嵌套查询中的C#Linq Union Collections [英] C# Linq Union Collections in nested query

问题描述

我想用Linq表达这个片段，但是我不能全神贯注于它. _gameTableEntries基本上是具有字段long tableId和ICollection<object> connectedClients

I would like to express this snippet in Linq but I cannot wrap my mind around it. _gameTableEntries is basically a tuple with fields long tableId and ICollection<object> connectedClients

private ICollection<GameTableEntry> _gameTableEntries = new (...);

public ICollection<ConnectionHandler> GetConnectedClients(long tableId)
{
    HashSet<ConnectionHandler> set = new HashSet<ConnectionHandler>();

    foreach (var tableEntry in _gameTableEntries)
    {
        if (!tableEntry.TableId.Equals(tableId)) continue;

        foreach (var handler in tableEntry.ConnectedClients)
        {
            if (!handler.IsConnected) continue;

            set.Add(handler);
        }
    }

    return set;
}

推荐答案

您可能会通过

You are possibly after something like this with SelectMany

将序列的每个元素投影到IEnumerable并展平 产生的序列变成一个序列.

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

public ICollection<ConnectionHandler> GetConnectedClients(long tableId)
  => _gameTableEntries.Where(x => x.TableId == tableId)
                      .SelectMany(x => x.ConnectedClients)
                      .Where(x => x.IsConnected)
                      .ToHashSet();

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