C#：foreach 中的yield return 失败 - 主体不能是迭代器块

使用yield return关键字在C#中进行迭代是一种方便而强大的方法，它允许我们在迭代过程中逐步返回结果。然而，有时候我们可能会在使用yield return时遇到一个错误信息："主体不能是迭代器块"。本文将探讨这个错误的原因，并提供解决方案。

csharp
public class Person
{
    public string Name { get; set; }
    public int Age { get; set; }
}

csharp
public static IEnumerable GetNames(IEnumerable people)
{
    foreach (var person in people)
    {
        yield return person.Name;
    }
}

csharp
static void Main(string[] args)
{
    var people = new List
    {
        new Person { Name = "Alice", Age = 25 },
        new Person { Name = "Bob", Age = 30 },
        new Person { Name = "Charlie", Age = 35 }
    };
    foreach (var name in GetNames(people))
    {
        Console.WriteLine(name);
    }
}

csharp
public static IEnumerable GetNames(IEnumerable people)
{
    return GetNamesIterator(people);
}
private static IEnumerable GetNamesIterator(IEnumerable people)
{
    foreach (var person in people)
    {
        yield return person.Name;
    }
}

csharp
static void Main(string[] args)
{
    var people = new List
    {
        new Person { Name = "Alice", Age = 25 },
        new Person { Name = "Bob", Age = 30 },
        new Person { Name = "Charlie", Age = 35 }
    };
    foreach (var name in GetNames(people))
    {
        Console.WriteLine(name);
    }
}