Checking previous values of properties

You can use the DataRowExtensions like this:

            Product p;
            string curValue = p.ProductName;
            string origValue = p.Field<string>(Product.ProductNameEntityColumn.ColumnName, DataRowVersion.Original);

or you can just use standard ADO.NET like this:

            Product p;
            string curValue = p.ProductName;
            string origValue = (string)p[Product.ProductNameEntityColumn.ColumnName, DataRowVersion.Original];

Of course, if you use ADO.NET like this, you'll have to perform your own DBNull checking if the column in question allows null values.