.Net: SK Process - Sample 3 Food related samples (#9087)

### Description
Adding more SK Processes samples:

- Creating SK Process Event Builder: helps link process events to Steps
internal events
- Adding samples to showcase:
    - reuse of steps]
    - use of steps specific functions
    - how to make use of step functions that output multiple events
    - use of cycles: FoodRuined -> must prepare the food from scratch

For additional details check the `GettingStartedWithProcesses/README.md`
file

### Contribution Checklist

<!-- Before submitting this PR, please make sure: -->

- [x] The code builds clean without any errors or warnings
- [x] The PR follows the [SK Contribution
Guidelines](https://github.com/microsoft/semantic-kernel/blob/main/CONTRIBUTING.md)
and the [pre-submission formatting
script](https://github.com/microsoft/semantic-kernel/blob/main/CONTRIBUTING.md#development-scripts)
raises no violations
- [x] All unit tests pass, and I have added new tests where possible
- [x] I didn't break anyone 😄

dotnet/samples/GettingStartedWithProcesses/README.md

@@ -23,6 +23,7 @@ Example|Description
 ---|---
 [Step01_Processes](https://github.com/microsoft/semantic-kernel/blob/main/dotnet/samples/GettingStartedWithProcesses/Step01/Step01_Processes.cs)|How to create a simple process with a loop and a conditional exit
 [Step02_AccountOpening](https://github.com/microsoft/semantic-kernel/blob/main/dotnet/samples/GettingStartedWithProcesses/Step02/Step02_AccountOpening.cs)|Showcasing processes cycles, fan in, fan out for opening an account.
+[Step03_FoodPreparation](https://github.com/microsoft/semantic-kernel/blob/main/dotnet/samples/GettingStartedWithProcesses/Step03/Step03_FoodPreparation.cs)|Showcasing reuse of steps, creation of processes, spawning of multiple events.
 
