Question

我做这样的事情，集合中的值不会改变

                [Test]
                public void EnumerableTest()
                {
                    var source = GetFoos();

                    source.First().One = "hello";

                    Assert.AreEqual(source.First().One, "hello");
    //it fails

                }

//I actually return this from a repository
                public IEnumerable<Foo> GetFoos()
                {
                    yield return new Foo() {One = "1", Two = "2", Three = true};
                    yield return new Foo() {One = "1", Two = "2", Three = true};
                    yield return new Foo() {One = "1", Two = "2", Three = true};
                }

Answer 1

这是因为每次枚举GetFoos时都会创建新实例。

Answer 2

如果您将var source = GetFoos();更改为var source = GetFoos().ToList();，则会立即（并完整）读取该列表。然后你应该能够改变这些值。

不要忘记存储更改的值，否则在下次阅读时它们会恢复。

Answer 3

这是因为您使用了yield return。

你可以写一下：

public IEnumerable<Foo> GetFoos()
{
    return new List<Foo>
    {
        new Foo { One = "1", Two = "2", Three = true },
        new Foo { One = "1", Two = "2", Three = true },
        new Foo { One = "1", Two = "2", Three = true },
    };
}

Answer 4

当您致电First()时，会创建一个新的枚举器。因此再次调用GetFoos()并返回一个新对象。

为什么我不能编辑IEnumerable的元素？

4 个答案: