protected void HighlightCheapProducts_RowDataBound(object sender, GridViewRowEventArgs e)
{
    // Make sure we are working with a DataRow
    if (e.Row.RowType == DataControlRowType.DataRow)
    {
        // Get the ProductsRow object from the DataItem property...
        Northwind.ProductsRow product = (Northwind.ProductsRow)
            ((System.Data.DataRowView)e.Row.DataItem).Row;
        if (!product.IsUnitPriceNull() && product.UnitPrice < 10m)
        {
            e.Row.CssClass = "AffordablePriceEmphasis";
        }
    }
}

However, when the GridView is rendered with the adapter, "AffordablePriceEmphasis" is ignored completely. In the source code of GridViewAdapter.cs, in the method GetRowClass, the first line is

    string className = "";

I simply replaced it with

    string className = row.CssClass;

 and now it works as expected. It would be nice to see this changed in the CodePlex source as well. Note that this does not overwrite anything, it simply adds a second class like

    <tr class="AffordablePriceEmphasis AspNet-GridView-Alternate">

Cheers!

Could you post these details on the CodePlex Issue Tracker for the project? That way it'll constantly be in our faces to review and implement the proposed fix.

 Thanks!