 ### Step01_Processes
 
@@ -66,6 +67,100 @@ flowchart LR
     Mailer -->|End of Interaction| User
 ```
 
+### Step03_FoodPreparation
+
+This tutorial contains a set of food recipes associated with the Food Preparation Processes of a restaurant.
+
+The following recipes for preparation of Order Items are defined as SK Processes:
+
+#### Product Preparation Processes
+
+##### Potato Fries Preparation Process
+
+``` mermaid
+flowchart LR
+    PreparePotatoFriesEvent([Prepare Potato <br/> Fries Event])
+    PotatoFriesReadyEvent([Potato Fries <br/> Ready Event])
+
+    GatherIngredientsStep[Gather Ingredients <br/> Step]
+    CutStep[Cut Food <br/> Step]
+    FryStep[Fry Food <br/> Step]
+
+    PreparePotatoFriesEvent --> GatherIngredientsStep -->| Slice Potatoes <br/> _Ingredients Gathered_ | CutStep --> |**Potato Sliced Ready** <br/> _Food Sliced Ready_ | FryStep --> |_Fried Food Ready_|PotatoFriesReadyEvent
+    FryStep -->|Fried Potato Ruined <br/> _Fried Food Ruined_| GatherIngredientsStep
+```
+
+##### Fried Fish Preparation Process
+
+``` mermaid
+flowchart LR
+    PrepareFriedFishEvent([Prepare Fried <br/> Fish Event])
+    FriedFishReadyEvent([Fried Fish <br/> Ready Event])
+
+    GatherIngredientsStep[Gather Ingredients <br/> Step]
+    CutStep[Cut Food <br/> Step]
+    FryStep[Fry Food <br/> Step]
+
+    PrepareFriedFishEvent --> GatherIngredientsStep -->| Chop Fish <br/> _Ingredients Gathered_ | CutStep --> |**Fish Chopped Ready** <br/> _Food Chopped Ready_| FryStep --> |_Fried Food Ready_ | FriedFishReadyEvent
+    FryStep -->|**Fried Fish Ruined** <br/> _Fried Food Ruined_| GatherIngredientsStep
+```
+
+##### Fish Sandwich Preparation Process
+
+``` mermaid
+flowchart LR
+    PrepareFishSandwichEvent([Prepare Fish <br/> Sandwich Event])
+    FishSandwichReadyEvent([Fish Sandwich <br/> Ready Event])
+
+    FriedFishStep[[Fried Fish <br/> Process Step]]
+    AddBunsStep[Add Buns <br/> Step]
+    AddSpecialSauceStep[Add Special <br/> Sauce Step]
+
+    PrepareFishSandwichEvent -->|Prepare Fried Fish| FriedFishStep -->|Fried Fish Ready| AddBunsStep --> |Buns Added  | AddSpecialSauceStep --> |Special Sauce Added | FishSandwichReadyEvent
+```
+
+##### Fish And Chips Preparation Process
+
+``` mermaid
+flowchart LR
+    PrepareFishAndChipsEvent([Prepare <br/> Fish And Chips <br/> Event])
+    FishAndChipsReadyEvent([Fish And Chips <br/> Ready Event])
+
+    FriedFishStep[[Fried Fish <br/> Process Step]]
+    PotatoFriesStep[[Potato Fries  <br/> Process Step]]
+    AddCondiments[Add Condiments <br/> Step ]
+
+    PrepareFishAndChipsEvent -->|Prepare Fried Fish| FriedFishStep --> |Fried Fish Ready| AddCondiments
+    PrepareFishAndChipsEvent -->|Prepare Potato Fries| PotatoFriesStep -->|Potato Fries Ready| AddCondiments
+    AddCondiments -->|Condiments Added| FishAndChipsReadyEvent
+```
+
+#### Single Order Preparation Process
+
+Now with the existing product preparation processes, they can be used to create an even more complex process that can decide what product order to dispatch.
+
+```mermaid
+graph TD
+    PrepareSingleOrderEvent([Prepare Single Order <br/> Event])
+    SingleOrderReadyEvent([Single Order <br/> Ready Event])
+    OrderPackedEvent([Order Packed <br/> Event])
+
+    DispatchOrderStep{{Dispatch <br/> Order Step}}
+    FriedFishStep[[Fried Fish  <br/> Process Step]]
+    PotatoFriesStep[[Potato Fries <br/> Process Step]]
+    FishSandwichStep[[Fish Sandwich <br/> Process Step]]
+    FishAndChipsStep[[Fish & Chips <br/> Process Step]]
+
+    PackFoodStep[Pack Food <br/> Step]
+
+    PrepareSingleOrderEvent -->|Order Received| DispatchOrderStep
+    DispatchOrderStep -->|Prepare Fried Fish| FriedFishStep -->|Fried Fish Ready| SingleOrderReadyEvent
+    DispatchOrderStep -->|Prepare Potato Fries| PotatoFriesStep -->|Potato Fries Ready| SingleOrderReadyEvent
+    DispatchOrderStep -->|Prepare Fish Sandwich| FishSandwichStep -->|Fish Sandwich Ready| SingleOrderReadyEvent
+    DispatchOrderStep -->|Prepare Fish & Chips| FishAndChipsStep -->|Fish & Chips Ready| SingleOrderReadyEvent
+
+    SingleOrderReadyEvent-->PackFoodStep --> OrderPackedEvent
+```
 
 ## Running Examples with Filters
 Examples may be explored and ran within _Visual Studio_ using _Test Explorer_.

dotnet/samples/GettingStartedWithProcesses/Step03/Models/FoodIngredients.cs

@@ -0,0 +1,37 @@
+// Copyright (c) Microsoft. All rights reserved.
+
+namespace Step03.Models;
+
+/// <summary>
+/// Food Ingredients used in steps such GatherIngredientStep, CutFoodStep, FryFoodStep
+/// </summary>
+public enum FoodIngredients
+{
+    Pototoes,
+    Fish,
+    Buns,
+    Sauce,
+    Condiments,
+    None
+}
+
+/// <summary>
+/// Extensions to have access to friendly string names for <see cref="FoodIngredients"/>
