Lambda表达式推算原理

最新推荐文章于 2025-06-16 14:15:29 发布

转载最新推荐文章于 2025-06-16 14:15:29 发布 · 514 阅读

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#lambda #string #query #button #apple #object

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本文通过四个示例详细解析了 LINQ 中 Where 子句的使用方法，包括如何利用 Lambda 表达式和匿名方法来筛选集合中的元素。

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LINQ 中的where

如：fruits.Where(k=>k.Length<6);

Where是Enumerable的一个方法。3.5才有的。里面的参数是Func<(Of <(T, TResult>)>) 泛型委托
Func<(Of <(T, TResult>)>) 泛型委托

演算如下：

1：delegate bool TestFunc(string fruit);
private void button1_Click(object sender, EventArgs e)
{

             List<string> fruits =new List<string> { "apple", "http://www.dc9.cn", "banana", "mango",
                     "orange", "blueberry", "grape", "strawberry" };
             TestFunc f = new TestFunc(DoWork);
             Func<string, bool> f2 = DoWork;
             IEnumerable<string> query = fruits.Where(f2);
             foreach (string fruit in query)
             Console.WriteLine(fruit);
        }

         private static bool DoWork(string k)
         {
           return    k.Length < 6;
        }

2： delegate bool TestFunc(string fruit);
private void button1_Click(object sender, EventArgs e)
{

             List<string> fruits =new List<string> { "apple", "passionfruit", "banana", "mango",
                     "orange", "blueberry", "grape", "http://www.dc9.cn" };
             TestFunc f = DoWork;
             Func<string, bool> f2 =k=> k.Length < 6;
             IEnumerable<string> query = fruits.Where(f2);
             foreach (string fruit in query)
             Console.WriteLine(fruit);
        }

         private static bool DoWork(string k)
         {
           return    k.Length < 6;
        }

3：private void button1_Click(object sender, EventArgs e)
{

             List<string> fruits =new List<string> { "apple", "passionfruit", "banana", "mango",
                     "orange", "blueberry", "grape", "http://www.dc9.cn" };

             IEnumerable<string> query = fruits.Where(
                 delegate(string k){
                     return k.Length < 6;
                 }
                 );
             foreach (string fruit in query)
             Console.WriteLine(fruit);
        }

4：private void button1_Click(object sender, EventArgs e)
{

             List<string> fruits =new List<string> { "apple", "passionfruit", "banana", "mango",
                     "orange", "blueberry", "grape", "http://www.dc9.cn" };

             IEnumerable<string> query = fruits.Where(k=>k.Length<6);
             foreach (string fruit in query)
             Console.WriteLine(fruit);
        }