Delphi Tstringlist, get strings as a quoted, comma delimited string? - delphi

Question

I have a Tstringlist containing a list of keys used in a database table.
I'd like a simple way to generate one string containing all the keys, with each separated by a comma and enclosed in single quotes.
This is so that it can be used in a SQL 'IN' statement
eg WHERE FieldX IN ('One','Two','Three').
I've tried using quotechar but it is ignored when reading the commatext.
eg the following code
procedure junk;
var
SL : Tstringlist;
s : string;
begin
SL := Tstringlist.Create;
SL.Delimiter :=','; //comma delimiter
SL.QuoteChar := ''''; //single quote around strings
SL.Add('One');
SL.Add('Two');
SL.Add('Three');
try
s := SL.commatext;
showmessage(s);
finally
SL.Free;
end; //finally
end; //junk
shows the message One,Two,Three - without any quotes.
I know I can do it the long way round, as in
procedure junk;
var
SL : Tstringlist;
s : string;
i : integer;
begin
SL := Tstringlist.Create;
SL.Delimiter :=','; //comma delimiter
SL.Add('One');
SL.Add('Two');
SL.Add('Three');
try
s := '';
for I := 0 to SL.Count - 1 do
begin
s := s + ',' + '''' + SL[i] + '''';
end;
delete(s,1,1);
showmessage(s);
finally
SL.Free;
end;//finally
end;
but is there a simpler way using properties of the Tstringlist itself?

Answer 1

If you're using D2006 or later, you can use a CLASS HELPER:
USES Classes,StrUtils;
TYPE
TStringListHelper = CLASS HELPER FOR TStrings
FUNCTION ToSQL : STRING;
END;
FUNCTION TStringListHelper.ToSQL : STRING;
VAR
S : STRING;
FUNCTION QuotedStr(CONST S : STRING) : STRING;
BEGIN
Result:=''''+ReplaceStr(S,'''','''''')+''''
END;
BEGIN
Result:='';
FOR S IN Self DO BEGIN
IF Result='' THEN Result:='(' ELSE Result:=Result+',';
Result:=Result+QuotedStr(S)
END;
IF Result<>'' THEN Result:=Result+')'
END;
This code:
SL:=TStringList.Create;
SL.Add('One');
SL.Add('Two');
SL.Add('Number Three');
SL.Add('It''s number 4');
WRITELN('SELECT * FROM TABLE WHERE FIELD IN '+SL.ToSQL);
will then output:
SELECT * FROM TABLE WHERE FIELD IN ('One','Two','Number Three','It''s number 4')

Answer 2

Use sl.DelimitedText instead of sl.CommaText to make it follow your settings. CommaText will temporarily change the Delimiter and QuoteChar to some hardcoded values.

Answer 3

CommaText (and apparently also DelimitedText) can not be relied on to add the quotes, because they treat single word and multi word strings differently.
When retrieving CommaText, any string in the list that include spaces,
commas or quotes will be contained in double quotes, and any double
quotes in a string will be repeated.
There doesn't seem to be any combination with the TStringList alone, so I suggest you add the strings using QuotedStr.
Following settings work as you wish, regardless of, whether strings are single words or multi words:
SL := Tstringlist.Create;
SL.Delimiter :=','; //comma delimiter
SL.StrictDelimiter := True;
// SL.QuoteChar := ''''; //single quote around strings
// SL.Add('One');
// SL.Add('Two words');
// SL.Add('Three');
SL.Add(QuotedStr('One'));
SL.Add(QuotedStr('Two words'));
SL.Add(QuotedStr('Three'));
s := SL.CommaText; // or SL.DelimitedText;
showmessage(s);
Output is:
'One','Two words','Three'

Answer 4

The TStrings.DelimitedText methods quote only the strings when needed: when there's something link O'ne this will print as 'O''ne' - i.e. it double the quotes.
You can achieve what you want setting a convenience delimiter and the QuoteChar property to the #0 value and then replacing the delimiters with the quotes.
procedure junk;
var
sl : Tstringlist;
s: string;
begin
sl := Tstringlist.Create;
try
sl.Delimiter := '|';
sl.QuoteChar := #0;//no quote
sl.Add('On''e');
sl.Add('Two');
sl.Add('Three');
//escape the single quotes
s := StringReplace(sl.DelimitedText, '''', '''''', [rfReplaceAll]);
//replace the delimiters and quote the text
s := '''' + StringReplace(s, sl.Delimiter, ''',''', [rfReplaceAll]) + '''';
WriteLn(s);
finally
sl.Free;
end;
end;

Answer 5

I have resolved a similar issue with something like that :
s := ''' + StringReplace(sl.CommaText, ',', ''',''', [rfReplaceAll]) + '''