Linq 条件查询的一些方法

1.LINQ的IN：
var queryResult = from p in db.Products
where (new int?[] {1,2}).Contains(p.CategoryID)
select p;

2.LINQ的NOT IN：
var queryResult = from p in db.Products
where !(new int?[] { 1, 2 }).Contains(p.CategoryID)
select p;

3.LINQ的NOT IN 遍历集合

List<string> source = new List<string>{ "aaa", "bbb" };        

List<string> px = new  List<string> { "aaa", "bbb", "ccc" }; 

 var q = from s in source   

        from p in px                  

         where s==p        

          select s;

4.SQL中的in和not in语法对应的LINQ写法

    List<testInfo> listAll = new List<testInfo>();  
    listAll.Add(new testInfo() { id = 1, name = "11", test = "111" });  
    listAll.Add(new testInfo() { id = 2, name = "22", test = "222" });  
    listAll.Add(new testInfo() { id = 3, name = "33", test = "333" });  
    listAll.Add(new testInfo() { id = 4, name = "33", test = "333" });  
      
    List<testInfo> listFind = new List<testInfo>();  
    listFind.Add(new testInfo() { id = 1, name = "44", test = "111" });  
    listFind.Add(new testInfo() { id = 2, name = "22", test = "222" });  
    listFind.Add(new testInfo() { id = 3, name = "33", test = "333" });  
    listFind.Add(new testInfo() { id = 4, name = "55", test = "333" });  
    //SQL中的in和not in语法对应的LINQ写法  
   //相当于查询语句：select * from listAll p where p.name not in(select f.name from listFind)  
    var a = (from p in listAll  
             where !(from f in listFind select f.name).Contains(p.name)  
             select p).ToList();