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Add Mediator samples
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‎Microsoft.DurableTask.sln‎

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@@ -65,6 +65,8 @@ Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "Grpc", "src\Grpc\Grpc.cspro
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EndProject
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Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "Benchmarks", "test\Benchmarks\Benchmarks.csproj", "{82C0CD7D-2764-421A-8256-7E2304D5A6E7}"
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EndProject
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Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "Preview", "samples\Preview\Preview.csproj", "{EA7F706E-9738-4DDB-9089-F17F927E1247}"
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EndProject
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Global
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GlobalSection(SolutionConfigurationPlatforms) = preSolution
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Debug|Any CPU = Debug|Any CPU
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{82C0CD7D-2764-421A-8256-7E2304D5A6E7}.Debug|Any CPU.Build.0 = Debug|Any CPU
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{82C0CD7D-2764-421A-8256-7E2304D5A6E7}.Release|Any CPU.ActiveCfg = Release|Any CPU
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{82C0CD7D-2764-421A-8256-7E2304D5A6E7}.Release|Any CPU.Build.0 = Release|Any CPU
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{EA7F706E-9738-4DDB-9089-F17F927E1247}.Debug|Any CPU.ActiveCfg = Debug|Any CPU
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{EA7F706E-9738-4DDB-9089-F17F927E1247}.Debug|Any CPU.Build.0 = Debug|Any CPU
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{EA7F706E-9738-4DDB-9089-F17F927E1247}.Release|Any CPU.ActiveCfg = Release|Any CPU
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{EA7F706E-9738-4DDB-9089-F17F927E1247}.Release|Any CPU.Build.0 = Release|Any CPU
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EndGlobalSection
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GlobalSection(SolutionProperties) = preSolution
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HideSolutionNode = FALSE
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{93E3B973-0FC4-4241-B7BB-064FB538FB50} = {5AD837BC-78F3-4543-8AA3-DF74D0DF94C0}
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{44AD321D-96D4-481E-BD41-D0B12A619833} = {8AFC9781-F6F1-4696-BB4A-9ED7CA9D612B}
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{82C0CD7D-2764-421A-8256-7E2304D5A6E7} = {E5637F81-2FB9-4CD7-900D-455363B142A7}
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{EA7F706E-9738-4DDB-9089-F17F927E1247} = {EFF7632B-821E-4CFC-B4A0-ED4B24296B17}
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EndGlobalSection
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GlobalSection(ExtensibilityGlobals) = postSolution
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SolutionGuid = {AB41CB55-35EA-4986-A522-387AB3402E71}

‎samples/Preview/MediatorPattern/Mediator1/ExistingTypesOrchestration.cs‎

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// Copyright (c) Microsoft Corporation.
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// Licensed under the MIT License.
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using McMaster.Extensions.CommandLineUtils;
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using Microsoft.DurableTask;
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using Microsoft.Extensions.Logging;
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namespace Preview.MediatorPattern.ExistingTypes;
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/**
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* This sample shows mediator-pattern orchestrations and activities using existing types as their inputs. In this mode,
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* the request object provides a distinct separate object as the input to the task. The below code has no real purpose
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* nor demonstrates good ways to organize orchestrations or activities. The purpose is to demonstrate how the static
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* 'CreateRequest' method way of using the mediator pattern.
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*
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* This is just one such way to leverage the mediator-pattern. Ultimately all the request object is all that is needed,
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* how it is created is flexible.
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*/
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public class MediatorOrchestrator1 : TaskOrchestrator<MyInput> // Single generic means it has no output. Only input.
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{
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public static IOrchestrationRequest CreateRequest(string propA, string propB)
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=> OrchestrationRequest.Create(nameof(MediatorOrchestrator1), new MyInput(propA, propB));
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public override async Task RunAsync(TaskOrchestrationContext context, MyInput input)
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{
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string output = await context.RunAsync(MediatorSubOrchestrator1.CreateRequest(input.PropA));
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await context.RunAsync(WriteConsoleActivity1.CreateRequest(output));
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output = await context.RunAsync(ExpandActivity1.CreateRequest(input.PropB));
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await context.RunAsync(WriteConsoleActivity1.CreateRequest(output));
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}
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}
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public class MediatorSubOrchestrator1 : TaskOrchestrator<string, string>
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{
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public static IOrchestrationRequest<string> CreateRequest(string input)
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=> OrchestrationRequest.Create<string>(nameof(MediatorSubOrchestrator1), input);
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public override Task<string> RunAsync(TaskOrchestrationContext context, string input)
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{
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// Orchestrations create replay-safe loggers off the
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ILogger logger = context.CreateReplaySafeLogger<MediatorSubOrchestrator1>();
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logger.LogDebug("In MySubOrchestrator");
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return context.RunAsync(ExpandActivity1.CreateRequest($"{nameof(MediatorSubOrchestrator1)}: {input}"));
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}
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}
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public class WriteConsoleActivity1 : TaskActivity<string> // Single generic means it has no output. Only input.
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{
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readonly IConsole console;
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public WriteConsoleActivity1(IConsole console) // Dependency injection example.
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{
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this.console = console;
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}
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public static IActivityRequest CreateRequest(string input)
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=> ActivityRequest.Create(nameof(WriteConsoleActivity1), input);
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public override Task RunAsync(TaskActivityContext context, string input)
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{
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this.console.WriteLine(input);
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return Task.CompletedTask;
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}
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}
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public class ExpandActivity1 : TaskActivity<string, string>
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{
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readonly ILogger logger;
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public ExpandActivity1(ILogger<ExpandActivity1> logger) // Activities get logger from DI.
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{
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this.logger = logger;
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}
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public static IActivityRequest<string> CreateRequest(string input)
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=> ActivityRequest.Create<string>(nameof(ExpandActivity1), input);
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public override Task<string> RunAsync(TaskActivityContext context, string input)
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{
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this.logger.LogDebug("In ExpandActivity");
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return Task.FromResult($"Input received: {input}");
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}
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}
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public record MyInput(string PropA, string PropB);

