How to pass TDataset parameter

Data Abstract
1

Hello,

I have a query on client side, TDbisamQuery in particular, and i need to pass the resultset over to server side, as method parameter.

What would be the best way of doing that?

Thanks.

2

You can’t pass TDataset descendant as parameter but you can serialize it to stream with datastreamer and read it from stream on other side.

  • you can get IDADataset from TDataset descendant with TDatasetWrapper
  • write IDADataset to stream with any datastreamer like TDABin2DataStreamer
  • pass stream to other side.
  • read data from stream to TDAMemDataTable
  • TDataset descendant can be accessed like table.Dataset
3

Thanks Evgeny, any sample code available for using TDatasetWrapper?

4

just create it?

//ds: idadataset
//mydataset : tdataset;
ds:= TDatasetWrapper.Create(mydataset);
5

Arghh okay thank you.

6

Would you advice how to do this properly please?
//ADataset: TDataset
Client side:

   vDS := TDatasetWrapper.Create(ADataset);
   vDataset := Binary.Create;
   vDataStreamer := TDABin2DataStreamer.Create(NIL);
   try
      vDataStreamer.Initialize(vDataset, aiWrite);

      vDataStreamer.WriteDataset(vDS, [woRows, woSchema]);

      vResult := (RoutingService as IIdlsRoutingService).UpdateRouting(vDataset, -1, vErrorMessage);
   finally
      vDataStreamer.Finalize;
      vDataStreamer.free;
      //vDS.free;
   end;

Server side. First method parameter is of Binary type:

function TIdlsRoutingService.UpdateRouting(const ADataset: Binary; const AUpdUserID: Integer; out AErrorMessage: string): Boolean;
   var vMDT: TDADataTable;
       vIdx: integer;
begin
   vMDT := DatatableFromStream(ADataset, TDADataTable, DABin2DataStreamer1);
   try
      for vIdx := 0 to vMDT.Dataset.Fields.Count-1 do
         CodeSite.SendString('Field', vMDT.Dataset.Fields[vIdx].FieldName)
   finally
      vMDT.free
   end
end;
7

according to your task, I’d suggested to you just pass array of strings. it will be more simple and clear solution:

  • fill array on client side
  • pass it to server-side
  • process them
8

No, i need to be able to use the code on server-side which deals with TDataset.

The above code on server-side is just a testing to see how the dataset is passed.

9

check that DatatableFromStream returns TDAMemDataTable object

10

I see that the routine returns TDADataTable, but even if i change it accordingly it AVs.

var vMDT: TDADataTable;
vIdx: integer;
begin
vMDT := DatatableFromStream(ADataset, TDADataTable, DABin2DataStreamer1);
try
for vIdx := 0 to vMDT.Fields.Count-1 do
CodeSite.SendString(‘Field’, vMDT.Fields[vIdx].Name)
finally
vMDT.free
end
end;

Can you clearly show what is wrong with the code, without asking me to keep guessing?

11 
vMDT := DatatableFromStream(ADataset, TDADataTable, DABin2DataStreamer1);

specify TDAMemDataTable here

12

I tried that already.

Is it the only issue with the code that you see?

13

client-side:
your stream isn’t written correctly. correct usage is

      vDataStreamer.Finalize;
      vResult := (RoutingService as IIdlsRoutingService).UpdateRouting(vDataset, -1, vErrorMessage);

–
in testcases we use this code:

    LStream:= TMemoryStream.Create;
    try
      DABin2DataStreamer1.WriteDataset(LStream, DAMemDataTable1, [woSchema], -1);
      LStream.Position:= 0;
      LTestTable:= TDAMemDataTable.Create(nil);
      try
        DABin2DataStreamer1.ReadDataset(LStream, LTestTable, True);
        Check(CompareBytes(LTestKey, LTestTable.ParamByName('blob1').AsBytes));
      finally
        FreeAndNil(LTestTable);
      end;
    finally
      FreeAndNil(LStream);
    end;
14

Thanks Evgeny, .Finalize was a culprit.