ComboBox- SelectionChanged事件具有旧值，而不是新值 [英] ComboBox- SelectionChanged event has old value, not new value

问题描述

C＃、. NET 4.0，VS2010。

C#, .NET 4.0, VS2010.

WPF的新功能。我的MainWindow上有一个ComboBox。我迷上了所述组合框的SelectionChanged事件。但是，如果我在事件处理程序中检查组合框的值，则它具有旧值。这听起来更像是 SelectionChanging事件，而不是SelectionChanged事件。

New to WPF. I have a ComboBox on my MainWindow. I hooked the SelectionChanged event of said combo box. However, if I examine the value of the combo box in the event handler, it has the old value. This sounds more like a "SelectionChanging" event, than a SelectionChanged event.

选择实际发生后，如何获得ComboBox的新值？

How do I get the new value of the ComboBox after the selection has actually happend?

当前：

this.MyComboBox.SelectionChanged += new SelectionChangedEventHandler(OnMyComboBoxChanged);

...
private void OnMyComboBoxChanged(object sender, SelectionChangedEventArgs e)
{
    string text = this.MyComboBox.Text;
}

注意，如果我使用在事件参数，例如e.OriginalSource。

Note, I get the same behaviour if I use the object being passed in the event args, e.g. e.OriginalSource.

推荐答案

根据MSDN， e.AddedItems ：

According to MSDN, e.AddedItems:

获取包含所选项目的列表。

Gets a list that contains the items that were selected.

因此您可以使用：

private void OnMyComboBoxChanged(object sender, SelectionChangedEventArgs e)
{
    string text = (e.AddedItems[0] as ComboBoxItem).Content as string;
}

您也可以使用 SelectedItem 如果您将字符串值用于发件人物品 c>：

You could also use SelectedItem if you use string values for the Items from the sender:

private void OnMyComboBoxChanged(object sender, SelectionChangedEventArgs e)
{
    string text = (sender as ComboBox).SelectedItem as string;
}

或

private void OnMyComboBoxChanged(object sender, SelectionChangedEventArgs e)
{
    string text = ((sender as ComboBox).SelectedItem as ComboBoxItem).Content as string;
}

因为这两个 Content 和 SelectedItem 是对象，更安全的方法是使用 .ToString（）而不是作为字符串

Since both Content and SelectedItem are objects, a safer approach would be to use .ToString() instead of as string

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