Question

I need to use a DLL created using .NET framework. This DLL is made COM visible.

I want to use this DLL in an application created using Delphi 2006. I have followed following steps:

1. Registered the DLL using regscr32.

2. Imported the type library using Delphi IDE. It created _TLB.pas file. Following signature was created in TLB file.

    function TValidationRequest.Process(var meterBSN: WideString; var NICSerial: WideString;                                      var partNumber: WideString; var otherConfig: WideString;                                      out returnMessage: WideString): Smallint; begin   Result := DefaultInterface.Process(meterBSN, NICSerial, partNumber, otherConfig, returnMessage); end; 

3. I tried to call the method using following code snippet.

 procedure TForm1.buttonClick(Sender: TObject); var   valReq: TValidationRequest;   s1, s2, s3, s4, s5: WideString;   o: WideString; begin   valReq := TValidationRequest.Create (Self);   try     valReq.Process (s1, s2, s3, s4, o);     MessageDlg(o, mtInformation, [mbOK], 0);   finally     valReq := nil;   end; end; 

But I get following error when Process method is called.

Please can you suggest any solution?

Answer 1

Try initializing the WideStrings (s1,s2,s3,s4, and maybe even o). If I recall correctly, they are dynamic in Delphi and nil (000000000) before you set them up.