我有两个大的通用列表,都有超过300K的项目.

我循环遍历第一个列表以回读信息并为动态生成新列表的新项目,但是我需要在第二个列表中搜索并根据三个匹配条件返回一个值,如果发现要添加到列表,但是你可以想象,这样做300k * 300k次需要时间.

有什么方法可以更有效地做到这一点吗？

我的代码：

var reportList = new List<StocksHeldInCustody>();
foreach (var correctDepotHolding in correctDepotHoldings)
  {
    var reportLine = new StocksHeldInCustody();
    reportLine.ClientNo = correctDepotHolding.ClientNo;
    reportLine.Value = correctDepotHolding.ValueOfStock;
    reportLine.Depot = correctDepotHolding.Depot;
    reportLine.SEDOL = correctDepotHolding.StockCode;
    reportLine.Units = correctDepotHolding.QuantityHeld;
    reportLine.Custodian = "Unknown";
    reportLine.StockName = correctDepotHolding.StockR1.Trim() + " " + correctDepotHolding.StockR2.Trim();

    //Get custodian info

    foreach (var ccHolding in ccHoldList)
    {
      if (correctDepotHolding.ClientNo != ccHolding.ClientNo) continue;
      if (correctDepotHolding.Depot != ccHolding.Depot) continue;
      if (correctDepotHolding.StockCode != ccHolding.StockCode) continue;
      if (correctDepotHolding.QuantityHeld != ccHolding.QuantityHeld) continue;
      reportLine.Custodian = ccHolding.Custodian;
      break;
    }
    reportList.Add(reportLine);
  }

解决方法

var query = from correct in correctDepotHoldings
            join ccHolding in ccHoldList
              on new { correct.ClientNo,correct.Depot,correct.StockCode,correct.QuantityHeld }
              equals new { ccHolding.ClientNo,ccHolding.Depot,ccHolding.StockCode,ccHolding.QuantityHeld }
            // TODO: Fill in the properties here based on correct and ccHolding
            select new StocksHeldInCustody { ... };
var reportList = query.ToList();

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