Delphi TValueListEditor Strings prop-ed quirk?

Investigating odd behaviour of a TValueListEditor being used to generate a filter expression for a ClientDataSet, I've traced it to a situation where if the first entry in it apparently had nothing in the Value column, it returned #13#10 as the Value, rather than ''.

In the following, the TStringlist TL is initialized with the same contents as the ValueListEditor Strings property has in my app. The Assert does not fail for the TStringlist, but it does for the ValueListEditor. These results occurred with D7 and XE4.

procedure TDefaultForm.ApplyFilter;
var
  i,
  Max : Integer;
  Key,
  Value : String;
  TL : TStringlist;
begin

  TL := TStringlist.Create;

  try
    TL.Add('Country=');
    TL.Add('Class=CON');

    for i:= 0 to TL.Count - 1  do begin
      Key := TL.Names[i];
      Value := TL.Values[Key];
      Assert(Value <> #13#10);  // succeeds for all i
    end;

    Max := ValueListEditor1.RowCount;
    for i:= 1 to Max  do begin
      Key := ValueListEditor1.Keys[i];
      Value := ValueListEditor1.Values[Key];
      //  Value := ValueListEditor1.Strings.ValueFromIndex[i-1];
      Assert(Value <> #13#10);  //Fails for i = 1!
    end;

  finally
    TL.Free;
  end;
end;

Btw, the TVLE was set up entirely in the Object Inspector: I simply dragged a TVLE off the palette, clicked Strings in the OI, clicked in the LH cell and typed 'Country' (sans quotes), pressed the Down key and typed 'Class' then right-arrow and typed 'CON'.

Obviously, I could avoid this by Value := Trim(Value), but was curious where the #13#10 was coming from.

Update: Prompted by @Deltic's answer and helpful comments, I decided to re-trace my steps and added another TVLE to my form. The following extracts from the DFM are revealing:

  object ValueListEditor1: TValueListEditor
    Left = 16
    Top = 224
    Width = 306
    Height = 135
    KeyOptions = [keyEdit, keyAdd]
    Strings.Strings = (
      'Country='#13#10
      'Class=CON')
    TabOrder = 2
  end

[...]

  object ValueListEditor2: TValueListEditor
    Left = 440
    Top = 192
    Width = 306
    Height = 246
    KeyOptions = [keyEdit, keyAdd]
    Strings.Strings = (
      'A='
      'B=ValueOfB')
    TabOrder = 5
  end

So, with hindsight, my question really boils down to how did the #13#10 get into the DFM? And then it came back to me ...

With no previous experience of the TVLE, when I set up the form, I got stuck at the point where I needed to add a second row. I tried pressing [Enter], but that did nothing, so then I tried Ctrl-Enter and that did nothing either. But repeating the exercise now has confirmed that that's how the CR/LF got into the TVLE's Strings.

So, it seems that the answer to my q is "No, the TVLE isn't broken, but its Strings property editor has a quirk regarding Ctrl-Enter". In other circs, I would consider deleting my q, seeing as it's at least partly caused by operator aberration, but perhaps it's better left to assist any others who trip over the same point.

Update #2 I see that my curiousity has earned me a -1. Fair enough, but I'm still inclined to leave this q & a in place, if only as an illustration of the fact that problems have deterministic causes, which can often be identified by simple things such as re-tracing one's steps, particularly with someone obviously knowledgeable looking over one's shoulder, as it were. Perhaps the down-voter would care to enlighten readers what help to future readers such a silent -1 is.

Solution

You have not shown how your value list editor is initialised, and I suspect that this is where your problem is. Behind a TValueListEditor is nothing more than a TStringList (strictly speaking a subclass of one, but the subclass doesn't change the fundamental behaviour w.r.t named values).

If your apparently empty value in the value list is yielding a value of #13#10 then it must be because that is the actual value that it has.

This simple test snippet verifies this:

var
  i:Integer;
  k, v:String;
begin
  ed.InsertRow('Country', '', TRUE);
  ed.InsertRow('Class', 'CON', TRUE);

  for i:= 1 to ed.RowCount - 1 do
  begin
    k := ed.Keys[i];
    v := ed.Values[k];
    ASSERT(v <> #13#10);  // Never fails
  end;
end;

Where ed is a TValueListEditor on the form.

Replace the first line of code in the above snippet with this however:

  ed.InsertRow('Country', #13#10, TRUE);

And the ASSERT() fails.

I suggest you investigate the initialisation of your value list editor. My guess is that it is being populated by reading from a file using a mechanism which is reading the entire line into a string, including the line end sequences, and the code that is adding the values for each read line is not stripping the #13#10 line terminators, resulting in the values being added as <name>=<value>#13#10 in each case.