在单个查询中转换foreach

Question

我有一个Linq查询和一个for循环，如：

double total = 0;

IEnumerable<Dispatch> requiredDispatches = Dispatches.Where(x => x.OrderId == SelectedOrder.OrderId);
foreach(Dispatch dispatch in requiredDispatches)
{
    total += dispatch.DispatchItemTransactions.Sum(x => x.Quantity);
}

我已经尝试了但只有一半：

total = Dispatches.Where(x => x.OrderId == SelectedOrder.OrderId)
                  .Select(x => x.DispatchItemTransactions).Sum( x => x.

但在x.后，它没有向我提供我的财产Quantity。

Answer 1

您必须首先展平层次结构，使用SelectMany并查找Sum

var total = Dispatches.Where(x => x.OrderId == SelectedOrder.OrderId)
                      .SelectMany(x => x.DispatchItemTransactions)
                      .Sum( x =>x.Quantity);