ObservableCollection <T> .Move(int,int)如何工作？

Question

我似乎无法通过阅读MSDN上的ObservableCollection.Move(int oldIndex,int newIndex)的文档来解决这个问题:

oldIndex类型:System.Int32从零开始的索引,指定要移动的项的位置.newIndex类型:System.Int32从零开始的索引,指定项的新位置.

我不明白它是如何工作的.该项目会发生什么变化newIndex？我的假设是每个项目的索引index >= newIndex递减.这个假设是否正确？更重要的是,在MSDN上某处解释或描述了这种行为？

Answer 1

让我Move以单元测试的形式解释一下行为:

[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);
}