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Topic: CreateBlobStream problem?

Forum List » AnyDAC » v 1.x General English

geomagas
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CreateBlobStream problem?

Posted: 2007/09/25 05:42

Hello,
I have this piece of code in my app.


 With TADQuery.Create(Self) do
  Begin
  Connection:=someADConnection;
  SQL.Text:=someQuery; // returns 1 row
  Open;
  bs:=CreateBlobStream(FieldByName('CONTENT'),bmWrite);
  With bs do
    Begin
    Write(Body,SizeOf(Body));
    Free;
    end;
  Close;
  Free;
  End;

bs is a TStream and Body is a String.
When, at runtime, execution reaches bs:=CreateBlobStream(FieldByName('CONTENT'),bmWrite), it raises an "Invalid typecast".
Which BTW is not the case when I use i.e. TADOQuery etc.
I tried to figure out what's wrong, but no luck so far...
Any ideas?

Magafourakis George
TEI of Crete
Greece

Diman

Admin

Posts: 1482

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Re:CreateBlobStream problem?

Posted: 2007/09/25 06:00

Hello

What is your DBMS and how is idefined field CONTENT ? Looks like AnyDAC does not create for it TBlobField, but TStringField. If so, then you can just write: FieldByName('CONTENT').AsString := Body.

Regards,
Dmitry

geomagas
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Re:CreateBlobStream problem?

Posted: 2007/09/26 00:01

You are right, I forgot to give you this info.
The DBMS is MSSQL2000 and the field CONTENT is defined as varbinary(8000).
Putting a string in that field is one of many possibilities. It is defined that way so that it can accept anything, from an integer to a video clip...

Magafourakis George
TEI of Crete
Greece

Diman

Admin

Posts: 1482

Karma: 19

Re:CreateBlobStream problem?

Posted: 2007/09/26 01:42

1) AnyDAC will define this field as ftVarBinary and will create for it TVarBytesField. Current AnyDAC version does not support CreateBlobStream for non TBlobField's. Possible workarounds:
a) Set FormatOptions.MaxStringSize to values less than 8000. Then all string / binary fields with length greater than 8000 will be defined as blob fields.
b) Include following code, which will force all binary fields to be defined as blobs:


 with ADQuery1.FormatOptions do begin
  OwnMapRules := True;
  with MapRules.Add do begin
    SourceDataType := dtByteString;
    TargetDataType := dtBlob;
  end;
end;

2) AnyDAC 2.0.3 will have fix for that.

Regards,
Dmitry

geomagas
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Re:CreateBlobStream problem?

Posted: 2007/09/26 05:25

Hi,
Just to let you know, solution (b) worked fine!
I didn't test (a), (b) seemed more reasonable.
I hope 2.0.3 comes out soon, to improve a work already well done!

Thanks again
Magafourakis George
TEI of Crete
Greece

Forum List » AnyDAC » v 1.x General English