Hi

TDataset.Locate did not work correctly when working with Delphi 2009 and fields that contain UTF-8 or Ansi strings having different code page as
the system code page. The reason was that the code in dbisamtb.pas assings KeyValues to the Value property of a field. In this case the field is a
TStringField and Delphi 2009 VCL is converting the Ansi string (UTF-8 or code page encodede) to UnicodeString. This causes the locate logic to
compare the the values in the database to UnicodeString when it should compare to AnsiStrings.

DBISAM does not contain WideString fields so all strings in the database are Ansi, right?

To make Locate working with strings do not just assing KeyValue to the Value property of TField but check if the field is a string field and if the
varian contains AnsiString set the AsAnsiString property instead of Value property.

The following code contains fixes marked with //JS

Line:9716
                 begin
                 if (TempField is TLargeIntField) then
                    TLargeIntField(TempField).AsLargeInt:=KeyValues
//JS
                 else if (TempField is TStringField) and (FindVarData(KeyValues)^.VType = varString) then
                    TStringField(TempField).AsAnsiString:=KeyValues
//JS
                 else
                    TempField.Value:=KeyValues;
                 end;

Best regards,
Jaakko

Two more things:

- This code should be used only with Delphi 2009 and later
- The similar code should be used few lines earlier where variant is an array variant.

Jaakko,

<< TDataset.Locate did not work correctly when working with Delphi 2009 and
fields that contain UTF-8 or Ansi strings having different code page as the
system code page. The reason was that the code in dbisamtb.pas assings
KeyValues to the Value property of a field. In this case the field is a
TStringField and Delphi 2009 VCL is converting the Ansi string (UTF-8 or
code page encodede) to UnicodeString. This causes the locate logic to
compare the the values in the database to UnicodeString when it should
compare to AnsiStrings. >>

I will check this out and make the necessary adjustments.

<< DBISAM does not contain WideString fields so all strings in the database
are Ansi, right? >>

Yes.

Thanks,

--
Tim Young
Elevate Software
www.elevatesoft.com

Jaako,

<< To make Locate working with strings do not just assing KeyValue to the
Value property of TField but check if the field is a string field and if the
varian contains AnsiString set the AsAnsiString property instead of Value
property. >>

Do you have an example project that demonstrates where the issue is ?  I'm
looking at the D2009 source, and effectively all TStringField's are already
treated as AnsiString values.  For example, the SetAsString method for the
TStringField is this:

procedure TStringField.SetAsString(const Value: string);
begin
 SetAsAnsiString(AnsiString(Value));
end;

IOW, it casts it to an AnsiString and assigns the value.  The same is true
for the variants:

procedure TStringField.SetVarValue(const Value: Variant);
begin
 SetAsString(Value);
end;

which just calls the SetAsString method.

I don't see how your code changes the behavior of the string conversions at
all.

--
Tim Young
Elevate Software
www.elevatesoft.com

Jaako,

Never mind - I wasn't thinking straight.  I now see the problem with the
conversion to and from the UnicodeString.  It causes the string to "lose"
its code page in the process if it is different from the system code page.

However, just keep in mind that this type of issue can be found all over the
VCL, so it probably isn't the only place where this type of issue exists.

--
Tim Young
Elevate Software
www.elevatesoft.com