Create PrepareDinner workfow in StepWise

This post shows how to create a stepwise workflow in C# using PrepareDinner as an example. The complete code is available at PrepareDinner.cs. You can visit this blog post to learn more about StepWise.

You can try-out this workfow at the online demo by clicking the below button

Prepare dinner overview

The dinner preparation workflow consists of the following steps:

Where we can notice that some steps can be executed in parallel, such as CutVegetables() and BoilWater(), and some steps depend on the previous steps, such as CookVegetables() and CookMeat(). When all the steps are completed, the ServeDinner() step can be executed. This dependency can be automatically resolved by the StepWise engine after the prepare dinner workflow is defined.

Create a new StepWise project

To create a new StepWise project, you can use the StepWise template provided by StepWise. You can create a new StepWise project using the following command from dotnet-cli:

// install the StepWise template
dotnet new -i LittleLittleCloud.StepWise.Template

// create a new StepWise project
dotnet new stepwise-console -n PrepareDinnerProject

Define workflow

In StepWise, every workflow is represented as a basic C# class and every steps under that workflow is mapping to a public async method with Step Attribution.

Therefore, we can start by defining a PrepareDinner class with the following steps:

// file: PrepareDinner.cs
public class PrepareDinner
{
    // ...
}

Next, we can start adding the steps to the PrepareDinner class. We will add Start step first.

// file: PrepareDinner.cs
public class PrepareDinner
{
    [Step]
    public async Task<DateTime> Start()
    {
        Console.WriteLine("Start preparing dinner at " + DateTime.Now);

        return DateTime.Now;
    }
}

The Start step is a simple step that prints the current time to the console and returns the current time. This step is the first step in the workflow and does not depend on any other steps.

One thing to note is the Step attribute on the Start method. This attribute tells the StepWise engine that this method is a step in the workflow.

Next, we can add CutVegetables and BoilWaters steps to the PrepareDinner class. These steps will depend on the Start step, which is marked by the DependOn attribute.

// file: PrepareDinner.cs
public class PrepareDinner
{
    // ... previous steps

    [Step]
    [DependOn(nameof(Start))]
    public async Task<string> CutVegetables()
    {
        Console.WriteLine("Cutting vegetables...");
        await Task.Delay(2000);
        return "Vegetables are cut in 2 seconds";
    }

    [Step]
    [DependOn(nameof(Start))]
    public async Task<string> BoilWater()
    {
        Console.WriteLine("Boiling water...");
        await Task.Delay(3000);
        return "Water is boiled in 3 seconds";
    }
}

Next, we can add CookVegetables step. We want the CookVegetables step to depend on the CutVegetables step. This can be done by adding the DependOn attribute to the CookVegetables method. Other than the dependency, we also want to use the result of the CutVegetables step in the CookVegetables step. This can be done by adding the FromStep attribute to the CookVegetables method.

// file: PrepareDinner.cs
public class PrepareDinner
{
    // ... previous steps

    [Step]
    [DependOn(nameof(CutVegetables))]
    [DependOn(nameof(BoilWater))]
    public async Task<string> CookVegetables(
        [FromStep(nameof(CutVegetables)) string cutVegetablesResult)
    {
        Console.WriteLine("Cooking vegetables...");
        await Task.Delay(3000);

        var result = $"Vegetables are cooked in 3 seconds. {cutVegetablesResult}";

        return result;
    }
}

Finally, we can add the ServeDinner step to the PrepareDinner class. This step will depend on the CookVegetables and CookMeat steps. We can add the DependOn attribute to the ServeDinner method to specify the dependencies. We also want to use the results of the CookVegetables and CookMeat steps in the ServeDinner step. This can be done by adding the FromStep attribute to the ServeDinner method.

// file: PrepareDinner.cs
public class PrepareDinner
{
    // ... previous steps

    [Step]
    [DependOn(nameof(CookVegetables))]
    [DependOn(nameof(CookMeat))]
    public async Task<string> ServeDinner(
        [FromStep(nameof(CookVegetables)) string cookVegetablesResult,
        [FromStep(nameof(CookMeat)) string cookMeatResult)
    {
        Console.WriteLine("Serving dinner...");
        await Task.Delay(1000);

        var result = $"Dinner is served in 1 second. {cookVegetablesResult} {cookMeatResult}";

        return result;
    }
}

At this point, we have defined the PrepareDinner workflow with all the necessary steps. The workflow is ready to be executed.

Add PrepareDinner workflow to StepWise server

After the PrepareDinner workflow is defined, we can add it to the StepWise server using the StepWiseClient instance. This will allow the workflow to be executed in the StepWise UI.

// Program.cs
// ...configure the StepWise server
var stepWiseClient = host.Services.GetRequiredService<StepWiseClient>();
var prepareDinner = new PrepareDinner();
stepWiseClient.AddWorkflow(Workflow.CreateFromInstance(prepareDinner));

// Wait for the host to shutdown
await host.WaitForShutdownAsync();

The code above creates a StepWise server and adds the PrepareDinner workflow to the server. The server will be hosted on http://localhost:5123 by default. You can visit the URL to see the StepWise UI and execute the workflow.