---
title: "SDK: Flow Steps (Basic)"
slug: "flow-steps-simple"
description: "Learn how to create custom Flow Steps in Visual Studio by referencing Decisions, using a zip code validation example."
tags: ["Flow Step", "SDK Basic", "SDK"]
updated: 2026-04-27T20:46:52Z
published: 2026-04-28T14:12:58Z
canonical: "documentation.decisions.com/flow-steps-simple"
---

> ## Documentation Index
> Fetch the complete documentation index at: https://documentation.decisions.com/llms.txt
> Use this file to discover all available pages before exploring further.

# SDK: Flow Steps (Basic)

## Overview

Developers can easily create custom Flow and Rule steps by methods in a **Class Library (.NET Core) project**. This article will show users how to accomplish this. For more examples

Prerequisites

- Knowledge of the desired integrated development environment (IDE) for development
- Understanding of SDK in Decisions. To learn more, visit [SDK Overview](https://documentation.decisions.com/version-10/docs/sdk-overview) and [SDK Basics](https://documentation.decisions.com/version-10/docs/project-sdk-extensions).
- Custom steps will be located and stored at **C:\Program Files\Decisions\Decisions Server\modules\Decisions.Local\CoreServiceDlls**

---

## Basic Flow Step

The below code example will create a Flow step that checks if a string is 5 digits long. For more examples, check the [Public GitHub Repository](https://github.com/decisions-com/sdk-examples) for Decisions.

This code uses the **AutoRegisterMethodsOnClass** attribute, which will allow the code to show as a Flow step in the Steps panel. This attribute and others are further explained in the [AutoRegister Attribute Glossary](https://documentation.decisions.com/version-10/docs/autoregister-attributes) article.

```csharp

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using DecisionsFramework.Design.Flow;

namespace ShippingExtensions
{
    [AutoRegisterMethodsOnClass(true, "SDK/ZipCode")]
    public class ZipCodeManagement
    {
        public bool IsZipCodeValid(string zipCode) {
            if (zipCode.Length ==5) {
                foreach (char eachChar in zipCode.ToCharArray()) {
                    if (Char.IsDigit(eachChar) == false) {
                        return false;
                    }
                }
                return true;
            }
            return false;
        }
    }
}
```

| Code Snippet | What it does |
| --- | --- |
| using DecisionsFramework.Design.Flow | Decisions reference |
| [AutoRegisterMethodsOnClass(true, "SDK/ZipCode")] | This attribute will allow the code to show as a Flow step in the Steps panel. "SDK/ZipCode" will be the categories that this step is nested in within. |
| IsZipCodeValid(string zipCode) | This will be the name of the step and (string zipCode) will be the input. |
| return true | The output of this step |
| return false | The output of this step |

---

## Using the Method in Decisions

After writing the method to build the project, add it to Decisions by following the steps in [Software Development Kit (SDK) Overview](https://documentation.decisions.com/version-10/docs/sdk-overview).

Custom code needs to be saved here: **C:\Program Files\Decisions\Decisions Server\modules\Decisions.Local\CoreServicesDlls**

1. [Create a new Flow](/version-10/docs/create-flows).
2. In the **Steps** panel, navigate to **SDK > ZipCode.**   
![](https://cdn.document360.io/6ef8bcc1-6489-4486-9ad1-83acff7e5df0/Images/Documentation/2024-08-22_16h58_21.png)
3. Drag and drop the custom **Is Zip Code Valid** step onto the workspace.
4. This step displays as a Rule step with a True and False outcome as stated in the method written. The step also has the Zip Code input that is expecting a string.
5. Click **Unknown** and select **Constant** as the mapping type, and type in a 5-digit zip code.  
![](https://cdn.document360.io/6ef8bcc1-6489-4486-9ad1-83acff7e5df0/Images/Documentation/2024-08-22_17h00_04.png)
6. Click **Save** to save changes to the Flow.

---

## Debug

1. Click **Debug** on the top action bar. In the debugger, the Flow runs using "23322" as the input for the Rule step, and the step outputs as True.  
![](https://cdn.document360.io/6ef8bcc1-6489-4486-9ad1-83acff7e5df0/Images/Documentation/2024-08-22_17h01_00.png)

---

For further information on SDK, visit the [Decisions Forum](https://community.decisions.com/categories/SDK).