我有一个用半逗号分隔的名称的字符串:
string names = "Jane;Harry";
我也有一个客户对象列表:
public class Customer
{
public string FirstName { get; set; }
public string LastName { get; set; }
}
List<Customer> customers = new List<Customer>();
customers.Add(new Customer(){FirstName="John", LastName="Doe"});
customers.Add(new Customer(){FirstName="Jane", LastName="Doe"});
customers.Add(new Customer(){FirstName="Harry", LastName="Potter"});
var query = from c in customers
select c;
如何创建仅返回名字在半逗号分隔列表中的客户的查询?
类似于T-SQLSELECT FistName FROM customer WHERE FirstName IN (list)
(某种)
嗯,您应该真正地将字符串拆分为开头-否则即使列表为“ Janet; Harry”,也将获得与“ Jane”的匹配项。
您可以做:
string[] validNames = names.Split(';');
var query = customers.Where(c => validNames.Contains(c.FirstName));
另一种选择是使用HashSet
,当列表很大时,它的性能会更好:
HashSet<string> validNames = new HashSet<string>(names.Split(';'));
var query = customers.Where(c => validNames.Contains(c.FirstName));
我在这里使用点表示法而不是查询表达式,因为当您仅应用一两个子句时,它更简单。但是,作为查询表达式,它将是:
var query = from c in customers
where validNames.Contains(c.FirstName)
select c;
List<string> firstnames = names.Split(';').ToList();
var query = from c in customers
where firstnames.Contains(c.FirstName)
select c ;
它将有所帮助
string allid =“ 11,12,13,14,15,16”;
string [] arrid = allid.Split(',');
var data = context.MyModels.Where(x => arrid.Contains(x.ProjectId.ToString()))]