FileOpen, FileRead, FileWrite

Question

How to properly work with FileRead, FileWrite, buffers (or with TFileStream).

I need to read a whole text file to a String, then to write back a String to this file

Answer 1

TStringList is what you want if you need to deal with the file on a per-line basis.

If you just want to treat it as a single string blob then there is TStringStream.

Stream := TStringStream.Create('', TEncoding.UTF8);
Try
  Stream.LoadFromFile('c:\desktop\in.txt');
  ShowMessage(Stream.DataString);

  Stream.Clear;
  Stream.WriteString('Greetings earthlings!');
  Stream.SaveToFile('c:\desktop\out.txt');
Finally
  Stream.Free;
End;