+/// </summary>
+public static class FoodIngredientsExtensions
+{
+    private static readonly Dictionary<FoodIngredients, string> s_foodIngredientsStrings = new()
+    {
+        { FoodIngredients.Pototoes, "Potatoes" },
+        { FoodIngredients.Fish, "Fish" },
+        { FoodIngredients.Buns, "Buns" },
+        { FoodIngredients.Sauce, "Sauce" },
+        { FoodIngredients.Condiments, "Condiments" },
+        { FoodIngredients.None, "None" }
+    };
+
+    public static string ToFriendlyString(this FoodIngredients ingredient)
+    {
+        return s_foodIngredientsStrings[ingredient];
+    }
+}

dotnet/samples/GettingStartedWithProcesses/Step03/Models/FoodOrderItem.cs

@@ -0,0 +1,33 @@
+// Copyright (c) Microsoft. All rights reserved.
+
+namespace Step03.Models;
+
+/// <summary>
+/// Food Items that can be prepared by the PrepareSingleFoodItemProcess
+/// </summary>
+public enum FoodItem
+{
+    PotatoFries,
+    FriedFish,
+    FishSandwich,
+    FishAndChips
+}
+
+/// <summary>
+/// Extensions to have access to friendly string names for <see cref="FoodItem"/>
+/// </summary>
+public static class FoodItemExtensions
+{
+    private static readonly Dictionary<FoodItem, string> s_foodItemsStrings = new()
+    {
+        { FoodItem.PotatoFries, "Potato Fries" },
+        { FoodItem.FriedFish, "Fried Fish" },
+        { FoodItem.FishSandwich, "Fish Sandwich" },
+        { FoodItem.FishAndChips, "Fish & Chips" },
+    };
+
+    public static string ToFriendlyString(this FoodItem item)
+    {
+        return s_foodItemsStrings[item];
+    }
+}

dotnet/samples/GettingStartedWithProcesses/Step03/Processes/FishAndChipsProcess.cs

@@ -0,0 +1,80 @@
+// Copyright (c) Microsoft. All rights reserved.
+
+using System.Text.Json;
+using Microsoft.SemanticKernel;
+using Step03.Models;
+using Step03.Steps;
+
+namespace Step03.Processes;
+
+/// <summary>
+/// Sample process that showcases how to create a process with a fan in/fan out behavior and use of existing processes as steps.<br/>
+/// Visual reference of this process can be found in the <see href="https://github.com/microsoft/semantic-kernel/tree/main/dotnet/samples/GettingStartedWithProcesses/README.md#Fish_And_Chips_Preparation_Process" >diagram</see>
+/// </summary>
+public static class FishAndChipsProcess
+{
+    public static class ProcessEvents
+    {
+        public const string PrepareFishAndChips = nameof(PrepareFishAndChips);
+        public const string FishAndChipsReady = nameof(FishAndChipsReady);
+    }
+
+    public static ProcessBuilder CreateProcess(string processName = "FishAndChipsProcess")
+    {
+        var processBuilder = new ProcessBuilder(processName);
+        var makeFriedFishStep = processBuilder.AddStepFromProcess(FriedFishProcess.CreateProcess());
+        var makePotatoFriesStep = processBuilder.AddStepFromProcess(PotatoFriesProcess.CreateProcess());
+        var addCondimentsStep = processBuilder.AddStepFromType<AddFishAndChipsCondimentsStep>();
+        // An additional step that is the only one that emits an public event in a process can be added to maintain event names unique
+        var externalStep = processBuilder.AddStepFromType<ExternalFishAndChipsStep>();
+
+        processBuilder
+            .OnInputEvent(ProcessEvents.PrepareFishAndChips)
+            .SendEventTo(makeFriedFishStep.WhereInputEventIs(FriedFishProcess.ProcessEvents.PrepareFriedFish));
+
+        processBuilder
+            .OnInputEvent(ProcessEvents.PrepareFishAndChips)
+            .SendEventTo(makePotatoFriesStep.WhereInputEventIs(PotatoFriesProcess.ProcessEvents.PreparePotatoFries));
+
+        makeFriedFishStep
+            .OnEvent(FriedFishProcess.ProcessEvents.FriedFishReady)
+            .SendEventTo(new ProcessFunctionTargetBuilder(addCondimentsStep, parameterName: "fishActions"));
+
+        makePotatoFriesStep
+            .OnEvent(PotatoFriesProcess.ProcessEvents.PotatoFriesReady)
+            .SendEventTo(new ProcessFunctionTargetBuilder(addCondimentsStep, parameterName: "potatoActions"));
+
+        addCondimentsStep
+            .OnEvent(AddFishAndChipsCondimentsStep.OutputEvents.CondimentsAdded)
+            .SendEventTo(new ProcessFunctionTargetBuilder(externalStep));
+
+        return processBuilder;
+    }
+
+    private sealed class AddFishAndChipsCondimentsStep : KernelProcessStep
+    {
+        public static class Functions
+        {
+            public const string AddCondiments = nameof(AddCondiments);
+        }
+
+        public static class OutputEvents
+        {
+            public const string CondimentsAdded = nameof(CondimentsAdded);
+        }
+
+        [KernelFunction(Functions.AddCondiments)]
+        public async Task AddCondimentsAsync(KernelProcessStepContext context, List<string> fishActions, List<string> potatoActions)
