ASCII to UTF-8 conversion and displaying in a list box

I have found that national characters like ÄÖüß and so on do not show correctly in a UTF-8 coded managed application when read from an ASCII file created by a native app.

Based on an answer I read here on encoding I came up with this code:

method-id UTF_conversion.
procedure division.

*> Specify the code page to correctly interpret byte values
set wsEncoding to type Encoding::GetEncoding(1252) *> Windows
set codePageValues to Auftragrec *> sequential file to be displayed
set n3 to codePageValues::Length *> set Original length of ASCII
set tAUFTRAGrec to Auftragrec *> save record to temporary record
*> Same content is now encoded as UTF-8
set unicodeValues to wsencoding::GetString(codePageValues)
set cAUFTRAGrec to unicodevalues *> for Display 
*> Same content "äöüß" is stored as UTF-8

initialize Auftragrec
set A-Empfaenger to cA-Empfaenger *> set item containing national characters displayed in list box as only data
set Auftragpath to Auftrags-datei *> save path for temporary usage
set Auftrags-datei to Tempdatei
invoke type System.IO.File::WriteAllText(Auftrags-datei, unicodeValues)
set compareValues to type System.IO.File::ReadAllBytes(Auftrags-datei)
set n4 to compareValues::Length *> new unicode length
subtract n3 from n4 giving n2 *> add n2 to length of display item in Listbox

call "CBL_DELETE_FILE" using Auftrags-datei
returning return-code
* reset values
set Auftragrec to tAuftragrec
set Auftrags-datei to AuftragPath

end method.

it is quite awkward and my question is: Can I get the new length without saving and re-reading the file? It is necessary because the national characters don't seem to be recognized as such in a list box and without setting the field length to - length No. of national chars - the displayed fields vary in size.

I cannot just convert and save the file because when printing, the result of CHAR to OEM conversion doesn't work.

But maybe I'm just using the wrong code?