Hello World

In this topic, we'll setup a simple Console and an ASP.NET Core application that can host and execute workflows.

Console

1

Create Console App

Start by creating a new console application:

dotnet new console -n "ElsaConsole"

2

Add Packages

Navigate to your newly created project's root directory and add the following packages:

cd ElsaConsole
dotnet add package Elsa

3

Modify Program.cs

Open Program.cs and replace its contents with the following:

using Elsa.Extensions;
using Elsa.Workflows;
using Elsa.Workflows.Activities;
using Microsoft.Extensions.DependencyInjection;

// Setup service container.
var services = new ServiceCollection();

// Add Elsa services to the container.
services.AddElsa();

// Build the service container.
var serviceProvider = services.BuildServiceProvider();

// Define a simple workflow with multiple activities.
var workflow = new Sequence
{
    Activities =
    {
        new WriteLine("Hello World!"),
        new WriteLine("We can do more than a one-liner!")
    }
};

// Resolve a workflow runner to execute the workflow.
var workflowRunner = serviceProvider.GetRequiredService<IWorkflowRunner>();

// Run the workflow.
await workflowRunner.RunAsync(workflow);

This code sets up a service container and adds Elsa services to it. The serviceProvider can be used to resolve Elsa services and run workflows.

ASP.NET Core

Note: The ASP.NET Core sample below may require updates to work with the latest Elsa 3.2+/3.3 versions. For a fully working sample compatible with the current version of Elsa, please refer to the Elsa Samples repository.

1

Create the Project

Create a new empty ASP.NET app using the following command:

dotnet new web -n "ElsaWeb"

2

Add Packages

Navigate to your project's root directory and install the Elsa package:

cd ElsaWeb
dotnet add package Elsa
dotnet add package Elsa.Http

3

Modify Program.cs

Open Program.cs in your project and replace its contents with the code provided below.

Program.cs

using Elsa.Extensions;
using ElsaWeb.Workflows;

var builder = WebApplication.CreateBuilder(args);

// Add services to the container.
builder.Services.AddControllers();
builder.Services.AddElsa(elsa =>
{
    elsa.AddWorkflow<HttpHelloWorld>();
    elsa.UseHttp(http => http.ConfigureHttpOptions = options =>
    {
        options.BaseUrl = new Uri("https://localhost:5001");
        options.BasePath = "/workflows";
    });
});

var app = builder.Build();

// Configure the HTTP request pipeline.
app.UseHttpsRedirection();
app.UseAuthorization();
app.MapControllers();
app.UseWorkflows();
app.Run();

4

Add HttpHelloWorld Workflow

Create a new directory called Workflows and add a new file to it called HttpHelloWorld.cs with the following.

Workflows/HttpHelloWorld.cs

using Elsa.Http;
using Elsa.Workflows;
using Elsa.Workflows.Activities;
using Elsa.Workflows.Contracts;

namespace ElsaWeb.Workflows;

public class HttpHelloWorld : WorkflowBase
{
    protected override void Build(IWorkflowBuilder builder)
    {
        var queryStringsVariable = builder.WithVariable<IDictionary<string, object>>();
        var messageVariable = builder.WithVariable<string>();

        builder.Root = new Sequence
        {
            Activities =
            {
                new HttpEndpoint
                {
                    Path = new("/hello-world"),
                    CanStartWorkflow = true,
                    QueryStringData = new(queryStringsVariable)
                },
                new SetVariable
                {
                    Variable = messageVariable,
                    Value = new(context =>
                    {
                        var queryStrings = queryStringsVariable.Get(context)!;
                        var message = queryStrings.TryGetValue("message", out var messageValue) ? messageValue.ToString() : "Hello world of HTTP workflows!";
                        return message;
                    })
                },
                new WriteHttpResponse
                {
                    Content = new(messageVariable)
                }
            }
        };
    }
}

Summary

This document explains setting up Console and ASP.NET Core apps using Elsa workflows. For the Console app, we configured a service container, added Elsa, and ran a "Hello World" workflow. The ASP.NET Core app integrates Elsa with HTTP endpoints to process workflows. Follow the code samples for package additions and Program.cs configurations. Refer to source code links for further details.

Source Code

• Console app

• ASP.NET Core app