转换为表达式

Question

如何将此方法转换为可在linq中用于实体的Expression：

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

谢谢！

Answer 1

这是解决方案：

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

Answer 2

为什么不改为执行Contains（）查询 - 从List<long>中提取AdditionsPrices：

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

然后在EF Contains()查询中使用它：

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