo path, Verbosity verbosity, string @namespace, bool interactive, bool whatIf, string[] tags)
+        public static async Task UndeployAsync(OutputContext output, FileInfo path, string @namespace, bool interactive, bool whatIf, ApplicationFactoryFilter? filter = null)
         {
             var watch = System.Diagnostics.Stopwatch.StartNew();
 
-            var output = new OutputContext(console, verbosity);
+            var application = await ApplicationFactory.CreateAsync(output, path, null, filter);
 
-            output.WriteInfoLine("Loading Application Details...");
-
-            var filter = ApplicationFactoryFilter.GetApplicationFactoryFilter(tags);
-            var application = await ApplicationFactory.CreateAsync(output, path, filter);
             if (!string.IsNullOrEmpty(@namespace))
             {
                 application.Namespace = @namespace;

test/E2ETest/ApplicationFactoryTests.cs

@@ -1,4 +1,5 @@
-using System.IO;
+using System;
+using System.IO;
 using System.Linq;
 using System.Threading.Tasks;
 using Microsoft.Tye;
@@ -27,11 +28,12 @@ services:
 - name: test-project
   include: tye.yaml";
             var yamlFile = Path.Combine(projectDirectory.DirectoryPath, "tye.yaml");
-
             await File.WriteAllTextAsync(yamlFile, content);
+
             // Debug targets can be null if not specified, so make sure calling host.Start does not throw.
             var outputContext = new OutputContext(_sink, Verbosity.Debug);
-            var application = await ApplicationFactory.CreateAsync(outputContext, new FileInfo(yamlFile));
+            var projectFile = new FileInfo(yamlFile);
+            var application = await ApplicationFactory.CreateAsync(outputContext, projectFile);
 
             Assert.Empty(application.Services);
         }
@@ -52,7 +54,8 @@ services:
 
             // Debug targets can be null if not specified, so make sure calling host.Start does not throw.
             var outputContext = new OutputContext(_sink, Verbosity.Debug);
-            var application = await ApplicationFactory.CreateAsync(outputContext, new FileInfo(yamlFile));
+            var projectFile = new FileInfo(yamlFile);
+            var application = await ApplicationFactory.CreateAsync(outputContext, projectFile);
 
             Assert.Equal(5, application.Services.Count);
 
@@ -100,7 +103,8 @@ services:
 
             // Debug targets can be null if not specified, so make sure calling host.Start does not throw.
             var outputContext = new OutputContext(_sink, Verbosity.Debug);
-            var application = await ApplicationFactory.CreateAsync(outputContext, new FileInfo(yamlFile));
+            var projectFile = new FileInfo(yamlFile);
+            var application = await ApplicationFactory.CreateAsync(outputContext, projectFile);
 
