private void filterControl1_CreateCustomRepositoryItem(object sender, DevExpress.XtraEditors.Filtering.CreateCustomRepositoryItemEventArgs e)
 {
     if (e.Column.FieldName == "CategoryName")
     {
         RepositoryItemComboBox riComboBox = new RepositoryItemComboBox();
         using (NWindDataContext context = new NWindDataContext()) {
             riComboBox.Items.AddRange(
                 context.Categories
                 .Select(c => c.CategoryName)
                 .ToList()
                 );
         }
         e.RepositoryItem = riComboBox;
     }
 }
 public Form1()
 {
     InitializeComponent();
     using (NWindDataContext context = new NWindDataContext()) {
         Products = context.Products
                    .Include("Category")
                    .Select(p => new ProductAggregate {
             ProductName     = p.ProductName,
             CategoryName    = p.Category.CategoryName,
             QuantityPerUnit = p.QuantityPerUnit,
             UnitPrice       = p.UnitPrice.Value,
             UnitsInStock    = p.UnitsInStock.Value,
             UnitsOnOrder    = p.UnitsOnOrder.Value
         })
                    .ToList();
     }
 }