Linq 中的Select事例

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1.对查询结果进行转换。

string[] names={"ADE","Jerry","Steves"};
var ns=from s in names
            where  s.StartWiths("A")
            Select   s.ToLower();
foreare(var o  in na){
        Console.WriteLine(o);
}　　

2. 对于数组，select可以对数组元素以及索引进行操作：

  string[] names = { "Jack", "Bob", "Bill", "Catty", "Willam" };
  var rs = names.Select((name, index) => new { Name = name, Index = index });
  foreach (var r in rs)
      Console.WriteLine(r);

3. 对于集合（wpf中的mvvm为例子），查询选中项是否符合要求：

private const string LMPPropertyName="LMPSource";
private OberservableCollection<YM_LMP_SQB> _LMPSource;
public  OberservableCollection<YM_LMP_SQB>  LMPSource{

get{return _LMPSource;}
set{
if(_LMPSource==value)
     return;
RaisePropertyChanging(LMPPropertyName);
_LMPSource==value;
RaisePropertyChanged(LMPPropertyName);

}
}

int a=LMPSource.Select(
(s,index)=>new{s,index}).FirstOrDefault(w=w.s==LMPSource.Where(e=>e.ZT!="0").FirstOrDefault()).index+1;
Console.WriteLine(a)

4. 组合查询，可以对多个数据源进行组合条件查询（相当于使用SelectMany函数），下面的例子其实就相对于一个双重循环遍历：

    int[] numbersA = { 0, 2, 4, 5, 6, 8, 9 };
    int[] numbersB = { 1, 3, 5, 7, 8 };

    var pairs =
        from a in numbersA,
                b in numbersB
        where a < b
        select new {a, b};

    Console.WriteLine("Pairs where a < b:");
    foreach (var pair in pairs)
        Console.WriteLine("{0} is less than {1}", pair.a, pair.b);

 

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