             Assert.Equal(4, application.Services.Count);
             var redisService = application.Services.Single(s => s.Name == "redis");
@@ -121,5 +125,94 @@ services:
             var wrongProjectPath = Path.Combine(projectDirectory.DirectoryPath, "backend1/backend.csproj");
             Assert.Equal($"Failed to locate project: '{wrongProjectPath}'.", exception.Message);
         }
+
+        [Fact]
+        public async Task TargetFrameworkFromCliArgs()
+        {
+            using var projectDirectory = TestHelpers.CopyTestProjectDirectory(Path.Combine("multi-targetframeworks"));
+            var yamlFile = Path.Combine(projectDirectory.DirectoryPath, "tye-no-buildproperties.yaml");
+
+            // Debug targets can be null if not specified, so make sure calling host.Start does not throw.
+            var outputContext = new OutputContext(_sink, Verbosity.Debug);
+            var projectFile = new FileInfo(yamlFile);
+            var applicationBuilder = await ApplicationFactory.CreateAsync(outputContext, projectFile, "netcoreapp3.1");
+
+            Assert.Single(applicationBuilder.Services);
+            var service = applicationBuilder.Services.Single(s => s.Name == "multi-targetframeworks");
+
+            var containsTargetFramework = ((DotnetProjectServiceBuilder)service).BuildProperties.TryGetValue("TargetFramework", out var targetFramework);
+            Assert.True(containsTargetFramework);
+            Assert.Equal("netcoreapp3.1", targetFramework);
+        }
+
+        [Fact]
+        public async Task TargetFrameworkFromCliArgsOverwriteYaml()
+        {
+            using var projectDirectory = TestHelpers.CopyTestProjectDirectory(Path.Combine("multi-targetframeworks"));
+            var yamlFile = Path.Combine(projectDirectory.DirectoryPath, "tye-with-netcoreapp21.yaml");
+
+            // Debug targets can be null if not specified, so make sure calling host.Start does not throw.
+            var outputContext = new OutputContext(_sink, Verbosity.Debug);
+            var projectFile = new FileInfo(yamlFile);
+            var applicationBuilder = await ApplicationFactory.CreateAsync(outputContext, projectFile, "netcoreapp3.1");
+
+            Assert.Single(applicationBuilder.Services);
+            var service = applicationBuilder.Services.Single(s => s.Name == "multi-targetframeworks");
+
+            var containsTargetFramework = ((DotnetProjectServiceBuilder)service).BuildProperties.TryGetValue("TargetFramework", out var targetFramework);
+            Assert.True(containsTargetFramework);
+            Assert.Equal("netcoreapp3.1", targetFramework);
+        }
+
+        [Fact]
+        public async Task TargetFrameworkFromCliArgsDoesNotOverrideSingleTFM()
+        {
+            using var projectDirectory = TestHelpers.CopyTestProjectDirectory(Path.Combine("single-project"));
+            var yamlFile = Path.Combine(projectDirectory.DirectoryPath, "tye.yaml");
+
+            // Debug targets can be null if not specified, so make sure calling host.Start does not throw.
+            var outputContext = new OutputContext(_sink, Verbosity.Debug);
+            var projectFile = new FileInfo(yamlFile);
+            var applicationBuilder = await ApplicationFactory.CreateAsync(outputContext, projectFile, "net5.0");
+
+            Assert.Single(applicationBuilder.Services);
+            var service = applicationBuilder.Services.Single(s => s.Name == "test-project");
+
+            var containsTargetFramework = ((DotnetProjectServiceBuilder)service).BuildProperties.TryGetValue("TargetFramework", out var targetFramework);
+            Assert.False(containsTargetFramework);
+        }
+
+        [Fact]
+        public async Task ThrowIfNoSpecificTargetFramework()
+        {
+            using var projectDirectory = TestHelpers.CopyTestProjectDirectory(Path.Combine("multi-targetframeworks"));
+            var yamlFile = Path.Combine(projectDirectory.DirectoryPath, "tye-no-buildproperties.yaml");
+
+            // Debug targets can be null if not specified, so make sure calling host.Start does not throw.
+            var outputContext = new OutputContext(_sink, Verbosity.Debug);
+            var projectFile = new FileInfo(yamlFile);
+            var applicationBuilder = await ApplicationFactory.CreateAsync(outputContext, projectFile);
+
+            Assert.Single(applicationBuilder.Services);
+            var service = applicationBuilder.Services.Single(s => s.Name == "multi-targetframeworks");
+
+            var containsTargetFramework = ((DotnetProjectServiceBuilder)service).BuildProperties.TryGetValue("TargetFramework", out var targetFramework);
+            Assert.False(containsTargetFramework);
+
+            Assert.Throws<InvalidOperationException>(() => applicationBuilder.ToHostingApplication());
+        }
+
+        [Fact]
+        public async Task ThrowIfSpecifyTargetFrameworkNotDefinedIsCsproj()
+        {
+            using var projectDirectory = TestHelpers.CopyTestProjectDirectory(Path.Combine("multi-targetframeworks"));
+            var yamlFile = Path.Combine(projectDirectory.DirectoryPath, "tye-with-netcoreapp21.yaml");
+
+            // Debug targets can be null if not specified, so make sure calling host.Start does not throw.
+            var outputContext = new OutputContext(_sink, Verbosity.Debug);
+            var projectFile = new FileInfo(yamlFile);
+
+            await Assert.ThrowsAsync<CommandException>(async () => await ApplicationFactory.CreateAsync(outputContext, projectFile, "foobar"));
+        }
     }
 }

test/E2ETest/ApplicationTests.cs

@@ -25,7 +25,8 @@ namespace E2ETest
 
             // Debug targets can be null if not specified, so make sure calling host.Start does not throw.
             var outputContext = new OutputContext(_sink, Verbosity.Debug);
-            var application = await ApplicationFactory.CreateAsync(outputContext, new FileInfo(yamlFile));
+            var projectFile = new FileInfo(yamlFile);
+            var application = await ApplicationFactory.CreateAsync(outputContext, projectFile);
 
             var app = application.ToHostingApplication();
             var dictionary = new Dictionary<string, string>();

