Question

I’m working with an xml document in C# that has multiple (100+) points of stock market data. I’d like to create objects and add them to a List<> by passing initialization values retrieved from an xml document via linq. At the moment I’m just able to run a linq query and return one of the xml fields, in the code below, the attribute “symbol.” I’d also like to return the document’s “LastTradeDate, DaysLow, DaysHigh, LastTradePriceOnly, Open, and Volume.” From there, my custom constructor is: StockDataPoint(Symbol, TradeDate, Open, High, Low, Close, Volume). A nudge in the right direction would be great. Here’s the current linq:

var makeInfo =
      from s in doc.Descendants("quote")
      where s.Element("LastTradeDate") != null
      && s.Attribute("symbol") != null
      let dateStr = s.Element("LastTradeDate").Value
      where !string.IsNullOrEmpty(dateStr)
      && DateTime.Parse(dateStr, enUS) == targetDate
      select s.Attribute("symbol").Value;

Answer 1

Well it depends on your XML format, but you might just want something like:

...
select new StockDataPoint((string) s.Attribute("symbol"),
                          (DateTime) s.Attribute("TradeDate"),
                          (decimal) s.Attribute("Open"),
                          (decimal) s.Attribute("High"),
                          (decimal) s.Attribute("Low"),
                          (decimal) s.Attribute("Close"),
                          (long) s.Attribute("Volume"));

Note that by use the explicit operators on XAttribute, you can avoid performing the parse yourself. Indeed, you can use this earlier in your query too:

var makeInfo = from s in doc.Descendants("quote")
               where s.Attribute("symbol") &&
                     (DateTime?) s.Attribute("LastTradeDate") == targetDate
               select ...

If the target of the cast is a nullable type (either a nullable value type or a reference type) then if the attribute is missing, the result will be the null value for that type, which is very handy.