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);
