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

Question

I found following exception while updation.

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

<code>
      Task_DetailsTable.Context.Refresh(RefreshMode.KeepCurrentValues, objTask);
      Task_DetailsTable.Context.SubmitChanges();
</code>

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