static void Print(PictureCategory cat, int level)
{
StringBuilder sb = new StringBuilder();
Console.WriteLine("{0}{1}", sb.Append(' ', level).ToString(), cat.Name);
cat.SubCategories.ForEach(child => Print(child, level + 1));
}
static void Main(string[] args)
{
using (var context = new EF6RecipesContext())
{
var louvre = new PictureCategory {
Name = "Louvre"
};
var child = new PictureCategory {
Name = "Egyptian Antiquites"
};
louvre.SubCategories.Add(child);
child = new PictureCategory {
Name = "Sculptures"
};
louvre.SubCategories.Add(child);
var paris = new PictureCategory {
Name = "Paris"
};
paris.SubCategories.Add(louvre);
var vacation = new PictureCategory {
Name = "Summer Vacation"
};
vacation.SubCategories.Add(paris);
//context.PictureCategories.Add(paris); 原书中代码存在问题
context.PictureCategories.Add(vacation);
context.SaveChanges();
}
using (var context = new EF6RecipesContext())
{
var roots = context.PictureCategories.Where(c => c.ParentCategory == null);
//此时对象不是List<>所以不能直接使用ForEach（）方法
roots.ToList().ForEach(root => Print(root, 0));
}
Console.ReadKey();
}
