迭代嵌套列表中的所有项目并返回不同类型的新列表 [英] Iterating all items in nested list and returning new list of different type

问题描述

我有一个这样的来源列表:

I have a source list like this:

class Foo {
    public int ID;
    public List<Foo> Children;
}

// Then somewhere else...
Foo root = new Foo(); // The Children is a nested list

然后我可以使用一种新类型进行更改:

Then I have a new type that I have access to make changes to:

class Bar : Foo {
    public string Name;
}

我想做的是创建一个新的Bar，它是上面的root变量的副本，但是每个项目中的Name属性都有一个值.此示例可以是默认值.

What I'd like to do is create a new Bar that is a replica of the root variable above, however has a value for the Name property in each item. It can be a default value for this example.

我已经尝试过root的Children上的LINQ的Select(...)，但是即使那是正确的路线，我也无法简化语法.

I've tried LINQ's Select(...) off the Children of the root but I can't get the syntax down, if that's even the correct route.

到目前为止，该功能仅适用于root列表中第一级子项.我需要它来遍及所有级别的儿童.

I have this so far, which only works on the first level of child items in the root list. I'd need it to go through all levels of children.

Bar = new ObservableCollection<Bar>(root.Children.Select(c => new Bar { Name = "Foo" }));

推荐答案

如果深度合理，则可以使用递归lambda和LINQ轻松完成:

If the depth is reasonable, it can easily be done with recursive lambda and LINQ:

Func<Foo, Bar> resultSelector = null;
resultSelector = source => new Bar
{
    ID = source.ID,
    Name = "Foo",
    Children = source.Children.Select(resultSelector).ToList<Foo>()
};
Foo result = resultSelector(root);

如果深度太大并导致堆栈溢出，则LINQ不适用，您可以对两个显式堆栈使用迭代方法:

If the depth is so big and is causing stack overflow, then LINQ is not applicable, you can use iterative approach with two explicit stacks:

var resultStack = new Stack<Bar>();
var childrenStack = new Stack<List<Foo>.Enumerator>();
var result = new Bar { ID = root.ID, Name = "Foo", Children = new List<Foo>() };
var children = root.Children.GetEnumerator();
while (true)
{
    while (children.MoveNext())
    {
        var child = children.Current;
        var resultChild = new Bar { ID = child.ID, Name = "Foo", Children = new List<Foo>() };
        result.Children.Add(resultChild);
        if (child.Children.Count == 0) continue;
        resultStack.Push(result);
        childrenStack.Push(children);
        result = resultChild;
        children = child.Children.GetEnumerator();
    }
    if (resultStack.Count == 0) break;
    result = resultStack.Pop();
    children = childrenStack.Pop();
}
// Here the result is fully populated

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