值的列表中沒有重複（C＃）

Question

我創建了一個最愛列表框，用戶可以從Textblock在MainPage.xaml

<StackPanel Grid.Row="0" Grid.Column= "0" HorizontalAlignment= "Left" VerticalAlignment= "Top" > 
    < Button x:Name= "FavoriteButton" FontFamily= "Segoe MDL2 Assets" 
      Content= "&#xE006;" BorderBrush= "Transparent" FontSize= "28" 
      Foreground= "{StaticResource PhoneForegroundBrush}" 
      Style= "{StaticResource ButtonStyle1}" Click= "FavoriteButton_Click" /> 
</ StackPanel > 

<StackPanel Grid.Row="0" Grid.Column= "2" HorizontalAlignment= "Left" VerticalAlignment= "Top" > 
    < Button x:Name= "FavoriteListButton" FontFamily= "Segoe MDL2 Assets" 
      Content= "&#xEA55;" BorderBrush= "Transparent" FontSize= "28" 
      Foreground= "{StaticResource PhoneForegroundBrush}" 
      Style= "{StaticResource ButtonStyle1}" Click= "FavoriteListButton_Click" /> 
</ StackPanel > 

C#

private void FavoriteButton_Click(object sender, RoutedEventArgs e) 
    { 

     listobj.Add(new MyData { AnswerName = AnswerTextBlock.Text }); 


     using (IsolatedStorageFileStream fileStream = Settings1.OpenFile("MyStoreItems", FileMode.Create)) 
     { 
      DataContractSerializer serializer = new DataContractSerializer(typeof(MyDataList)); 
      serializer.WriteObject(fileStream, listobj); 

     } 
    } 

    private void FavoriteListButton_Click(object sender, RoutedEventArgs e) 
    { 
     if(FavoriteListBox.Visibility.Equals(Visibility.Collapsed)) 
     { 
      FavoriteListBox.Visibility = Visibility.Visible; 
     } 
     else if(FavoriteListBox.Visibility.Equals(Visibility.Visible)) 
     { 
      FavoriteListBox.Visibility = Visibility.Collapsed; 
     }   
    } 

和列表框

XAML保存文本

 <StackPanel Grid.Column="1" Grid.Row="0" HorizontalAlignment="Center" VerticalAlignment="Top">     
      <ListBox x:Name="FavoriteListBox" Visibility="Collapsed" 
        SelectionChanged="FavoriteListBox_SelectionChanged" 
        HorizontalAlignment="Stretch" 
        VerticalAlignment="Top" Opacity="1" 
        Background="{StaticResource PhoneBackgroundBrush}" Foreground="{StaticResource PhoneForegroundBrush}" 
        Height="300" Width="250"> 
       <ListBox.ItemTemplate> 
        <DataTemplate> 
         <TextBlock Visibility="Visible" x:Name="FavoriteListBoxTextBlock" 
            FontSize="35" Foreground="Black" Text="{Binding AnswerName}"/> 
        </DataTemplate> 
       </ListBox.ItemTemplate> 
      </ListBox> 
     </StackPanel> 

C#

public partial class MainPage : PhoneApplicationPage 
{ 
    IsolatedStorageFile Settings1 = IsolatedStorageFile.GetUserStoreForApplication(); 
    MyDataList listobj = new MyDataList(); 

    public MainPage() 

    { 
     InitializeComponent(); 

     this.Loaded += MainPage_Loaded; 

     if (Settings1.FileExists("MyStoreItems")) 
     { 
      using (IsolatedStorageFileStream fileStream = Settings1.OpenFile("MyStoreItems", FileMode.Open)) 
      { 
       DataContractSerializer serializer = new DataContractSerializer(typeof(MyDataList)); 
       listobj = (MyDataList)serializer.ReadObject(fileStream); 

      } 
     } 


     FavoriteListBox.ItemsSource = listobj;//binding isolated storage list data 



    private void MainPage_Loaded(object sender, RoutedEventArgs e) 
    { 
     if (Settings1.FileExists("MyStoreItems"))//loaded previous items into list 
     { 
      using (IsolatedStorageFileStream fileStream = Settings1.OpenFile("MyStoreItems", FileMode.Open)) 
      { 
       DataContractSerializer serializer = new DataContractSerializer(typeof(MyDataList)); 
       listobj = (MyDataList)serializer.ReadObject(fileStream); 

      } 
     } 
    } 

    public class MyData 
    { 
     public string AnswerName { get; set; }    
    } 
    public class MyDataList : ObservableCollection<MyData> //for storing mydata class items with type of list 
    { 

    } 

的Textbox所有文字，其表現出一定的文字去的收藏夾按鈕點擊獨立存儲。但它再次複製相同的文本，即使該文本已經存在於列表中，所以我希望當用戶點擊最喜歡的按鈕時，它應該首先檢查文本是否已經存在於列表中，如果存在，則它應該替換或不應該複製再次。所以如何做到這一點。

Answer 1

您可以重複檢查很容易地使用LINQ Any查詢在FavoriteButton_Click方法的開頭：

private void FavoriteButton_Click(object sender, RoutedEventArgs e) 
{ 
    //check if there is any item with the same text 
    //in which case do not continue 
    if (listobj.Any(l => l.AnswerName == AnswerTextBlock.Text)) return; 

    listobj.Add(new MyData { AnswerName = AnswerTextBlock.Text }); 


    using (IsolatedStorageFileStream fileStream = Settings1.OpenFile("MyStoreItems", FileMode.Create)) 
    { 
     DataContractSerializer serializer = new DataContractSerializer(typeof(MyDataList)); 
     serializer.WriteObject(fileStream, listobj); 

    } 
}