Adding validation and business rule on DataTable

Open Dataset Designer , right click on the DataTable you wanted.
it will create partial class YourDataTableName.
and then on the
Create your Validation Sub
For instance
void CheckWorkTypeID(DirectCostRow directcostrow)
{
if (directcostrow.WorkTypeID == 0 || directcostrow.WorkTypeID == DBNull.Value)
{
directcostrow.SetColumnError("WorkTypeID", "Please Input A WorkTypeID");
}
}