TfrReport.PrepareReport: EInvalidCastException

Comments

• loryn

  February 2004 edited 8:42AM

  Could I please have someone from FastReport provide or point me to some processes that could help identify a resolution to this problem?
• gordk St.Catherines On. Canada.

  February 2004 edited 8:42AM

  it could be simple like did you make the fr.inc file for 2.51 the same as the one from 2.5?
  or if in d7 turn off invalid cast warning?
  Is there more to the message?
  does it happen running in ide or outside in compiled exe?
  Many possibilities, and most of us can't read your mind, so supply as much info as you can.
  regards
• loryn

  March 2004 edited 8:42AM

  Thank you for your response. You provided me enough hints for me to actually figure out a workaround (for now).
  
  Anway, for the sake of documenting the issue, here is what was occurring:
  
  When I ran the code from within the debugger, I would get this message:

  ---

  Debugger Exception Notification
  
  Project Test.exe raised exception class EInvalidCast with message 'Invalid class typecast'. Process stopped. Use Step or Run to continue.

  ---

  
  The breakpoint was set on this line:
  
  class FR_Class
  
  procedure CreateDS
  ...
  DataSet := frFindComponent(CurReport.Owner, Desc) as TfrDataSet;
  
  And when tracing it down the call stack, the actual exception was being thrown on this line:
  
  class FR_Utils
  
  procedure FrFindComponent
  ...
  Result := Owner.FindComponent(Name)
  
  Now, the type of the component was a TwwDataSource. I was linking my TfrDBDataSet to the TwwDataSource rather than directly linking it to the TwwIBOQuery.