c# - 更新 iQueryable 中的多行

Question

给定这张表:

我需要更新所有 4 行的 Rate 和 Average。

var currency = Context.Set<Currency>().Select(c => c);

这将创建 currency 作为 iQueryable。但现在我无法设想如何制定更新语句来更新所有四行中的 Rate 和 Average。

我需要做的是等价于此:

update Currencies set rate = 1.7, Average = 1.1 where CurrencyId = 1
update Currencies set rate = 2.5, Average = 2.1 where CurrencyId = 2
update Currencies set rate = 3.1, Average = 3.1 where CurrencyId = 3
update Currencies set rate = 42.7, Average = 42.1 where CurrencyId = 4

Answer 1

简单的方法是:

var currency1 = Context.Currency.Find(1);
curreny1.Rate = 1.7;
currency1.Average = 1.1;
//do the same for other currencies and finally save changes
Context.SaveChanges();

如果您想避免对数据库进行额外的 GET 调用以使用 id 获取货币对象，则

var currency1 = new Currency{CurrenyId = 1, Rate = 1.7, Average = 1.1 };   

var entry1 = Context.Entry(currency1);
entry1.Property(p=> p.Rate).IsModified = true;
entry1.Property(p=> p.Average).IsModified = true;

Context.SaveChanges();