The Building Coder: Standalone BasicFileInfo and ExtractPartAtom

I had an interesting discussion with Håvard Dagsvik of Symetri on the use of TransmissionData and standalone access to the BasicFileInfo, without the need for a valid Revit API context, in the course of which Håvard shared his Revit-independent GetFamilyXMLData method implementation, replacing the Revit API Family ExtractPartAtom method:

No document required for TransmissionData access
TransmissionData requires a valid Revit API context
Standalone GetFamilyXmlData method replacing ExtractPartAtom
Windows explorer BasicFileInfo right click utility

No Document Required for TransmissionData Access

Question: I fear I know the answer to this one already, but I will try to ask you anyway :-)

When reading TransmissionData or BasicFileInfo, you don't need a document:

From the TransmissionData, I can access the ExternalFileReference via GetLastSavedReferenceData, etc.

This works fine:

But, if I implement the same functionality in a standalone executable and use my own TransmissionData function...

It throws this exception on the first method that uses the Revit API:

No Revit process involved here, of course.

It's most probably as you have written before:

In general, as noted in both there and in the summary above, it is not possible to access Revit data or make any use whatsoever of the Revit API from outside of Revit.

Moreover, you need to be in a valid Revit API context to make any Revit API calls.

Maybe these methods still need the Revit Application or UIApplication in some way – or they are just locked for some other reason.

Or, should this work and it is just as the message says:

... one of the dependencies to RevitAPI.dll is not found?

I'm 99% sure it finds RevitAPI.dll.

After all, this seems like metadata that logically could be available without Revit.

TransmissionData Requires a Valid Revit API Context

Answer: Yes indeed, you do know the answer: use of the Revit API TransmissionData object requires a valid Revit API context.

In other words, you can read data from an unopened Revit document, but you can only do so from within a valid Revit session.

However, there are many ways of getting at the basic file info without use of the Revit API, e.g., determining RVT file version using Python, or one of the other approaches discussed there.

Standalone GetFamilyXmlData Method Replacing ExtractPartAtom

Response: That's great; I will definitely try to make use of Victor's raw data approach on BasicFileInfo.

Is it thinkable that TransmissionData and BasicFileInfo doesn't really need Revit?

That they just happen to be packaged within a larger library that overall can`t be used without Revit?

Maybe it is a just licensing policy decision, even though users always have a license.

Meaning, if those methods where refactored out, it could have worked, technically?

If so, let me be the first one who makes the request to get them refactored :-)

For example, take the Family.ExtractPartAtom method.

It exports an XML file with all family types, including parameters and values for each type.

But we don't use it.

First, because I (luckily) didn't realize that the Revit API provides this method.

Secondly, because my own custom method is much faster than ExtractPartAtom.

More importantly, it can be used without Revit, and it doesn't save to an external XML file that we don't need anyway.

It just returns the raw XML string that is parsed to JSON before it enters a database.

Method here:

/// <summary>
/// Faster ExtractPartAtom reimplementation,
/// independent of Revit API, for standalone 
/// external use. By Håvard Dagsvik, Symetri.
/// </summary>
/// <param name="family_file_path">Family file path</param>
/// <returns>XML data</returns>
static string GetFamilyXmlData(
  string family_file_path )
{
  byte[] array = File.ReadAllBytes( family_file_path );

  string string_file = Encoding.UTF8.GetString( array );

  string xml_data = null;

  int start = string_file.IndexOf( "<entry" );

  if( start == -1 )
  {
    Debug.Print( "XML start not detected: "
      + family_file_path );
  }
  else
  {
    int end = string_file.IndexOf( "/entry>" );

    if( end == -1 )
    {
      Debug.Print( "XML end not detected: "
        + family_file_path );
    }
    else
    {
      end = end + 7;

      int length = end - start;

      if( length <= 0 )
      {
        Debug.Print( "XML length is 0 or less: "
          + family_file_path );
      }
      else
      {
        xml_data = string_file.Substring(
          start, length );
      }
    }
  }
  return xml_data;
}

I added Håvard's method to the existing external command CmdPartAtom in The Building Coder samples to try this out, in release 2018.0.138.4, and cleaned up the existing code calling the built-in Revit API method ExtractPartAtomFromFamilyFile at the same time.