The data types text and nvarchar are incompatible in the equal to operator+sql exception

I found following exception while updation.

The data types text and nvarchar are incompatible in the equal to operator


      Task_DetailsTable.Context.Refresh(RefreshMode.KeepCurrentValues, objTask);
      Task_DetailsTable.Context.SubmitChanges();


where;
  private Table Task_DetailsTable;
  
and objTask contanning the feilds of table.