# Fan-out/Fan-in

This tutorial demonstrates how to author a workflow where multiple independent tasks can be scheduled and executed simultaneously. The workflow can either wait until all tasks are completed, or when the fastest task is completed. For more information about the fan-out/fan-in pattern see the [Dapr docs](https://docs.dapr.io/developing-applications/building-blocks/workflow/workflow-patterns/#fan-outfan-in).

## Inspect the code

Open the `FanOutFanInWorkflow.cs` file in the `tutorials/workflow/csharp/fan-out-fan-in/FanOutFanIn` folder. This file contains the definition for the workflow.

```mermaid
graph LR
   SW((Start
   Workflow))
   subgraph for each word in the input
    GWL[GetWordLength]
   end
   SHORT[Select the
   shortest word]
   ALL[Wait until all tasks
   are completed]
   EW((End
   Workflow))
   SW --> GWL
   GWL --> ALL
   ALL --> SHORT
   SHORT --> EW
```

## Run the tutorial

1. Use a terminal to navigate to the `tutorials/workflow/csharp/fan-out-fan-in` folder.
2. Build the project using the .NET CLI.

    ```bash
    dotnet build ./FanOutFanIn/
    ```

3. Use the Dapr CLI to run the Dapr Multi-App run file

    ```bash
    dapr run -f .
    ```

4. Use the POST request in the [`fanoutfanin.http`](./fanoutfanin.http) file to start the workflow.

    The input for the workflow is an array of strings:

    ```json
    [
        "which",
        "word",
        "is",
        "the",
        "shortest"
    ]
    ```

5. Use the GET request in the [`fanoutfanin.http`](./fanoutfanin.http) file to get the status of the workflow.

    The expected serialized output of the workflow is:

    ```txt
    "\"is\""
    ```

6. Stop the Dapr Multi-App run process by pressing `Ctrl+C`.