One or more rows contain values violating non-null, unique, or foreign-key constraints

Hi. i was Trying To read report and i got this error through reportviewer

I'm No sure of wats wrong. I tried Searching the net it seems to be the Dataset Prob. But im positive Dataset is working as im using VWD dataset to bind data. even had a preview Which get the data i want. So it means its working. Which then shows that its Reportviewer thats gibing me this error.

Appreciate any help thx

• "An error has occurred during report processing.
  • Exception has been thrown by the target of an invocation.
    • Failed to enable constraints. One or more rows contain values violating non-null, unique, or foreign-key constraints. "