将Linq函数存储到Variable&即时定义? [英] Store Linq function into Variable & define on the fly?

问题描述

我有一个这样的Linq查询

I have a Linq query like this

var results= StudentsList.GroupBy(x=> x.GroupID)
    .GroupBy(x=> x.Any(g=>g.IsQualified== true))
    .Select(g=> g)
    .ToList();

我想将零件x.Any(g=>g.IsQualified== true)存储到一个变量中，以便我可以根据自己的需要即时更改它(例如:x.Any(g=>g.StudentName== "John"))，而无需单独定义新的Linq查询.有可能吗?

I want to store the part x.Any(g=>g.IsQualified== true) into a variable so that I can change it on the fly (example: x.Any(g=>g.StudentName== "John") ) based on my requirement and without defining a new Linq query separately. Is that possible?

伪代码

static void SomeFunction(Func<int, int> op)
  {
        var results= StudentsList.GroupBy(x=> x.GroupID)
            .GroupBy(x=> op))
            .Select(g=> g)
            .ToList();
  }

并命名为:

SomeFunction(x => x.Any(g=>g.IsQualified== true));
SomeFunction(x => x.Any(g=>g.StudentName== "John"));
SomeFunction(x => x.Any(g=>g.Country== "USA"));

推荐答案

在dotnet提琴上的演示

解决方案1 ​​

您可以使用Func<StudentInfo, bool>来实现.

private static IEnumerable<IGrouping<int, StudentInfo>>  SomeFunction(List<StudentInfo> list, Func<StudentInfo, bool> selector)
{
    return list.GroupBy(x => x.GroupID)
                              .Where(g => g.Any(selector) )
                              .Select(g => g);
}

如何使用它?

var result1 = SomeFunction(StudentsList, p => p.IsQualified == true);
var result2 = SomeFunction(StudentsList, p => p.Student == "Adam");

解决方案2 (创建扩展方法)

Solution 2 (Create Extension method)

public static IEnumerable<IGrouping<int, StudentInfo>> ExtensionMethod_SomeFunction(this IEnumerable<StudentInfo> list, Func<StudentInfo, bool> selector) 
{
    return list.GroupBy(x => x.GroupID)
                              .Where(g => g.Any(selector) )
                              .Select(g => g);
}

如何使用它?

var result3 = StudentsList.ExtensionMethod_SomeFunction(p => p.IsQualified == true);
var result4 = StudentsList.ExtensionMethod_SomeFunction(p => p.Student == "John");

这篇关于将Linq函数存储到Variable&即时定义?的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！