ObservableCollection< T> .Move（int，int）如何工作？ [英] How does ObservableCollection<T>.Move(int,int) work?

问题描述

我似乎无法阅读ObservableCollection的文档来弄清楚这一点MSDN上的.Move（int oldIndex，int newIndex）：

I can't seem to figure this one out by reading the documentation for ObservableCollection.Move(int oldIndex, int newIndex) on MSDN:

oldIndex类型：System.Int32从零开始的索引指定
的位置要移动的项目。 newIndex类型：System.Int32从零开始的
索引，用于指定项目的新位置。

oldIndex Type: System.Int32 The zero-based index specifying the location of the item to be moved. newIndex Type: System.Int32 The zero-based index specifying the new location of the item.

我不了解它是如何工作的。 newIndex 的项目将如何处理？我的假设是 index> = newIndex 的每个项目的索引都会减少。这个假设正确吗？更重要的是，该行为是在MSDN上的某个地方解释还是描述的？

I don't understand how it works. What happens to the item with newIndex? My assumption is that the index of each item with index >= newIndex is decremented. Is that assumption correct? And more importantly, is that behavior explained or described somewhere on MSDN?

推荐答案

让我解释一下以单元测试的形式移动：

[Test]
public void ObservableTest()
{
    var observable = new ObservableCollection<string> { "A", "B", "C", "D", "E" }; 

    observable.Move(1, 3); // oldIndex < newIndex 
    // Move "B" to "D"'s place: "C" and "D" are shifted left
    CollectionAssert.AreEqual(new[] { "A", "C", "D", "B", "E" }, observable);

    observable.Move(3, 1); // oldIndex > newIndex 
    // Move "B" to "C"'s place: "C" and "D" are shifted right
    CollectionAssert.AreEqual(new[] { "A", "B", "C", "D", "E" }, observable);

    observable.Move(1, 1); // oldIndex = newIndex
    // Move "B" to "B"'s place: "nothing" happens
    CollectionAssert.AreEqual(new[] { "A", "B", "C", "D", "E" }, observable);
}

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