c# - 用 Linq 替换嵌套循环

Question

在下面的查询中，我确实计算了联赛 1 中所有足球队的总值(value)。我提出的解决方案虽然有效，但看起来相当庞大。

我想找到一种更好的方法，即像这样的单行 linq 查询:

footballteams.Where(x => x.League == 1).Sum(x => x.Networth);

我当前的代码:

List<IGrouping<int, FootballTeam>> footballTeams = context.FootballTeam
    .GetQueryable()
    .GroupBy(x => x.TeamName)
    .ToList();

var prem = footballTeams.Where(x => x.League == 1).ToList();
var totalWealth = 0;

foreach (var team in prem)
{
    foreach(var singleteam in team)
    {
         totalWealth = totalWealth + singleteam.networth;
    }
}

Answer 1

使用SelectMany然后 Sum。

var totalWealth = footballTeams.Where(x => x.League == 1)
                               .SelectMany(x => x.Select(e => e.networth))
                               .Sum();

SelectMany() 摘录:

Projects each element of a sequence to an IEnumerable and flattens the resulting sequences into one sequence.