‎samples/Preview/MediatorPattern/Mediator1/Mediator1Command.cs‎

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// Copyright (c) Microsoft Corporation.
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// Licensed under the MIT License.
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using McMaster.Extensions.CommandLineUtils;
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using Microsoft.DurableTask;
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using Preview.MediatorPattern.ExistingTypes;
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namespace Preview.MediatorPattern;
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[Command(Description = "Runs the first mediator sample")]
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public class Mediator1Command : SampleCommandBase
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{
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public static void Register(DurableTaskRegistry tasks)
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{
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tasks.AddActivity<ExpandActivity1>();
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tasks.AddActivity<WriteConsoleActivity1>();
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tasks.AddOrchestrator<MediatorOrchestrator1>();
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tasks.AddOrchestrator<MediatorSubOrchestrator1>();
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}
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protected override IBaseOrchestrationRequest GetRequest()
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{
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return MediatorOrchestrator1.CreateRequest("PropInputA", "PropInputB");
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}
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}
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‎samples/Preview/MediatorPattern/Mediator2/Mediator2Command.cs‎

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// Copyright (c) Microsoft Corporation.
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// Licensed under the MIT License.
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using McMaster.Extensions.CommandLineUtils;
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using Microsoft.DurableTask;
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using Preview.MediatorPattern.NewTypes;
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namespace Preview.MediatorPattern;
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[Command(Description = "Runs the second mediator sample")]
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public class Mediator2Command : SampleCommandBase
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{
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public static void Register(DurableTaskRegistry tasks)
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{
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tasks.AddActivity<ExpandActivity2>();
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tasks.AddActivity<WriteConsoleActivity2>();
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tasks.AddOrchestrator<MediatorOrchestrator2>();
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tasks.AddOrchestrator<MediatorSubOrchestrator2>();
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}
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protected override IBaseOrchestrationRequest GetRequest()
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{
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return new MediatorOrchestratorRequest("PropA", "PropB");
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}
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}
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‎samples/Preview/MediatorPattern/Mediator2/NewTypesOrchestration.cs‎

