后代的Xdocument问题 [英] Xdocument problem with descendants

问题描述

string myTown = document.Element("GeocodeResponse").Element("result").Elements("address_component").Where(x => (string)x.Element("type").Value == "locality").Select(x => x.Element("long_name").Value).First();

工作正常，但

works fine but

List<GeocoderLocation> geoList = new List<GeocoderLocation>();
                        geoList = (from result in document.Descendants("result")
                                  select new GeocoderLocation
                                  {
                                      Town = result.Elements("address_component").Where(x => (string)x.Element("type").Value == "locality").Select(x => x.Element("long_name").Value).First(),
                                      
                                  }).ToList();

才不是.它引发异常InvalidOperationException Sequence不包含任何元素.

这是尝试解析Google http://maps的地理编码. googleapis.com/maps/api/geocode/xml?address=miry%20ln%20uk&sensor=false [

does not. It throws exception InvalidOperationException Sequence contains no elements.

This is attempt to parse geocode from google http://maps.googleapis.com/maps/api/geocode/xml?address=miry%20ln%20uk&sensor=false[^]
Why?

推荐答案

我的糟糕.我以为它是第一次抛出异常.但这没有，问题的原因是某些节点不包含邮政编码或其他内容，因此为空.

解决方案:代替.First()使用.FirstOrDefault()

My bad. I assumed that it was throwing exception on first go. But it didn''t and the cause of problem was that some nodes didn''t contain postcode or something else and therefore being empty.

Solution: instead of .First() use .FirstOrDefault()

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