我们将现有的MVC6 EF6应用程序移植到核心.
在EF核心中有一个简单的方法来更新多对多的关系吗？
来自EF6的旧代码,我们清除列表并用新数据覆盖它不再有效.
- var model = await _db.Products.FindAsync(vm.Product.ProductId);
- model.Colors.Clear();
- model.Colors = _db.Colors.Where(x =>
- vm.ColoRSSelected.Contains(x.ColorId)).ToList();
解决方法
这对你有用.
让班级有关系
- public class ColorProduct
- {
- public int ProductId { get; set; }
- public int ColorId { get; set; }
- public Color Color { get; set; }
- public Product Product { get; set; }
- }
将ColorProduct集合添加到Product和Color类
- public ICollection<ColorProduct> ColorProducts { get; set; }
- public static void TryUpdateManyToMany<T,TKey>(this DbContext db,IEnumerable<T> currentItems,IEnumerable<T> newItems,Func<T,TKey> getKey) where T : class
- {
- db.Set<T>().RemoveRange(currentItems.Except(newItems,getKey));
- db.Set<T>().AddRange(newItems.Except(currentItems,getKey));
- }
- public static IEnumerable<T> Except<T,TKey>(this IEnumerable<T> items,IEnumerable<T> other,TKey> getKeyFunc)
- {
- return items
- .GroupJoin(other,getKeyFunc,(item,tempItems) => new { item,tempItems })
- .SelectMany(t => t.tempItems.DefaultIfEmpty(),(t,temp) => new { t,temp })
- .Where(t => ReferenceEquals(null,t.temp) || t.temp.Equals(default(T)))
- .Select(t => t.t.item);
- }
使用它看起来像这样
- var model = _db.Products
- .Include(x => x.ColorProducts)
- .FirstOrDefault(x => x.ProductId == vm.Product.ProductId);
- _db.TryUpdateManyToMany(model.ColorProducts,vm.ColoRSSelected
- .Select(x => new ColorProduct
- {
- ColorId = x,ProductId = vm.Product.ProductId
- }),x => x.ColorId);
