ODBC/TSQLQuery:TWideStringField.AsString returns '???'
lazarus / 16-Databases

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tk · 2009-10-01 10:49

Hi,
I'm testing a connection to my MSSQL database via Lazarus
TODBCConnection/TSQLQuery/TSQLTransaction. I cannot display my
nvarchar columns properly. For example in my TDBEdit I get '???' for
these columns and any record. I discovered the problem is located at
TWideStringField.AsString which returns '???' instead of valid text.
The same result I get for TWideStringField.AsWideString.

Has anybody similar experience?

Thx

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Zoran · 2009-10-01 16:53

Try using UTFEncode function.
Perhaps putting the Field's OnGetText event would be the best for you.
Something like this:

Quoteprocedure TForm1.SQLQuery1Field1GetText(Sender: TField;
  var aText: string; DisplayText: Boolean);
begin
  aText := UTF8Encode(Sender.AsString);
end;

After that you can use Field1.AsString normally.

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tk · 2009-10-01 21:21

I tried now and didn't get expected results. It seems to be a FPC
problem. The dataset (or something else) assigns a TWideStringField
for a table field that is natively not UTF16. I tried the following
code and got expected text in S for this case:

Code: [Select]var
  S: string;
...
SetLength(S, AField.DataSize);
AField.GetData(@S[1], True);
...

Of course I cannot use this because in other cases where fields are
natively in UTF16 format this would not work. Perhaps I should place
new issue in FPC bugtracker later.

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Zoran · 2009-10-02 07:00

Did you look in the LConvEncoding unit? Apart from functions for
converting particular character sets, in that unit you can also find
the function named GuessEncoding. I haven't tried this function, maybe
it can help you determine whether the string you got from database is
UTF16 or not, and if not, which encoding it is.

I don't know... I hope that someone better experienced in this than me
will have to say something to help you.

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calvarez · 2009-11-06 13:04

I'm trying to connect to a MSSQL server from Linux. You could connect
mssql from linux?

Thanks for your time.