DA4R中能否使用外部IFC导出器？如何替换内置IFC版本？

1. Can I use an external IFC exporter in DA4R? #

Absolutely, you can use an external IFC exporter in Design Automation for Revit (DA4R), but there are a few critical things to nail down:

• Bundle all dependencies: DA4R runs in a sandboxed environment, so you need to package every DLL and supporting file the external exporter requires into your activity package. Missing even one dependency will crash your job.
• Match Revit versions: Make sure the external exporter is built for the exact Revit version your DA4R activity uses. Mismatched versions will cause assembly loading failures or API conflicts.
• Headless compatibility: Confirm the exporter has no UI dependencies (like pop-up dialogs). DA4R operates without a graphical interface, so any UI-reliant code will break your workflow.

2. Can I override the built-in Revit IFC library with the SourceForge Revit IFC library, and how to implement this via Document.Export()? #

Yes, you can replace the built-in library with the SourceForge version, but it requires careful assembly loading and configuration. Here’s a step-by-step guide:

Step 1: Prepare your activity package #

• Download the SourceForge Revit IFC library DLLs (usually Revit.IFC.Exporter.dll and related assemblies) that match your target Revit version.
• Include these DLLs in your DA4R activity package—place them in the root directory or a subfolder you can easily reference in code.

Step 2: Load the external library and configure export #

Instead of relying on Revit’s built-in assembly, explicitly load the external exporter at runtime to ensure your code uses the SourceForge version. Here’s a code example:

using System.Reflection;
using Autodesk.Revit.DB;

public void ExportWithExternalIFC(Document doc, string outputPath)
{
    // Path to your external IFC exporter DLL (adjust based on your package structure)
    string ifcDllPath = Path.Combine(Environment.CurrentDirectory, "Revit.IFC.Exporter.dll");
    
    // Load the external assembly
    Assembly ifcExporterAssembly = Assembly.LoadFrom(ifcDllPath);
    
    // Get the IFCExportOptions type from the external library
    Type ifcExportOptionsType = ifcExporterAssembly.GetType("Autodesk.Revit.DB.IFC.IFCExportOptions");
    
    // Create an instance of the external IFCExportOptions
    object ifcExportOptions = Activator.CreateInstance(ifcExportOptionsType);
    
    // Configure export settings using reflection (since we're working with a dynamic type)
    PropertyInfo ifcVersionProp = ifcExportOptionsType.GetProperty("IFCVersion");
    ifcVersionProp.SetValue(ifcExportOptions, IFCVersion.IFC4); // Example: set export to IFC4
    
    // Run the export with the external options
    doc.Export(outputPath, "exported_model.ifc", ifcExportOptions);
}

Key caveats to remember #

• Reflection is necessary: Unless you can reference the SourceForge library directly at build time, you’ll need reflection to access and set IFCExportOptions properties.
• Load early: Make sure to load the external DLL before any calls to IFC-related APIs—DA4R might load the built-in library first otherwise.
• Test locally first: Validate your code in a headless Revit environment (using Revit’s command-line mode) before deploying to DA4R. This helps catch loading issues or configuration bugs early.
• Include all supporting files: Some SourceForge IFC library versions require extra files (like configs or helper DLLs). Double-check that everything is included in your package.

内容的提问来源于stack exchange，提问作者Volodymyr Dobrzhanskyi