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Linq:First FirstOrDefault
using System; using System.Collections.Generic; using System.Linq; using System.Text; using System.Data; using System.Reflection; namespace TestConsole { public class Program { public static void Main(string[] args) { var classify_list = new List<Alliance_FAQ_Classify> { new Alliance_FAQ_Classify{ClassifyID =1,ClassifyName ="酒店"}, new Alliance_FAQ_Classify{ClassifyID =2,ClassifyName ="机票"}, new Alliance_FAQ_Classify{ClassifyID =3,ClassifyName ="团购"}, new Alliance_FAQ_Classify{ClassifyID =5,ClassifyName ="旅游"}, new Alliance_FAQ_Classify{ClassifyID =8,ClassifyName ="Other"} }; var info_list = new List<Alliance_FAQ_Info> { new Alliance_FAQ_Info{FAQID =1,ClassifyID =1}, new Alliance_FAQ_Info{FAQID =2,ClassifyID =1}, new Alliance_FAQ_Info{FAQID =3,ClassifyID =1}, new Alliance_FAQ_Info{FAQID =4,ClassifyID =1}, new Alliance_FAQ_Info{FAQID =5,ClassifyID =1}, new Alliance_FAQ_Info{FAQID =6,ClassifyID =1}, new Alliance_FAQ_Info{FAQID =7,ClassifyID =2}, new Alliance_FAQ_Info{FAQID =8,ClassifyID =2}, new Alliance_FAQ_Info{FAQID =9,ClassifyID =2}, new Alliance_FAQ_Info{FAQID =10,ClassifyID =3}, new Alliance_FAQ_Info{FAQID =11,ClassifyID =3}, new Alliance_FAQ_Info{FAQID =12,ClassifyID =3}, new Alliance_FAQ_Info{FAQID =13,ClassifyID =3}, new Alliance_FAQ_Info{FAQID =14,ClassifyID =3}, new Alliance_FAQ_Info{FAQID =15,ClassifyID =3}, new Alliance_FAQ_Info{FAQID =16,ClassifyID =3}, new Alliance_FAQ_Info{FAQID =17,ClassifyID =3}, new Alliance_FAQ_Info{FAQID =18,ClassifyID =3}, new Alliance_FAQ_Info{FAQID =19,ClassifyID =5}, new Alliance_FAQ_Info{FAQID =22,ClassifyID =5} }; Alliance_FAQ_Classify faq = classify_list.Where(x => x.ClassifyID == 50).First(); Alliance_FAQ_Classify faq2 = classify_list.Where(x => x.ClassifyID == 50).FirstOrDefault(); string str = classify_list.Where(x => x.ClassifyID == 50).FirstOrDefault().ClassifyName.ToString(); Console.ReadLine(); } } public class Alliance_FAQ_Info { public int FAQID { get; set; } public int ClassifyID { get; set; } } public class Alliance_FAQ_Classify { public int ClassifyID { get; set; } public string ClassifyName { get; set; } } }
第一个faq报错
faq2为null
str报错
其实是很简单的东西,就是没有注意
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