={Binding Months}3:SelectedItem
={Binding Month, Mode=TwoWay}/ 似乎可行，但如果是默認加載第壹項的話，這個SelectedItem就應該是綁定源更新以後的ItemSource.FirstOrDefault()，為何要雙向綁定呢?有壹點不太爽。有沒有其它辦法呢?很簡單，繼承ComboBox，寫壹個控件，讓它默認選中第壹項，就解決這個問題了，不用綁定SelectedItem。
<ComboBoxItemsSource
={Binding Months}/ 自定義ComboBox控件代碼如下，也非常簡單，思路就是ItemSource更新以後就自動默認選中第壹行即可：1:publicclassCustomComboBox : ComboBox2:{3:/// <summary4:/// Initializes a new instance of the <see cref=CustomComboBox/ class.5:/// </summary6:publicCustomComboBox()7:{8:Loaded += ComboBoxLoaded;9:SelectionChanged += ComboBoxSelectionChanged;10:}11:12:voidComboBoxLoaded(objectsender, RoutedEventArgs e)13:{14:SetSelectedItem();15:}16:17:voidComboBoxSelectionChanged(objectsender, SelectionChangedEventArgs e)18:{19:SelectedItem = e.AddedItems.Count 0 ? e.AddedItems[0] :null;20:}21:22:publicnewobjectSelectedItem23:{24:get {return(object)GetValue(SelectedItemProperty); }25:set { SetValue(SelectedItemProperty,
value); }26:}27:28:publicnewstaticreadonlyDependencyProperty SelectedItemProperty =29:DependencyProperty.Register(
SelectedItem,
typeof(object),
typeof(CustomComboBox),
30:newPropertyMetadata((o, e) = ((CustomComboBox)o).SetSelectedItem()));31:32:privatevoidSetSelectedItem()33:{34:if(Items.Count 0)35:base
.SelectedIndex = 0;36:37://var value = SelectedItem;38://if (Items.Count 0 && value != null)39://{40:// base.SelectedIndex = Items.IndexOf(value);41://}42:}43:44:protectedoverridevoidOnItemsChanged(System.Collections.Specialized.NotifyCollectionChangedEventArgs e)45:{46:base
.OnItemsChanged(e);47:SetSelectedItem();48:}49:} 如果妳覺得代碼好用就拿過去，否則請分享更好的代碼。