Lambda 表达式select()和where()的区别（

原文地址：https://www.cnblogs.com/heartofrainbow/p/5700339.html

新建一个控制台程序ConsoleApplication1

1、where()用法：必须加条件，且返回对象结果。

   static void Main(string[] args)
   {
       string[] arrays={"asd","abc","bbb","ccc"};
       var results = arrays.Where(a=>a.Contains("b"));//必须加条件,返回对象

 foreach(var da in results )
 {
        Console.WriteLine(da);
 }

      Console.WriteLine("按任意键可退出！");
      Console.ReadKey();
   }

结果：abc  bbb。

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"));//1、(a=>a.Value=="22")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={"asd","abc","bbb","ccc"};
    var results = arrays.Select(a => a);//1、(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();
}