test/E2ETest/TyeBuildTests.Dockerfile.cs

@@ -210,5 +210,74 @@ namespace E2ETest
                 await DockerAssert.DeleteDockerImagesAsync(output, imageName);
             }
         }
+
+        [ConditionalFact]
+        [SkipIfDockerNotRunning]
+        public async Task TyeBuild_MultipleTargetFrameworks_CliArgs()
+        {
+            var projectName = "multi-targetframeworks";
+            var environment = "production";
+            var imageName = "test/multi-targetframeworks";
+
+            await DockerAssert.DeleteDockerImagesAsync(output, imageName);
+
+            using var projectDirectory = CopyTestProjectDirectory(projectName);
+
+            var projectFile = new FileInfo(Path.Combine(projectDirectory.DirectoryPath, "tye-no-buildproperties.yaml"));
+
+            var outputContext = new OutputContext(sink, Verbosity.Debug);
+            var application = await ApplicationFactory.CreateAsync(outputContext, projectFile, "netcoreapp3.1");
+
+            application.Registry = new ContainerRegistry("test");
+
+            try
+            {
+                await BuildHost.ExecuteBuildAsync(outputContext, application, environment, interactive: false);
+
+                var publishOutput = Assert.Single(application.Services.Single().Outputs.OfType<ProjectPublishOutput>());
+                Assert.False(Directory.Exists(publishOutput.Directory.FullName), $"Directory {publishOutput.Directory.FullName} should be deleted.");
+
+                await DockerAssert.AssertImageExistsAsync(output, imageName);
+            }
+            finally
+            {
+                await DockerAssert.DeleteDockerImagesAsync(output, imageName);
+            }
+        }
+
+        [ConditionalFact]
+        [SkipIfDockerNotRunning]
+        public async Task TyeBuild_MultipleTargetFrameworks_YamlBuildProperties()
+        {
+            var projectName = "multi-targetframeworks";
+            var environment = "production";
+            var imageName = "test/multi-targetframeworks";
+
+            await DockerAssert.DeleteDockerImagesAsync(output, imageName);
+
+            using var projectDirectory = CopyTestProjectDirectory(projectName);
+
+            var projectFile = new FileInfo(Path.Combine(projectDirectory.DirectoryPath, "tye-with-netcoreapp31.yaml"));
+
+            var outputContext = new OutputContext(sink, Verbosity.Debug);
+            var application = await ApplicationFactory.CreateAsync(outputContext, projectFile, "netcoreapp3.1");
+
+            application.Registry = new ContainerRegistry("test");
+
+            try
+            {
+                await BuildHost.ExecuteBuildAsync(outputContext, application, environment, interactive: false);
+
+                var publishOutput = Assert.Single(application.Services.Single().Outputs.OfType<ProjectPublishOutput>());
+                Assert.False(Directory.Exists(publishOutput.Directory.FullName), $"Directory {publishOutput.Directory.FullName} should be deleted.");
+
+                await DockerAssert.AssertImageExistsAsync(output, imageName);
+            }
+            finally
+            {
+                await DockerAssert.DeleteDockerImagesAsync(output, imageName);
+            }
+        }
+
     }
 }

test/E2ETest/TyeRunTests.cs

@@ -823,12 +823,14 @@ services:
   repository: https://github.com/jkotalik/TyeMultiRepoVoting
 - name: results
   repository: https://github.com/jkotalik/TyeMultiRepoResults";
+
             var yamlFile = Path.Combine(projectDirectory.DirectoryPath, "tye.yaml");
+            var projectFile = new FileInfo(yamlFile);
             await File.WriteAllTextAsync(yamlFile, content);
 
             // Debug targets can be null if not specified, so make sure calling host.Start does not throw.
             var outputContext = new OutputContext(_sink, Verbosity.Debug);
-            var application = await ApplicationFactory.CreateAsync(outputContext, new FileInfo(yamlFile));
+            var application = await ApplicationFactory.CreateAsync(outputContext, projectFile);
 
             var handler = new HttpClientHandler
             {
@@ -908,10 +910,12 @@ services:
 - name: frontend
   project: frontend/frontend.csproj";
 
