可能很多同学和我一样对于select()和where()区别并不是太清晰，其实两者还是有本质区别的。
1、where()用法：必须加条件，且返回对象结果。
static void Main(string[] args)
{
List<Person> listPerson = new List<Person>();
listPerson.Add(new Person { Name = "Alice", Address = "北京", Age = 30 });
listPerson.Add(new Person { Name = "Joe", Address = "上海", Age = 34 });
listPerson.Add(new Person { Name = "Cat", Address = "广州", Age = 24 });
listPerson.Add(new Person { Name = "Alan", Address = "深圳", Age = 26 });
listPerson.Add(new Person { Name = "Tom", Address = "重庆", Age = 28 });
listPerson.Add(new Person { Name = "Jarrey", Address = "天津", Age = 40 });
IEnumerable<Person> results = listPerson.Where(p => p.Name.Contains("a"));//必须加条件,返回对象
foreach(var item in results )
{
Console.WriteLine(item.Name);
}
Console.WriteLine("按任意键可退出！");
Console.ReadKey();
}
结果：Cat Alan Jarrey。
Alice虽然也包含a但是是大写的A，所以输出结果是不会包含Alice。
2、select()用法：
(1)(a=>a.Value=="22")加条件查询时，返回bool型结果;
(2)(a=>a)没条件返回对象
(1)(a=>a.Value=="22")加条件查询时，返回bool型结果
static void Main(string[] args)
{
string[] arrays={"asd","abc","bbb","ccc"};
var results = arrays.Select(a => a.Contains("b"));//加条件查询时，返回bool型结果
foreach(var da in results )
{
Console.WriteLine(da);
}
Console.WriteLine("按任意键可退出！");
Console.ReadKey();
}
结果：False True True False
(2)(a=>a)没条件返回对象
static void Main(string[] args)
{
string[] arrays={"12","13","14","15"};
var results = arrays.Select(a => a);//没条件，返回所有对象;
foreach(var da in results )
{
Console.WriteLine(da);
}
Console.WriteLine("按任意键可退出！");
Console.ReadKey();
}
结果：12 13 14 15