转换为表达

Question

我怎么能这种方法转换为表达我可以在使用LINQ到实体：

public bool IsMatch(long additionId) 
    { 
     return AdditionsPrices.Any(x => x.AdditionId == additionId); 
    } 

谢谢！

Answer 1

这就是：

List<long> additionIds = AdditionsPrices.Select(x => x.AdditionId) 
             .ToList(); 

，然后在EF Contains()查询使用解决方案：

public Expression<Func<Addition, bool>> IsMatch(long additionId) 
    { 
     return a => a.AdditionsPrices.Any(x => x.AdditionId == additionId); 
    } 

Answer 2

为什么你不只是做了一个contains（）查询，而不是 - 提取List<long>从AdditionsPrices：

var results = context.SomeEntitySet 
        .Where(x => additionIds.Contains(x.AdditionId));