-            var projectFile = Path.Combine(projectDirectory.DirectoryPath, "tye.yaml");
-            await File.WriteAllTextAsync(projectFile, content);
+            var yamlFile = Path.Combine(projectDirectory.DirectoryPath, "tye.yaml");
+            var projectFile = new FileInfo(yamlFile);
+            await File.WriteAllTextAsync(yamlFile, content);
+
             var outputContext = new OutputContext(_sink, Verbosity.Debug);
-            var application = await ApplicationFactory.CreateAsync(outputContext, new FileInfo(projectFile));
+            var application = await ApplicationFactory.CreateAsync(outputContext, projectFile);
 
             var handler = new HttpClientHandler
             {
@@ -937,6 +941,99 @@ services:
             });
         }
 
+        [ConditionalFact]
+        [SkipIfDockerNotRunning]
+        public async Task RunExplicitYamlMultipleTargetFrameworksTest()
+        {
+            using var projectDirectory = CopyTestProjectDirectory("multi-targetframeworks");
+
+            var projectFile = new FileInfo(Path.Combine(projectDirectory.DirectoryPath, "tye-with-netcoreapp31.yaml"));
+            var outputContext = new OutputContext(_sink, Verbosity.Debug);
+            var application = await ApplicationFactory.CreateAsync(outputContext, projectFile);
+
+            var handler = new HttpClientHandler
+            {
+                ServerCertificateCustomValidationCallback = (a, b, c, d) => true,
+                AllowAutoRedirect = false
+            };
+
+            var client = new HttpClient(new RetryHandler(handler));
+
+            await RunHostingApplication(application, new HostOptions(), async (app, uri) =>
+            {
+                // make sure it is running
+                var backendUri = await GetServiceUrl(client, uri, "multi-targetframeworks");
+
+                var backendResponse = await client.GetAsync(backendUri);
+                Assert.True(backendResponse.IsSuccessStatusCode);
+
+                var responseContent = await backendResponse.Content.ReadAsStringAsync();
+                Assert.Contains(".NET Core 3.1", responseContent);
+            });
+        }
+
+        [ConditionalFact]
+        [SkipIfDockerNotRunning]
+        public async Task RunWithArgsMultipleTargetFrameworksTest()
+        {
+            using var projectDirectory = CopyTestProjectDirectory("multi-targetframeworks");
+
+            var projectFile = new FileInfo(Path.Combine(projectDirectory.DirectoryPath, "tye-no-buildproperties.yaml"));
+            var outputContext = new OutputContext(_sink, Verbosity.Debug);
+            var application = await ApplicationFactory.CreateAsync(outputContext, projectFile, "netcoreapp3.1");
+
+            var handler = new HttpClientHandler
+            {
+                ServerCertificateCustomValidationCallback = (a, b, c, d) => true,
+                AllowAutoRedirect = false
+            };
+
+            var client = new HttpClient(new RetryHandler(handler));
+
+            await RunHostingApplication(application, new HostOptions(), async (app, uri) =>
+            {
+                // make sure it is running
+                var backendUri = await GetServiceUrl(client, uri, "multi-targetframeworks");
+
+                var backendResponse = await client.GetAsync(backendUri);
+                Assert.True(backendResponse.IsSuccessStatusCode);
+
+                var responseContent = await backendResponse.Content.ReadAsStringAsync();
+                Assert.Contains(".NET Core 3.1", responseContent);
+            });
+        }
+
+        [ConditionalFact]
+        [SkipIfDockerNotRunning]
+        public async Task RunCliArgOverrideYamlMultipleTargetFrameworksTest()
+        {
+            using var projectDirectory = CopyTestProjectDirectory("multi-targetframeworks");
+
+            var projectFile = new FileInfo(Path.Combine(projectDirectory.DirectoryPath, "tye-with-netcoreapp21.yaml"));
+            var outputContext = new OutputContext(_sink, Verbosity.Debug);
+            var application = await ApplicationFactory.CreateAsync(outputContext, projectFile, "netcoreapp3.1");
+
+            var handler = new HttpClientHandler
+            {
+                ServerCertificateCustomValidationCallback = (a, b, c, d) => true,
+                AllowAutoRedirect = false
+            };
+
+            var client = new HttpClient(new RetryHandler(handler));
+
+            await RunHostingApplication(application, new HostOptions(), async (app, uri) =>
+            {
+                // make sure it is running
+                var backendUri = await GetServiceUrl(client, uri, "multi-targetframeworks");
+
+                var backendResponse = await client.GetAsync(backendUri);
+                Assert.True(backendResponse.IsSuccessStatusCode);
+
+                var responseContent = await backendResponse.Content.ReadAsStringAsync();
+                Assert.Contains(".NET Core 3.1", responseContent);
+            });
+        }
+
         private async Task<string> GetServiceUrl(HttpClient client, Uri uri, string serviceName)
         {
             var serviceResult = await client.GetStringAsync($"{uri}api/v1/services/{serviceName}");

test/E2ETest/testassets/projects/multi-targetframeworks/multi-targetframeworks.sln

