No chit-chat so direct to the point.

I am trying to write a lisp for autocad civil 3D, the first step for it (where I am already stuck) is to get info from object data of a polyline (or what I suppossed is object data) to use it later.

At the beginning I am trying to just show the value of the property on the command line just to be shure it is getting it riht but I am only getting error or nil results.

The info appears in the properties window when you select the polyline (here a screenshot)
screnshot properties window on autocad civil 3D

the idea is to ge the “Thema” value, the “OD” in front of the agrupation name “OD:KLIC_Administratief” makes me think that it is Object Data.

My programing knowledge is low or null, so I am working with chatgpt in order to make it work, with no luck…

I will write the code I have now, under experts eyes it may make no sense, unfortunatelly I don’t understand half the info or functions so I am putting all my trust on chatgpt…

(defun c:GetThemaValue (/ ent objDoc objEnt objData objDataTable objRecords objRecord i fieldName fieldValue)
  ;; Prompt the user to select a polyline
  (setq ent (car (entsel "nSelect a polyline: ")))

  ;; Check if the selected entity is a polyline
  (if (and ent (= (cdr (assoc 0 (entget ent))) "LWPOLYLINE"))
    (progn
      ;; Get the active document
      (setq objDoc (vla-get-ActiveDocument (vlax-get-acad-object)))
      
      ;; Get the selected entity as a COM object
      (setq objEnt (vlax-ename->vla-object ent))

      ;; Get the collection of object data tables in the document
      (setq objData (vla-get-DataBase objDoc))
      (setq objDataTables (vla-GetObjectDataTables objData))

      ;; Check if the object data table "KLIC_Administratief" exists
      (if (setq objDataTable (vl-catch-all-apply 'vla-Item (list objDataTables "KLIC_Administratief")))
        (progn
          ;; Get the object data records of the selected entity
          (setq objRecords (vlax-invoke objDataTable 'GetObjectDataRecords objEnt))

          ;; Iterate over the records
          (if (> (vlax-safearray-get-u-bound (vlax-variant-value objRecords) 1) 0)
            (progn
              ;; Get the first record (assuming there is at least one)
              (setq objRecord (vlax-safearray-get-element (vlax-variant-value objRecords) 0))

              ;; Get the field names of the record
              (setq objFieldNames (vlax-variant-value (vlax-invoke objRecord 'GetFieldNames)))

              ;; Iterate over the field names to find "Thema"
              (setq i 0)
              (while (< i (vlax-safearray-get-u-bound objFieldNames 1))
                (setq fieldName (vlax-safearray-get-element objFieldNames i))
                (if (= fieldName "Thema")
                  (setq fieldValue (vlax-invoke objRecord 'GetField fieldName))
                )
                (setq i (1+ i))
              )

              ;; Display the value of the "Thema" field
              (if fieldValue
                (prompt (strcat "nThe value of the 'Thema' property is: " (vl-princ-to-string fieldValue)))
                (prompt "nThe 'Thema' field was not found.")
              )
            )
            (prompt "nThere are no object data records associated with this polyline.")
          )
        )
        (prompt "nThe 'KLIC_Administratief' object data table was not found.")
      )
    )
    (prompt "nThe selected entity is not a polyline.")
  )
  (princ)
)

And of course, due to my ignorance, I can’t see where is it failing.

well, I tried imploring chatgpt to make it work…

From my ignorance on this field, I have no idea what to try or do to solve this…