In this lab, we explore the Revit document elements, and implement a class Lab2_1_Elements derived from IExternalCommand in the Labs2 module. For the Revit element exploration, we will require the use of some additional namespaces, so we add statements to include these as well.

using System;
using System.IO;
using Autodesk.Revit;
using Autodesk.Revit.Elements;
using Geo = Autodesk.Revit.Geometry;
using Autodesk.Revit.Parameters;
using Autodesk.Revit.Symbols;

using XYZ = Autodesk.Revit.Geometry.XYZ;
using XYZArray = Autodesk.Revit.Geometry.XYZArray;

namespace Labs
{
  /// <summary>
  /// List all document elements.
  /// </summary<
  public class Lab2_1_Elements : IExternalCommand
  {
    public IExternalCommand.Result Execute(
      ExternalCommandData commandData,
      ref string message,
      ElementSet elements )
    {
      return IExternalCommand.Result.Succeeded;
    }
  }
}

Imports System.IO
Imports Autodesk.Revit.Symbols
Imports Autodesk.Revit.Collections
Imports Autodesk.Revit.Geometry

Public Class Lab2_1_Elements
    Implements IExternalCommand

    Public Function Execute( _
        ByVal commandData As ExternalCommandData, _
        ByRef message As String, _
        ByVal elements As ElementSet) _
    As IExternalCommand.Result _
    Implements IExternalCommand.Execute

        Return IExternalCommand.Result.Succeeded

    End Function
End Class

Since the output will be too big for a message box, we will redirect it to a text file. We define the file pathname in a string constant and implement a separate class to manage all the constants, strings and similar resources of our project. Add a new class LabConstants to the project by right clicking on the project and selecting Add > Class... and then add the following string constant to it:

namespace Labs
{
  class LabConstants
  {
    public const string gsFilePathLab2_1 = @"c:\tmp\RevitElements.txt";
  }
}

Namespace Labs
    Module LabConstants
        Public gsFilePathLab2_1 As String = "c:\tmp\RevitElements.txt"
    End Module
End Namespace

Returning to the Lab2_1_Elements command, start by opening the file to write to:

  // Typical .NET error-checking (should be done everywhere,
  // but will be omitted for clarity in some of the following
  // labs unless we expect exceptions)
  StreamWriter sw;
  try
  {
    sw = new StreamWriter( LabConstants.gsFilePathLab2_1 );
  }
  catch( Exception e )
  {
    LabUtils.ErrorMsg( "Cannot open " + LabConstants.gsFilePathLab2_1
      + "; Exception=" + e.Message );
    return IExternalCommand.Result.Failed;
  }

    ' Typical .NET error-checking (should be done everywhere, but will be omitted
    ' for clarity in some of the following labs unless we expect exceptions)
    Dim sw As StreamWriter
    Try
        sw = New StreamWriter(gsFilePathLab2_1)
    Catch e As Exception
        MsgBox("Cannot open " & gsFilePathLab2_1 & "; Exception=" & e.Message)
        Return IExternalCommand.Result.Failed
    End Try

Finally, here is standard way of looping all document elements and writing some of their properties to the stream. Please note that this kind of loop is extremely time-consuming and should generally be avoided in an application. Further on, we will explore how to use filters to avoid it:

  try
  {
    // *ALL* elements are bundled together and accessible via Document's ElementIterator
    WaitCursor waitCursor = new WaitCursor();
    string line;
    Element elem;
    ElementIterator iter = commandData.Application.ActiveDocument.Elements;
    while( iter.MoveNext() )
    {
      elem = iter.Current as Element;
      line = "Id=" + elem.Id.Value.ToString(); // Element Id
      line += "; Class=" + elem.GetType().Name; // Element class (System.Type)
      //Debug.WriteLine( line  );

      // The element category is not implemented for all classes,
      // it may return null; for Family elements, one can sometimes
      // use the FamilyCategory property instead.
      string s = string.Empty;
      if( elem is Family && null != ((Family) elem).FamilyCategory )
      {
        s = ((Family) elem).FamilyCategory.Name;
      }
      if( 0 == s.Length && null != elem.Category )
      {
        s = elem.Category.Name;
      }
      if( 0 == s.Length )
      {
        s = "?";
      }
      line += "; Category=" + s;

      // Element Name (different meaning for different classes, but mostly implemented "logically")
      // Later, we'll see that more precise info on elements can be obtained in class-specific ways...
      line += "; Name=" + elem.Name;
      sw.WriteLine( line );
    }
  }
  catch( Exception e )
  {
    message = e.Message;
    return CmdResult.Failed;
  }

    ' *ALL* elements are bundled together and accessible via Document's ElementIterator
    Dim sLine As String
    Dim elem As Revit.Element
    Dim iter As ElementIterator = commandData.Application.ActiveDocument.Elements
    Do While (iter.MoveNext)

        ' current Element
        elem = iter.Current

        ' Element Id
        sLine = "Id=" & elem.Id.Value.ToString

        ' Element class (System.Type)
        sLine += "; Class=" & elem.GetType.Name

        ' Element Category (not implemented for all classes!)
        Dim sCatName As String = ""
        If TypeOf elem Is Family Then
            Dim f As Family = elem
            If Not f.FamilyCategory Is Nothing Then
                sCatName = f.FamilyCategory.Name
            End If
        End If
        If 0 = sCatName.Length And Not elem.Category Is Nothing Then
            sCatName = elem.Category.Name
        End If
        If 0 = sCatName.Length Then
            sCatName = "?"
        End If
        sLine += "; Category=" & sCatName

        ' Element Name (different meaning for different classes, but mostly implemented "logically")
        ' Later, we'll see that more precise info on elements can be obtained in class-specific ways...
        Dim sName As String

        sName = elem.Name
        sLine += "; Name=" & sName

        ' write the Line
        sw.WriteLine(sLine)

    Loop

Don't forget to close the file and return a valid result to Revit:

  sw.Close();
  LabUtils.InfoMsg( "Element list has been written to " + LabConstants.gsFilePathLab2_1 + "." );

    sw.Close()
    MsgBox("Elements list has been created in " & gsFilePathLab2_1 & "!")

Compile and link the project and update the Revit.ini file accordingly. Or load and run the command with the help of Add-in Manager.

Run the command and examine and discuss the contents of the created file with the course instructor and your peers.