@@ -0,0 +1,34 @@
+
+Microsoft Visual Studio Solution File, Format Version 12.00
+# Visual Studio 15
+VisualStudioVersion = 15.0.26124.0
+MinimumVisualStudioVersion = 15.0.26124.0
+Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "multi-targetframeworks", "multi-targetframeworks\multi-targetframeworks.csproj", "{CA427ACE-098F-4883-8A91-02F766FC2D46}"
+EndProject
+Global
+	GlobalSection(SolutionConfigurationPlatforms) = preSolution
+		Debug|Any CPU = Debug|Any CPU
+		Debug|x64 = Debug|x64
+		Debug|x86 = Debug|x86
+		Release|Any CPU = Release|Any CPU
+		Release|x64 = Release|x64
+		Release|x86 = Release|x86
+	EndGlobalSection
+	GlobalSection(SolutionProperties) = preSolution
+		HideSolutionNode = FALSE
+	EndGlobalSection
+	GlobalSection(ProjectConfigurationPlatforms) = postSolution
+		{CA427ACE-098F-4883-8A91-02F766FC2D46}.Debug|Any CPU.ActiveCfg = Debug|Any CPU
+		{CA427ACE-098F-4883-8A91-02F766FC2D46}.Debug|Any CPU.Build.0 = Debug|Any CPU
+		{CA427ACE-098F-4883-8A91-02F766FC2D46}.Debug|x64.ActiveCfg = Debug|Any CPU
+		{CA427ACE-098F-4883-8A91-02F766FC2D46}.Debug|x64.Build.0 = Debug|Any CPU
+		{CA427ACE-098F-4883-8A91-02F766FC2D46}.Debug|x86.ActiveCfg = Debug|Any CPU
+		{CA427ACE-098F-4883-8A91-02F766FC2D46}.Debug|x86.Build.0 = Debug|Any CPU
+		{CA427ACE-098F-4883-8A91-02F766FC2D46}.Release|Any CPU.ActiveCfg = Release|Any CPU
+		{CA427ACE-098F-4883-8A91-02F766FC2D46}.Release|Any CPU.Build.0 = Release|Any CPU
+		{CA427ACE-098F-4883-8A91-02F766FC2D46}.Release|x64.ActiveCfg = Release|Any CPU
+		{CA427ACE-098F-4883-8A91-02F766FC2D46}.Release|x64.Build.0 = Release|Any CPU
+		{CA427ACE-098F-4883-8A91-02F766FC2D46}.Release|x86.ActiveCfg = Release|Any CPU
+		{CA427ACE-098F-4883-8A91-02F766FC2D46}.Release|x86.Build.0 = Release|Any CPU
+	EndGlobalSection
+EndGlobal

test/E2ETest/testassets/projects/multi-targetframeworks/multi-targetframeworks/Program.cs

@@ -0,0 +1,35 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using Microsoft.AspNetCore.Hosting;
+using Microsoft.Extensions.Hosting;
+
+#if NETCOREAPP3_1
+#else
+using Microsoft.AspNetCore;
+#endif
+
+namespace MultiTargetFrameworks
+{
+    public class Program
+    {
+        public static void Main(string[] args)
+        {
+            CreateHostBuilder(args).Build().Run();
+        }
+
+#if NETCOREAPP3_1
+        public static IHostBuilder CreateHostBuilder(string[] args) =>
+            Host.CreateDefaultBuilder(args)
+                .ConfigureWebHostDefaults(web =>
+                {
+                    web.UseStartup<Startup>();
+                });
+#else
+        public static IWebHostBuilder CreateHostBuilder(string[] args) =>
+            WebHost.CreateDefaultBuilder(args)
+                .UseStartup<Startup>();
+#endif
+    }
+}

test/E2ETest/testassets/projects/multi-targetframeworks/multi-targetframeworks/Properties/launchSettings.json

