文章目录
select
给新类型赋值
List<Students> studentsSource = new List<Students>()
{
new Students()
{
Id= 1,
Name="11",
ClassId=1,
Age=25,
},
new Students()
{
Id= 2,
Name="22",
ClassId=2,
Age=22,
},
new Students()
{
Id= 3,
Name="33",
ClassId=1,
Age=33,
},
new Students()
{
Id= 4,
Name="44",
ClassId=2,
Age=21,
},
new Students()
{
Id= 5,
Name="55",
ClassId=5,
Age=55,
},
};
var query =studentsSource.Select(x => new {id=x.Id,age=x.Age>50?999:0});
foreach (var item in query)
{
Console.WriteLine(item.id);
Console.WriteLine(item.age);
Console.WriteLine("\n");
}
join
List<StuClass> stuClasses = new List<StuClass>()
{
new StuClass{Id=1,ClassName="11"},
new StuClass{Id=2,ClassName="22"},
new StuClass{Id=3,ClassName="33"},
new StuClass{Id=4,ClassName="44"},
};
// == 要换成equals
{
var query2 = from s in studentsSource
join c in stuClasses on s.ClassId equals c.Id
select new StuAndClass {
Id=s.Id,
ClassId=s.ClassId,
Age=s.Age,
ClassName=c.ClassName,
};
var query3 = studentsSource.Join(stuClasses, s => s.ClassId, c => c.Id, (s, c) => new StuAndClass
{
Id = s.Id,
ClassId = s.ClassId,
Age = s.Age,
ClassName = c.ClassName,
});
}
其他
//获取前几条数据
//var query3 = studentsSource.Take(2);
//var query4 = studentsSource.Skip(2);
//var query5 = studentsSource.OrderBy(s=>s.Name);
var query2 = studentsSource.Select(s => s.Name);
var query6 = studentsSource.Where(s=>s.Name.Contains("1"));
