Use the IExternalCommand approach

Oct 13, 2025 by wbrum.org 21 views

P&ID Error in 2025: A Deep Dive into the Autodesk Revit API

Introduction

In the world of Autodesk Revit, creating accurate and reliable Process and Instrumentation Diagrams (P&IDs) is crucial for various industries, including oil and gas, chemical, and power generation. However, with the release of Revit 2025, users have encountered a peculiar issue that affects the creation of P&IDs. In this article, we will delve into the problem, explore its causes, and provide a solution to help users overcome this challenge.

The Issue: P&ID Error in 2025

The issue at hand is related to the use of the Autodesk Revit API, specifically the RevitModelingHost class. When attempting to create a P&ID using the API, users may encounter an error that prevents them from inserting detail family instances at a picked point in the active view. This error is not limited to a specific command or function but rather seems to be related to the way the API interacts with the Revit model.

The Problem: IExternalCommand vs. Toolkit.External.ExternalCommand

To better understand the issue, let's examine the two approaches used to create the demo app:

IExternalCommand: This approach involves creating a custom command that inserts a detail family instance at a picked point in the active view. The code is placed inside an IExternalCommand interface, which is a standard way of creating custom commands in Revit.
Toolkit.External.ExternalCommand: This approach uses the Autodesk Revit API Toolkit to create an external command. The code is placed inside a Toolkit.External.ExternalCommand class, which is a part of the API Toolkit.

The issue arises when using the second approach, where the error is reported on the Autodesk forums. This suggests that the problem may be related to the way the API Toolkit interacts with the Revit model.

The Solution: A Demo App to the Rescue

To help users understand and reproduce the issue, a demo app has been created and published on GitHub. The app, titled "PaIDErrorDemo," provides a simple example of the problem and can be used as a starting point for further investigation.

Is This a Bug in the Toolkit or a Code Issue?

The question remains: is this a bug in the Autodesk Revit API Toolkit or a code issue? To determine the cause of the problem, we need to examine the code and the API Toolkit's behavior.

Code Analysis

Let's take a closer look at the code used in the demo app. The code is straightforward and inserts a detail family instance at a picked point in the active view. However, when using the Toolkit.External.ExternalCommand approach, the error is reported.

using Autodesk.Revit.UI;
using Autodesk.Revit.DB;
using Autodesk.Revit.Attributes;

namespace PaIDErrorDemo
{
    [Transaction(TransactionMode.Manual)]
    public class ExternalCommand : IExternalCommand
    {
        public Result Execute(ExternalCommandData commandData, ref string message, ElementSet elements)
        {
            // Get the active view
            View activeView = commandData.Application.ActiveView;

            // Get the picked point
            XYZ pickedPoint = commandData.Application.ActiveUIDocument.Selection.PickPoint();

            // Create a new detail family instance
            FamilyInstance detailFamilyInstance = activeView.CreateNewFamilyInstance(pickedPoint, "Detail Family", "Detail Family Type");

            return Result.Succeeded;
        }
    }
}

API Toolkit Analysis

The API Toolkit is a powerful tool that provides a set of pre-built classes and methods to simplify the development of custom Revit commands. However, in this case, the issue may be related to the way the API Toolkit interacts with the Revit model.

Conclusion

In conclusion, the P&ID error in 2025 is a complex issue that requires a deep understanding of the Autodesk Revit API and the API Toolkit. While the demo app provides a simple example of the problem, further investigation is needed to determine the cause of the issue. Is this a bug in the toolkit or a code issue? The answer lies in the code and the API Toolkit's behavior.

Recommendations

To overcome this challenge, we recommend the following:

Use the IExternalCommand approach: If possible, use the standard IExternalCommand approach to create custom commands in Revit.
Use the demo app as a starting point: The demo app provides a simple example of the problem and can be used as a starting point for further investigation.
Investigate the API Toolkit's behavior: Examine the API Toolkit's behavior and interaction with the Revit model to determine the cause of the issue.
Report the issue: If you encounter this issue, report it to the Autodesk forums or support team to help identify the cause and provide a solution.

By following these recommendations, users can overcome the P&ID error in 2025 and create accurate and reliable Process and Instrumentation Diagrams (P&IDs) in Autodesk Revit.
P&ID Error in 2025: A Q&A Article

Introduction

In our previous article, we delved into the issue of the P&ID error in 2025, a complex problem that affects the creation of Process and Instrumentation Diagrams (P&IDs) in Autodesk Revit. In this article, we will provide a Q&A section to help users better understand the issue and its causes.

Q&A

Q: What is the P&ID error in 2025?

A: The P&ID error in 2025 is a complex issue that affects the creation of Process and Instrumentation Diagrams (P&IDs) in Autodesk Revit. It is related to the use of the Autodesk Revit API, specifically the RevitModelingHost class.

Q: What are the symptoms of the P&ID error in 2025?

A: The symptoms of the P&ID error in 2025 include an error that prevents users from inserting detail family instances at a picked point in the active view. This error is not limited to a specific command or function but rather seems to be related to the way the API interacts with the Revit model.

Q: Is this a bug in the Autodesk Revit API Toolkit or a code issue?

A: The cause of the issue is still unknown, but it is believed to be related to the way the API Toolkit interacts with the Revit model. Further investigation is needed to determine the cause of the issue.

Q: What is the difference between IExternalCommand and Toolkit.External.ExternalCommand?

A: IExternalCommand is a standard way of creating custom commands in Revit, while Toolkit.External.ExternalCommand is a part of the Autodesk Revit API Toolkit. The issue arises when using the second approach, where the error is reported.

Q: Can I use the demo app to reproduce the issue?

A: Yes, the demo app provides a simple example of the problem and can be used as a starting point for further investigation.

Q: What are the recommendations for overcoming this challenge?

A: To overcome this challenge, we recommend using the IExternalCommand approach, using the demo app as a starting point, investigating the API Toolkit's behavior, and reporting the issue to the Autodesk forums or support team.

Q: Is this issue specific to Revit 2025?

A: The issue is believed to be specific to Revit 2025, but further investigation is needed to confirm this.

Q: Can I get help from Autodesk support?

A: Yes, you can report the issue to the Autodesk forums or support team for further assistance.

Conclusion

In conclusion, the P&ID error in 2025 is a complex issue that requires a deep understanding of the Autodesk Revit API and the API Toolkit. By following the recommendations and using the demo app as a starting point, users can overcome this challenge and create accurate and reliable Process and Instrumentation Diagrams (P&IDs) in Autodesk Revit.

Additional Resources

Autodesk Revit API Documentation: https://knowledge.autodesk.com/support/revit
Autodesk Revit API Toolkit Documentation: https://knowledge.autodesk.com/support/revit
Demo App: https://github.com/russgreen/PaIDErrorDemo

Contact Us

If you have any further questions or need additional assistance, please don't hesitate to contact us. We are here to help you overcome this challenge and create accurate and reliable Process and Instrumentation Diagrams (P&IDs) in Autodesk Revit.