@@ -0,0 +1,27 @@
+{
+  "iisSettings": {
+    "windowsAuthentication": false,
+    "anonymousAuthentication": true,
+    "iisExpress": {
+      "applicationUrl": "http://localhost:5000",
+      "sslPort": 5001
+    }
+  },
+  "profiles": {
+    "IIS Express": {
+      "commandName": "IISExpress",
+      "launchBrowser": true,
+      "environmentVariables": {
+        "ASPNETCORE_ENVIRONMENT": "Development"
+      }
+    },
+    "multi-targetframeworks": {
+      "commandName": "Project",
+      "launchBrowser": true,
+      "applicationUrl": "https://localhost:5001;http://localhost:5000",
+      "environmentVariables": {
+        "ASPNETCORE_ENVIRONMENT": "Development"
+      }
+    }
+  }
+}

test/E2ETest/testassets/projects/multi-targetframeworks/multi-targetframeworks/Startup.cs

@@ -0,0 +1,40 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using Microsoft.AspNetCore.Builder;
+using Microsoft.Extensions.Configuration;
+using Microsoft.Extensions.DependencyInjection;
+using Microsoft.AspNetCore.Http;
+using System.Reflection;
+using System.Runtime.Versioning;
+
+namespace MultiTargetFrameworks
+{
+    public class Startup
+    {
+        public Startup(IConfiguration configuration)
+        {
+            Configuration = configuration;
+        }
+
+        public IConfiguration Configuration { get; }
+
+        public void ConfigureServices(IServiceCollection services)
+        {
+        }
+
+        public void Configure(IApplicationBuilder app)
+        {
+            app.Use(async (httpContext, next) =>
+            {
+#if NETCOREAPP3_1
+                await httpContext.Response.WriteAsync(System.Runtime.InteropServices.RuntimeInformation.FrameworkDescription);
+#else
+                var framework = Assembly.GetEntryAssembly()?.GetCustomAttribute<TargetFrameworkAttribute>()?.FrameworkName;
+                await httpContext.Response.WriteAsync(framework);
+#endif
+            });
+        }
+    }
+}

test/E2ETest/testassets/projects/multi-targetframeworks/multi-targetframeworks/appsettings.Development.json

@@ -0,0 +1,9 @@
+{
+  "Logging": {
+    "LogLevel": {
+      "Default": "Information",
+      "Microsoft": "Warning",
+      "Microsoft.Hosting.Lifetime": "Information"
+    }
+  }
+}

test/E2ETest/testassets/projects/multi-targetframeworks/multi-targetframeworks/appsettings.json

@@ -0,0 +1,10 @@
+{
+  "Logging": {
+    "LogLevel": {
+      "Default": "Information",
+      "Microsoft": "Warning",
+      "Microsoft.Hosting.Lifetime": "Information"
+    }
+  },
+  "AllowedHosts": "*"
+}

test/E2ETest/testassets/projects/multi-targetframeworks/multi-targetframeworks/multi-targetframeworks.csproj

@@ -0,0 +1,12 @@
+<Project Sdk="Microsoft.NET.Sdk.Web">
+
+  <PropertyGroup>
+    <TargetFrameworks>netcoreapp3.1;netcoreapp2.1</TargetFrameworks>
+    <RootNamespace>MultiTargetFrameworks</RootNamespace>
+  </PropertyGroup>
+
+  <ItemGroup Condition=" '$(TargetFramework)' == 'netcoreapp2.1'">
+    <PackageReference Include="Microsoft.AspNetCore.App" />
+  </ItemGroup>
+
+</Project>

test/E2ETest/testassets/projects/multi-targetframeworks/tye-no-buildproperties.yaml

@@ -0,0 +1,8 @@
+# tye application configuration file
+# read all about it at https://github.com/dotnet/tye
+name: multi-targetframeworks
+services:
+- name: multi-targetframeworks
+  project: multi-targetframeworks/multi-targetframeworks.csproj
+  bindings:
+  - port: 7000

test/E2ETest/testassets/projects/multi-targetframeworks/tye-with-netcoreapp21.yaml

@@ -0,0 +1,9 @@
+# tye application configuration file
+# read all about it at https://github.com/dotnet/tye
+name: multi-targetframeworks
+services:
+- name: multi-targetframeworks
+  project: multi-targetframeworks/multi-targetframeworks.csproj
+  buildProperties:
+    - name: TargetFramework
+      value: netcoreapp2.1

test/E2ETest/testassets/projects/multi-targetframeworks/tye-with-netcoreapp31.yaml

@@ -0,0 +1,9 @@
+# tye application configuration file
+# read all about it at https://github.com/dotnet/tye
+name: multi-targetframeworks
+services:
+- name: multi-targetframeworks
+  project: multi-targetframeworks/multi-targetframeworks.csproj
+  buildProperties:
+    - name: TargetFramework
+      value: netcoreapp3.1