在c#中删除listBoxItem时ListBox不刷新

Posted 2023-04-12

【中文标题】在c#中删除listBoxItem时ListBox不刷新

【英文标题】：ListBox doesn't refresh when listBoxItem is deleted in c#

【发布时间】：2018-01-09 17:56:43

【问题描述】：

从 ListBox 中删除列表框项时如何刷新 UserInterface。ListBoxItem 正在从数据库中删除，但列表框未刷新。当我按下后退按钮并导航到它被删除的页面时。谁能告诉我如何刷新列表框。我认为这是由于可观察的集合，我不知道如何实现此代码更改的 NotifyProperty。有人可以帮我吗？

用于从数据库中插入、读取和删除项目的 C# 代码

 public class DatabaseHelperClass


    SQLiteConnection dbConn;

    //Create Tabble 
    public async Task<bool> onCreate(string DB_PATH)
    
        try
        
            if (!CheckFileExists(DB_PATH).Result)
            
                using (dbConn = new SQLiteConnection(DB_PATH))
                
                    dbConn.CreateTable<Data>();
                
            
            return true;
        
        catch
        
            return false;
        
    
    private async Task<bool> CheckFileExists(string fileName)
    
        try
        
            var store = await Windows.Storage.ApplicationData.Current.LocalFolder.GetFileAsync(fileName);
            return true;
        
        catch (NullReferenceException exp)
        
            return false;
        
        catch (Exception ex)
        
            return false;
        
    

    // Retrieve the specific contact from the database. 
    public Data ReadContact(int contactid)
    
        using (var dbConn = new SQLiteConnection(App.DB_PATH))
        
            var existingconact = dbConn.Query<Data>("select * from Contacts where Id =" + contactid).FirstOrDefault();
            return existingconact;
        
    
    // Retrieve the all contact list from the database. 
    public ObservableCollection<Data> ReadContacts()
    
        using (var dbConn = new SQLiteConnection(App.DB_PATH))
        
            List<Data> myCollection = dbConn.Table<Data>().ToList<Data>();
            ObservableCollection<Data> ContactsList = new ObservableCollection<Data>(myCollection);

            return ContactsList;
        




    // Insert the new contact in the Contacts table. 
    public void Insert(Data newcontact)
    
        using (var dbConn = new SQLiteConnection(App.DB_PATH))
        
            dbConn.RunInTransaction(() =>
            
                dbConn.Insert(newcontact);
            );
        
    

    //Delete specific contact 
    public void DeleteContact(int Id)
    
         using (var dbConn = new SQLiteConnection(App.DB_PATH))
        
            var existingconact = dbConn.Query<Data>("select * from Data where Id =" + Id).FirstOrDefault();
            if (existingconact != null)
            
                dbConn.RunInTransaction(() =>
                
                    dbConn.Delete(existingconact);
                );
            
        
    
    //Delete all contactlist or delete Contacts table 
    public void DeleteAllContact()
    
        using (var dbConn = new SQLiteConnection(App.DB_PATH))
        
            //dbConn.RunInTransaction(() => 
            //    
            dbConn.DropTable<Data>();
            dbConn.CreateTable<Data>();
            dbConn.Dispose();
            dbConn.Close();
            //); 
        
    

从列表中删除项目的代码。

 public partial class Panaroma : Page

    ObservableCollection<Data> DB_ContactList = new ObservableCollection<Data>();


    public Panaroma()
    
        this.InitializeComponent();
        if(listBoxobj.Items.Count == 0)
        
            Btn_Delete.IsEnabled = false;
        


        this.Loaded += Panaroma_Loaded;

    

    private void Panaroma_Loaded(object sender, RoutedEventArgs e)
    
        ReadAllData dbcontacts = new ReadAllData();

        DB_ContactList = dbcontacts.GetAllContacts();//Get all DB contacts 
        if (DB_ContactList.Count > 0)
        
            Btn_Delete.IsEnabled = true;
        
        listBoxobj.ItemsSource = DB_ContactList.OrderByDescending(i => i.Id).ToList();//Binding DB data to LISTBOX and Latest contact ID can Display first.

    


    private void listBoxobj_SelectionChanged(object sender, SelectionChangedEventArgs e)
    
        int SelectedContactID = 0;
        if (listBoxobj.SelectedIndex != -1)
        
            Data listitem = listBoxobj.SelectedItem as Data;//Get slected listbox item 
            DatabaseHelperClass Db_Helper = new DatabaseHelperClass();
            Db_Helper.DeleteContact(listitem.Id);//Delete selected DB contact Id.
        
    

【问题讨论】：

您只是从数据库中删除选定的项目。此外，您应该从集合中删除它并刷新集合。对于 INotifyPropertyChanged 接口的实现，这里有一些很好的例子。

嗨@Ben，如何从集合中删除所选项目？

【参考方案1】：

要从集合中删除项目，请使用方法Remove (listitem) msdn 并更新相关的列表框。

private void listBoxobj_SelectionChanged(object sender, SelectionChangedEventArgs e)

    int SelectedContactID = 0;
    if (listBoxobj.SelectedIndex != -1)
    
        Data listitem = listBoxobj.SelectedItem as Data;//Get slected listbox item 
        DatabaseHelperClass Db_Helper = new DatabaseHelperClass();
        Db_Helper.DeleteContact(listitem.Id);//Delete selected DB contact Id.
        //remove item from collection
        DB_ContactList.Remove(listitem); 
        //update listbox
        //...
    

要更新列表框，请查看post