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// Copyright (c) Microsoft Corporation.
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// Licensed under the MIT License.
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using McMaster.Extensions.CommandLineUtils;
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using Microsoft.DurableTask;
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using Microsoft.Extensions.Logging;
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namespace Preview.MediatorPattern.NewTypes;
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/**
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* This sample shows mediator-pattern orchestrations and activities using newly defined request types as their input. In
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* this mode, the request object is the input to the task itself. The below code has no real purpose nor demonstrates
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* good ways to organize orchestrations or activities. The purpose is to demonstrate how request objects can be defined
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* manually and provided directly to RunAsync method.
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*
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* This is just one such way to leverage the mediator-pattern. Ultimately all the request object is all that is needed,
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* how it is created is flexible.
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*/
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public record MediatorOrchestratorRequest(string PropA, string PropB) : IOrchestrationRequest
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{
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public TaskName GetTaskName() => nameof(MediatorOrchestrator2);
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}
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public class MediatorOrchestrator2 : TaskOrchestrator<MediatorOrchestratorRequest> // Single generic means it has no output. Only input.
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{
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public override async Task RunAsync(TaskOrchestrationContext context, MediatorOrchestratorRequest input)
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{
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string output = await context.RunAsync(new MediatorSubOrchestratorRequest(input.PropA));
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await context.RunAsync(new WriteConsoleActivityRequest(output));
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}
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}
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public record MediatorSubOrchestratorRequest(string Value) : IOrchestrationRequest<string>
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{
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public TaskName GetTaskName() => nameof(MediatorSubOrchestrator2);
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}
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public class MediatorSubOrchestrator2 : TaskOrchestrator<MediatorSubOrchestratorRequest, string>
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{
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public override Task<string> RunAsync(TaskOrchestrationContext context, MediatorSubOrchestratorRequest input)
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{
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// Orchestrations create replay-safe loggers off the
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ILogger logger = context.CreateReplaySafeLogger<MediatorSubOrchestrator2>();
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logger.LogDebug("In MySubOrchestrator");
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return context.RunAsync(new ExpandActivityRequest($"{nameof(MediatorSubOrchestrator2)}: {input.Value}"));
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}
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}
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public record WriteConsoleActivityRequest(string Value) : IActivityRequest<string>
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{
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public TaskName GetTaskName() => nameof(WriteConsoleActivity2);
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}
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public class WriteConsoleActivity2 : TaskActivity<WriteConsoleActivityRequest> // Single generic means it has no output. Only input.
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{
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readonly IConsole console;
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public WriteConsoleActivity2(IConsole console) // Dependency injection example.
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{
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this.console = console;
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}
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public override Task RunAsync(TaskActivityContext context, WriteConsoleActivityRequest input)
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{
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this.console.WriteLine(input.Value);
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return Task.CompletedTask;
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}
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}
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public record ExpandActivityRequest(string Value) : IActivityRequest<string>
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{
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public TaskName GetTaskName() => nameof(ExpandActivity2);
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}
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public class ExpandActivity2 : TaskActivity<ExpandActivityRequest, string>
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{
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readonly ILogger logger;
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public ExpandActivity2(ILogger<ExpandActivity2> logger) // Activities get logger from DI.
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{
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this.logger = logger;
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}
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public override Task<string> RunAsync(TaskActivityContext context, ExpandActivityRequest input)
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{
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this.logger.LogDebug("In ExpandActivity");
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return Task.FromResult($"Input received: {input.Value}");
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}
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}

‎samples/Preview/MediatorPattern/README.md‎

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# Mediator Pattern
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## Running this sample
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First sample:
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``` cli
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dotnet run Preview.csproj -- mediator1
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```
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Second sample:
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``` cli
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dotnet run Preview.csproj -- mediator2
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```
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**NOTE**: see [dotnet run](https://learn.microsoft.com/dotnet/core/tools/dotnet-run). The `--` with a space following it is important.
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## What is the mediator pattern?
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> In software engineering, the mediator pattern defines an object that encapsulates how a set of objects interact. This pattern is considered to be a behavioral pattern due to the way it can alter the program's running behavior.
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>
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> -- [wikipedia](https://en.wikipedia.org/wiki/Mediator_pattern)
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Specifically to Durable Task, this means using objects to assist with enqueueing of orchestrations, sub-orchestrations, and activities. These objects handle all of the following:
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1. Defining which `TaskOrchestrator` or `TaskActivity` to run.
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2. Providing the input for the task to be ran.
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3. Defining the output type of the task.
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The end result is the ability to invoke orchestrations and activities in a type-safe manner.
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## What does it look like?
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Instead of supplying the name, input, and return type of an orchestration or activity separately, instead a 'request' object is used to do all of these at once.
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Example: enqueueing an activity.
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Raw API:
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``` CSharp
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string result = await context.RunActivityAsync<string>(nameof(MyActivity), input);
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```
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Explicit extension method [1]:
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``` csharp
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string result = await context.RunMyActivityAsync(input);
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```
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Mediator
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``` csharp
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string result = await context.RunAsync(MyActivity.CreateRequest(input));
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// OR - it is up to individual developers which style they prefer. Can also be mixed and matched as seen fit.
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string result = await context.RunAsync(new MyActivityRequest(input));
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```
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[1] - while the extension method is concise, having many extension methods off the same type can make intellisense a bit unwieldy.

‎samples/Preview/Preview.csproj‎

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<Project Sdk="Microsoft.NET.Sdk">
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<PropertyGroup>
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<OutputType>Exe</OutputType>
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<TargetFramework>net6.0</TargetFramework>
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<Nullable>enable</Nullable>
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</PropertyGroup>
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<ItemGroup>
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<PackageReference Include="Microsoft.DurableTask.Sidecar" Version="0.3.0" />
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<PackageReference Include="Microsoft.Extensions.Hosting" Version="6.0.0" />
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</ItemGroup>
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<ItemGroup>
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<ProjectReference Include="$(SrcRoot)Client/Grpc/Client.Grpc.csproj" />
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<ProjectReference Include="$(SrcRoot)Worker/Grpc/Worker.Grpc.csproj" />
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</ItemGroup>
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</Project>

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