我遇到了一个奇怪的行为Linq:与两个linq表达式可能看起来相同我有不同的结果!如果我循环一次,我得到相同的结果,但在它上面没有发现。Linq奇怪behviour与字典
下面是代码:
Dictionary<String, String> mainDico = new Dictionary<String, String>();
mainDico.Add("key1", "value1");
mainDico.Add("key2", "value2");
List<Dictionary<String, String>> ls = new List<Dictionary<String, String>>();
Dictionary<String, String> fistDico = new Dictionary<String, String>();
fistDico.Add("key1", "value1");
fistDico.Add("key2", "value2");
Dictionary<String, String> secondDico = new Dictionary<String, String>();
secondDico.Add("key1", "other");
secondDico.Add("key2", "other");
ls.Add(fistDico);
ls.Add(secondDico);
IEnumerable<Dictionary<String, String>> failQuery = from p in ls
select p;
IEnumerable<Dictionary<String, String>> successfulQuery = from p in ls
select p;
String[] items = new String[] { "key1","key2" }; // with one element it works
foreach (var item in items)
{
String temp = mainDico[item];
failQuery = failQuery.Where(p => p[item] == temp);
successfulQuery = successfulQuery.Where(p => p[item] == mainDico[item]);
}
Console.WriteLine(successfulQuery.SingleOrDefault() != null);//True
Console.WriteLine(failQuery.SingleOrDefault() != null);//False
只需复制/粘贴你的代码,它输出true,true。 ..... –
我试了三台电脑:真,假(DOT.NET 4.0)并在您的评论后再次尝试。 – Akli
L.B.可能使用c#5.他们改变了他们处理闭包的方式:http://blogs.msdn.com/b/ericlippert/archive/2009/11/12/closing-over-the-loop-variable-considered-harmful.aspx –