Solved

Post to BLOB in MS Access using TADODataset

Posted on 2002-06-06
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444 Views
Last Modified: 2012-06-21
Here is my code:
procedure TForm1.btnAddBlobClick(Sender: TObject);
var
st1:TStream; //ole1:Olecontainer, rst:TADODataSet in my form, rst.Fields[0]=blob

begin
   try
      ole1.InsertObjectDialog;
      rst.Append;
      st1:=rst.CreateBlobStream(rst.Fields[0],bmReadWrite);
      ole1.SaveToStream(st1);
            rst.Post;
   finally
      st1.Free;
   end;
end;

I am getting error that empty row can not be inserted. What's wrong?


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Comment
Question by:bogiboy
6 Comments
 
LVL 12

Expert Comment

by:Lee_Nover
ID: 7060129
you probably have some fields in the table that MUST have a value
0
 
LVL 1

Author Comment

by:bogiboy
ID: 7060557
only fields that i have are Key (autoinc) and BLOB, also, I tried with BLOB foield as the only one in the table...same problem
0
 
LVL 12

Expert Comment

by:Lee_Nover
ID: 7060601
weird
have you tried using .Insert ?
I had the same problem but I don't remember how I solved it :)
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LVL 6

Expert Comment

by:swift99
ID: 7061185
I remember having the same problem and it went away when I switched to any non-Access DBMS.  At that point I stopped using Access as a back end for my own apps.
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LVL 27

Accepted Solution

by:
kretzschmar earned 100 total points
ID: 7061217
access stores blobs with an ole-server information prefix.

if there is no need to access the content within the access-frontend, then you should be able to store
your content simple with

tblobfield(dataset.fieldbyname('fieldname')).loadfromfile('filename');  //or loadfromstream

savetofile/savetostream for the other direction

meikl ;-)
0
 
LVL 1

Author Comment

by:bogiboy
ID: 7062592
Kretzschmar, you answered my problem. Using st1:=rst.CreateBlobStream(Tfield,mode) I couldn't do anything, but using TBlobField(...) syntacs -it works. Still wondering why.
NOTE: Make sure that you declare stream as TMemoryStream, not TStream to load document into OleContainer. When used TStream, I got "Stream read error" so I did typecast in OpenDoc procedure and it started to work. The same applies to AddDoc procedure.

Here is my code to:
1) Load document and post it to a blob field
2) Load it from DB and run it using OLEContainer

procedure TForm1.btnAddClick(Sender: TObject);
var
st:TMemoryStream;
begin
try
 st:=TMemoryStream.Create;
rst.Open;
Ole1.SaveToStream(St);
rst.Append;
TBlobField(rst.FieldByName('Document')).LoadFromStream(st);
rst.Post;
   finally
    st.Free;
  end;
end;

procedure TForm1.ButtonOpenDoc(Sender: TObject);
var
str:TMemoryStream;
begin
   try
   str:=TMemoryStream.Create;
   str:=TMemoryStream(rst.CreateBlobStream(rst.FieldByName('Document'),bmRead));
   ole1.LoadFromStream(str);
   ole1.Iconic:=False;
   ole1.DoVerb(0);
   finally
      str.Free;
   end;
end;
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