ComboBox SelectionChanged事件火災晚

Question

在我的WPF應用程序中，我有一個ComboBox，用於爲AutoCompletebox選擇ItemFilter。下面是代碼：

XAML

<ComboBox 
    Name="SearchFilter" 
    HorizontalAlignment="Right" 
    MinWidth="75" Margin="0,3,0,3" 
    SelectionChanged="SearchFilter_SelectionChanged"> 
      <ComboBoxItem>Full-Time</ComboBoxItem> 
      <ComboBoxItem>Part-Time</ComboBoxItem> 
      <ComboBoxItem>Retired</ComboBoxItem> 
      <ComboBoxItem>Stockholder</ComboBoxItem> 
      <ComboBoxItem>Terminated</ComboBoxItem> 
      <ComboBoxItem>None</ComboBoxItem> 
</ComboBox> 

C＃

private void SearchFilter_SelectionChanged(object sender, SelectionChangedEventArgs e) 
    { 
     if (SearchFilter.SelectedItem != null) 
     { 
      if (SearchFilter.Text == "Full-Time") 
      { 
       EmployeeAutoBox.ItemFilter = PersonFilter_Full; 
      } 
      else if (SearchFilter.Text == "Part-Time") 
      { 
       EmployeeAutoBox.ItemFilter = PersonFilter_Part; 
      } 
      else if (SearchFilter.Text == "Retired") 
      { 
       EmployeeAutoBox.ItemFilter = PersonFilter_Ret; 
      } 
      else if (SearchFilter.Text == "Stockholder") 
      { 
       EmployeeAutoBox.ItemFilter = PersonFilter_Stock; 
      } 
      else if (SearchFilter.Text == "Terminated") 
      { 
       EmployeeAutoBox.ItemFilter = PersonFilter_Term; 
      } 
      else 
      { 
       EmployeeAutoBox.ItemFilter = PersonFilter; 
      } 
     } 
    } 

出於某種原因，經過予改變的所選被改變正在應用的過濾器。例如，我將組合框設置爲「全職」，列表篩選器未應用。然後，我將ComboBox設置爲「Part-Time，全時間過濾器正在應用，然後我將ComboBox設置爲」Retired「，Part Time過濾器正在應用等等等等......我已經使用了ComboBox for類似的東西之前，它通常基於目前在框中的東西，而不是在框中是什麼。我在這裏缺少什麼？

Answer 1

Text只是關於SearchFilter的唯一財產，將不會被更新。您的SelectionChanged處理程序（不要問我爲什麼不）

SelectedItem會好的，SelectedValue將是很好的（在你的情況下，兩者都將被選定ComboBoxItem - 不使用WPF的好方法，但我米不是你的牧師），和SelectedIndex。

我們將對XAML進行一個小改動（見下文），以便我們可以從SelectedValue中獲取所選字符串。

private void SearchFilter_SelectionChanged(object sender, SelectionChangedEventArgs e) 
{ 
    // Not sure there's any reason for this null check. 
    if (SearchFilter.SelectedValue != null) 
    { 
     var filter = SearchFilter.SelectedValue as String; 

     switch (filter) 
     { 
      case "Full-Time": 
       EmployeeAutoBox.ItemFilter = PersonFilter_Full; 
       break; 
      case "Part-Time": 
       EmployeeAutoBox.ItemFilter = PersonFilter_Part; 
       break; 
      case "Retired": 
       EmployeeAutoBox.ItemFilter = PersonFilter_Ret; 
       break; 
      case "Stockholder": 
       EmployeeAutoBox.ItemFilter = PersonFilter_Stock; 
       break; 
      case "Terminated": 
       EmployeeAutoBox.ItemFilter = PersonFilter_Term; 
       break; 
      default: 
       EmployeeAutoBox.ItemFilter = PersonFilter; 
       break; 
     } 
    } 
} 

XAML：除了縮進的唯一變化是增加的SelectedValuePath="Content"屬性。所做的是，當選擇發生變化時（並在事件發生之前），ComboBox現在將查看SelectedItem中的對象，無論它是什麼，並查找名爲「Content」的屬性。如果它發現，它將使用SelectedItem的Content屬性的值爲SelectedValue。你給這些的內容是字符串：「兼職」等等所以然後

<ComboBox 
    Name="SearchFilter" 
    SelectedValuePath="Content" 
    HorizontalAlignment="Right" 
    MinWidth="75" 
    Margin="0,3,0,3" 
    SelectionChanged="SearchFilter_SelectionChanged" 
    > 
    <ComboBoxItem Tag="Full-Time">Full-Time</ComboBoxItem> 
    <ComboBoxItem>Part-Time</ComboBoxItem> 
    <ComboBoxItem>Retired</ComboBoxItem> 
    <ComboBoxItem>Stockholder</ComboBoxItem> 
    <ComboBoxItem>Terminated</ComboBoxItem> 
    <ComboBoxItem>None</ComboBoxItem> 
</ComboBox>