+        {
+            Console.WriteLine($"ADD_CONDIMENTS: Added condiments to Fish & Chips - Fish: {JsonSerializer.Serialize(fishActions)}, Potatoes: {JsonSerializer.Serialize(potatoActions)}");
+            fishActions.AddRange(potatoActions);
+            fishActions.Add(FoodIngredients.Condiments.ToFriendlyString());
+            await context.EmitEventAsync(new() { Id = OutputEvents.CondimentsAdded, Data = fishActions });
+        }
+    }
+
+    private sealed class ExternalFishAndChipsStep : ExternalStep
+    {
+        public ExternalFishAndChipsStep() : base(ProcessEvents.FishAndChipsReady) { }
+    }
+}

dotnet/samples/GettingStartedWithProcesses/Step03/Processes/FishSandwichProcess.cs

@@ -0,0 +1,95 @@
+// Copyright (c) Microsoft. All rights reserved.
+
+using Microsoft.SemanticKernel;
+using Step03.Models;
+using Step03.Steps;
+
+namespace Step03.Processes;
+
+/// <summary>
+/// Sample process that showcases how to create a process with sequential steps and use of existing processes as steps.<br/>
+/// Visual reference of this process can be found in the <see href="https://github.com/microsoft/semantic-kernel/tree/main/dotnet/samples/GettingStartedWithProcesses/README.md#Fish_Sandwich_Preparation_Process" >diagram</see>
+/// </summary>
+public static class FishSandwichProcess
+{
+    public static class ProcessEvents
+    {
+        public const string PrepareFishSandwich = nameof(PrepareFishSandwich);
+        public const string FishSandwichReady = nameof(FishSandwichReady);
+    }
+
+    public static ProcessBuilder CreateProcess(string processName = "FishSandwichProcess")
+    {
+        var processBuilder = new ProcessBuilder(processName);
+        var makeFriedFishStep = processBuilder.AddStepFromProcess(FriedFishProcess.CreateProcess());
+        var addBunsStep = processBuilder.AddStepFromType<AddBunsStep>();
+        var addSpecialSauceStep = processBuilder.AddStepFromType<AddSpecialSauceStep>();
+        // An additional step that is the only one that emits an public event in a process can be added to maintain event names unique
+        var externalStep = processBuilder.AddStepFromType<ExternalFriedFishStep>();
+
+        processBuilder
+            .OnInputEvent(ProcessEvents.PrepareFishSandwich)
+            .SendEventTo(makeFriedFishStep.WhereInputEventIs(FriedFishProcess.ProcessEvents.PrepareFriedFish));
+
+        makeFriedFishStep
+            .OnEvent(FriedFishProcess.ProcessEvents.FriedFishReady)
+            .SendEventTo(new ProcessFunctionTargetBuilder(addBunsStep));
+
+        addBunsStep
+            .OnEvent(AddBunsStep.OutputEvents.BunsAdded)
+            .SendEventTo(new ProcessFunctionTargetBuilder(addSpecialSauceStep));
+
+        addSpecialSauceStep
+            .OnEvent(AddSpecialSauceStep.OutputEvents.SpecialSauceAdded)
+            .SendEventTo(new ProcessFunctionTargetBuilder(externalStep));
+
+        return processBuilder;
+    }
+
+    private sealed class AddBunsStep : KernelProcessStep
+    {
+        public static class Functions
+        {
+            public const string AddBuns = nameof(AddBuns);
+        }
+
+        public static class OutputEvents
+        {
+            public const string BunsAdded = nameof(BunsAdded);
+        }
+
+        [KernelFunction(Functions.AddBuns)]
+        public async Task SliceFoodAsync(KernelProcessStepContext context, List<string> foodActions)
+        {
+            Console.WriteLine($"BUNS_ADDED_STEP: Buns added to ingredient {foodActions.First()}");
+            foodActions.Add(FoodIngredients.Buns.ToFriendlyString());
+            await context.EmitEventAsync(new() { Id = OutputEvents.BunsAdded, Data = foodActions });
+        }
+    }
+
+    private sealed class AddSpecialSauceStep : KernelProcessStep
+    {
+        public static class Functions
+        {
+            public const string AddSpecialSauce = nameof(AddSpecialSauce);
+        }
+
+        public static class OutputEvents
+        {
+            public const string SpecialSauceAdded = nameof(SpecialSauceAdded);
+        }
+
+        [KernelFunction(Functions.AddSpecialSauce)]
+        public async Task SliceFoodAsync(KernelProcessStepContext context, List<string> foodActions)
+        {
+            Console.WriteLine($"SPECIAL_SAUCE_ADDED: Special sauce added to ingredient {foodActions.First()}");
+            foodActions.Add(FoodIngredients.Sauce.ToFriendlyString());
+            await context.EmitEventAsync(new() { Id = OutputEvents.SpecialSauceAdded, Data = foodActions, Visibility = KernelProcessEventVisibility.Public });
+        }
+    }
+
+    private sealed class ExternalFriedFishStep : ExternalStep
+    {
+        public ExternalFriedFishStep() : base(ProcessEvents.FishSandwichReady) { }
+    }
+}