where的扩展方法定义
public static IEnumerable<TSource> Where<TSource>(this IEnumerable<TSource> source, Func<TSource, bool> predicate);
Select的扩展方法定义
public static IEnumerable<TResult> Select<TSource, TResult>(this IEnumerable<TSource> source, Func<TSource, TResult> selector);
(1)自己实现where和select的扩展方法
// where自实现
public static IEnumerable<TSource> ExtenSionWhere<TSource>(this IEnumerable<TSource> source, Func<TSource, bool> predicate)
{
if (source == null)
{
throw new Exception(nameof(source));
}
if (predicate == null)
{
throw new Exception(nameof(predicate));
}
List<TSource> satisfySource = new List<TSource>();
foreach (var sou in source)
{
if (predicate(sou))
{
satisfySource.Add(sou);
}
}
return satisfySource;
}
// select 自实现
public static IEnumerable<TResult> ExtenSionSelect<TSource, TResult>(this IEnumerable<TSource> source, Func<TSource, TResult> selector)
{
if(source==null)
{
throw new Exception(nameof(source));
}
if(selector==null)
{
throw new Exception(nameof(source));
}
List<TResult> resultList = new List<TResult>();
foreach(var sou in source)
{
resultList.Add(selector(sou));
}
return resultList;
}
(2)自实现where和select调用
static void Main(string[] args)
{
List<int> list = new List<int>() { 1, 2, 3, 4, 5, 6 };
//常规写法
var selectList = list.ExtenSionWhere(p => p > 3).ExtenSionSelect(p => p.ToString()).ToList();
//自定义泛型委托写法
Func<int, bool> whereFunc = (num) => num > 3;
Func<int, string> selectFunc = (num) => num.ToString();
var selectList1 = list.ExtenSionWhere(p => whereFunc(p)).ExtenSionSelect(p => selectFunc(p)).ToList();
}
二.使用扩展方法实现链式编程
我在项目中经常使用开源的Flurl进行http请求,在进行拼装请求报文时,就会使用到链式编程
