Go Premium for a chance to win a PS4. Enter to Win

x
?
Solved

How I can use a TClientDataset (of VCL.NET) in a ASP.NET WebService.

Posted on 2006-07-14
9
Medium Priority
?
1,694 Views
Last Modified: 2008-01-09
Hi Experts,

After days examining different ways to consume a ADO.NET dataset sent
by a webservice method, I found that article of DrBob (http://www.drbob42.com/examines/examin62.htm)
which gave the idea to use the ADONETConnector to take the data to ClientDataset and save it to a
XML string.
The code for the function is below:
 
function ObterXMLDataPacket(
  pADONET_Dataset: DataSet; pNumero_DataTable: Integer): String;
var Conector:TADONETConnector;
    Cds:TclientDataset;
    DSP:TDatasetProvider;
    St: TStringStream;
begin
  If pADONET_Dataset.Tables.Count = 0 then Exit;
  (*Cria os componentes necessários*)
  Cds := TClientDataSet.Create(nil);
  DSP := TDataSetProvider.Create(nil);
  St := TStringStream.Create;
  Conector := TADONETConnector.Create(nil);
  (*Conecta os componentes*)
  DSP.Dataset := Conector;
  Cds.SetProvider(DSP);
  Conector.DataTable := pADONET_Dataset.Tables[pNumero_DataTable];
  (*Obtém os dados*)
  Conector.Open;


  CDS.Open;  // Here the method throws the exception


  (*Transforma os dados em XML Datapacket*)
  Cds.SaveToStream(St,dfXML);
  Result := ST.DataString;
  (*Limpa o ambientes*)
  St.Free;
  Cds.Free;
  Conector.Free;
  DSP.Free;
end;

The function is used in a WebMethod which opens a BDPDataAdapter and calls the function with the Dataset
populated by the Adapter.

Here is the code:

function TCC_DataLayer.RetornaDatasetXMLDPacket: String;
begin
  BdpDataAdapter1.Active := True;
  Result := ObterXMLDataPacket(ds1,0);
end;

With the needed units (ADONetDb, System.Data, etc among a few other ones) - the WebService build without problems. But when the method is called, the execution is aborted with a exception (on the Win32 client, on the browser gave only a internal server error).

Here is the message of the Exception: "Servidor não pôde processar a solicitação. --> Invalid threading model (STAThreadAttribute is required)"

The first part is in Brazilian Portuguese and means: "Server could not process the request"

Here is the code where the WebMethod is called:
 
procedure TForm2.Button2Click(Sender: TObject);
var Comm:THTTPRIO;
begin
  Comm := THTTPRIO.Create(nil);
  WServico := GetTCC_DataLayerSoap(False,'http://localhost/CredCob_DataLayer/uCC_DataLayer.asmx',Comm);
  try
    ClientDataSet1.XMLData := WServico.RetornaDatasetXMLDPacket;
    ClientDataSet1.Open;
  except
  on E: Exception do
    begin
    With TStringList.Create do
      begin
      Add(E.Message);
      SaveToFile('c:\mensagemerro.txt');
      Free;
      end;
    end;
  end;
end;

 
Environment: Delphi 2006 Architect (Borland® Developer Studio for Microsoft® Windows™ Version 10.0.2288.42451 Update 2), IIS + ASP.NET 1.1.4322...
DataBase: MSSQL 2005 (just for the sake of completeness).

Best Regards and thank you very much for the attention,
Fabricio (Delphian)
0
Comment
Question by:Delphian
  • 4
  • 3
9 Comments
 
LVL 12

Expert Comment

by:Ivanov_G
ID: 17114029
Have you tried this:

[STAThreadAttribute]
function TCC_DataLayer.RetornaDatasetXMLDPacket: String;
....
0
 
LVL 4

Author Comment

by:Delphian
ID: 17121919
You mean apply the attibute to the WebMethod? Does not work.
And even putting in  both (internal function and WebMethod), or
in one of them - does not work, the exception is thrown wherever
the attribute is located...

Any ideas?
0
 
LVL 12

Expert Comment

by:Ivanov_G
ID: 17122930
[STAThread]
static void Main()
{
}

This way you change the Threading Model to Single Threaded.
0
Technology Partners: We Want Your Opinion!

We value your feedback.

Take our survey and automatically be enter to win anyone of the following:
Yeti Cooler, Amazon eGift Card, and Movie eGift Card!

 
LVL 4

Author Comment

by:Delphian
ID: 17123337
No luck on this also...
0
 
LVL 12

Expert Comment

by:Ivanov_G
ID: 17123779
No more ideas on my side... Sorry.
0
 
LVL 4

Author Comment

by:Delphian
ID: 17124499
I did some additional testing, the results are:

-> In a desktop Windows Forms: OK (no changes, no additional attributes needed)
-> In a desktop VCL.NET: OK (ditto above)

The great trouble is when ASP.NET Web Services come in scene. Seems a agreement
that someone needs to get a STAThread attrib... But is not the likely ones.

So, the 500 points question: WHERE I put the this 'lovely' attribute? Or is not an attribute
question?

Any comments?

(BTW: Thank you for the good will, Ivanov)
0
 
LVL 4

Author Comment

by:Delphian
ID: 17964054
I discovered later that it's reported on Borland Quality Central at
http://qc.borland.com/wc/qcmain.aspx?d=33679

And after that I forgot the question. It's a real shame.

Since I changed the implementation, there's no use for me the
workaround on the link, but I ask you just to mantain the question
on the DB - it can help others.

But I would like the refund.

0
 
LVL 1

Accepted Solution

by:
Computer101 earned 0 total points
ID: 17983746
PAQed with points refunded (500)

Computer101
EE Admin
0

Featured Post

Industry Leaders: We Want Your Opinion!

We value your feedback.

Take our survey and automatically be enter to win anyone of the following:
Yeti Cooler, Amazon eGift Card, and Movie eGift Card!

Question has a verified solution.

If you are experiencing a similar issue, please ask a related question

The uses clause is one of those things that just tends to grow and grow. Most of the time this is in the main form, as it's from this form that all others are called. If you have a big application (including many forms), the uses clause in the in…
In my programming career I have only very rarely run into situations where operator overloading would be of any use in my work.  Normally those situations involved math with either overly large numbers (hundreds of thousands of digits or accuracy re…
Are you ready to place your question in front of subject-matter experts for more timely responses? With the release of Priority Question, Premium Members, Team Accounts and Qualified Experts can now identify the emergent level of their issue, signal…
Please read the paragraph below before following the instructions in the video — there are important caveats in the paragraph that I did not mention in the video. If your PaperPort 12 or PaperPort 14 is failing to start, or crashing, or hanging, …

885 members asked questions and received personalized solutions in the past 7 days.

Join the community of 500,000 technology professionals and ask your questions.

Join & Ask a Question