[TableName("Categories")]
public class Category
{
    [PrimaryKey, Identity] public int    CategoryID;
                           public string CategoryName;
    [Nullable]             public string Description;
    [Nullable]             public Binary Picture;

    [Association(ThisKey="CategoryID", OtherKey="CategoryID")]
    public List<Product> Products;
}

public class Category
{
    public int    CategoryID;
    public string CategoryName;
    public string Description;
    public Binary Picture;

    public List<Product> Products;
}

public class CategoryMap : FluentMap<Category>
{
    public CategoryMap()
    {
        TableName("Categories");
		PrimaryKey(_ => _.CategoryID).Identity();
		Nullable(_ => _.Description);
		Nullable(_ => _.Picture);
		Association(_ => _.Products,_ => _.CategoryID).ToMany((Product _) => _.CategoryID);
    }
}

public static void Main()
{
    FluentConfig
	    .Configure(Map.DefaultSchema)
		    .MapingFromAssemblyOf<Category>();
}