Remove an item from listbox in WP8

Question

I'm new to windows phone development. I'm trying to delete selected item from the list box. I've got dataclass

public class MyDataClass 
{ 
    public string MSG { get; set; } 
    public int Id { get; set; } 
}

Then I try to delete the selected item (Button1_Click event)

MyDataClass item = MyDict.SelectedItem as MyDataClass; 
ObservableCollection dataList = new ObservableCollection(); 
dataList.Remove(item);

The problem in creating the datalist in task, so it's no availble for the rest of the program, how to change this?

    public async Task GETFROMDB()
    {
        int a = 1;
        Database database = new Database(ApplicationData.Current.LocalFolder, "DictData.db");
        await database.OpenAsync();
        string query = "SELECT * FROM MyDICT";
        Statement statement = await database.PrepareStatementAsync(query);
        statement.EnableColumnsProperty();
        ObservableCollection<MyDataClass> dataList = new ObservableCollection<MyDataClass>();
        while (await statement.StepAsync())
        {
            rawData = string.Format(statement.Columns["value"]);
            string[] sep = new string[] { "\r\n" }; //Splittng it with new line
            string[] arrData = rawData.Split(sep, StringSplitOptions.RemoveEmptyEntries);
            foreach (var d in arrData)
            {
                dataList.Add(new MyDataClass() { MSG = d, Id= a });
                a++;
            }
        }
        MyDict.ItemsSource = dataList;
    }

Answer 1

Can you make binding to a dataList outside the Task and make dataList static or reference to it in a Task?

When creating a list:

static ObservableCollection<MyDataClass> dataList = new ObservableCollection<MyDataClass>(); 
MyDict.ItemsSource = dataList;

Then in Task:

public async Task GETFROMDB()
{
    int a = 1;
    Database database = new Database(ApplicationData.Current.LocalFolder, "DictData.db");
    await database.OpenAsync();
    string query = "SELECT * FROM MyDICT";
    Statement statement = await database.PrepareStatementAsync(query);
    statement.EnableColumnsProperty();
    while (await statement.StepAsync())
    {
        rawData = string.Format(statement.Columns["value"]);
        string[] sep = new string[] { "\r\n" }; //Splittng it with new line
        string[] arrData = rawData.Split(sep, StringSplitOptions.RemoveEmptyEntries);
        foreach (var d in arrData)
        {
            dataList.Add(new MyDataClass() { MSG = d, Id= a });
            a++;
        }
    }
}

Then in Click:

MyDataClass item = MyDict.SelectedItem as MyDataClass; 
dataList.Remove(item);

Or make it:

When creating a list:

ObservableCollection<MyDataClass> dataList = new ObservableCollection<MyDataClass>(); 
MyDict.ItemsSource = dataList;

Then in Task:

public async Task GETFROMDB(ObservableCollection<MyDataClass> dataList)
{
    int a = 1;
    Database database = new Database(ApplicationData.Current.LocalFolder, "DictData.db");
    await database.OpenAsync();
    string query = "SELECT * FROM MyDICT";
    Statement statement = await database.PrepareStatementAsync(query);
    statement.EnableColumnsProperty();
    while (await statement.StepAsync())
    {
        rawData = string.Format(statement.Columns["value"]);
        string[] sep = new string[] { "\r\n" }; //Splittng it with new line
        string[] arrData = rawData.Split(sep, StringSplitOptions.RemoveEmptyEntries);
        foreach (var d in arrData)
        {
            dataList.Add(new MyDataClass() { MSG = d, Id= a });
            a++;
        }
    }
}

Then in Click:

 MyDataClass item = MyDict.SelectedItem as MyDataClass; 
 dataList.Remove(item);

Of course you need to wait until the Task is finished.

Answer 2

you appear to be trying to remove the item from a brand new collection - try instead to remove it from the one that your listbox is data bound to.

Answer 3

Try using the button data context

like this

in your click handler

      private void ButtonClick(object sender, RoutedEventArgs e)
      {
         Button btn = sender as Button;
         if (btn != null)
          {
             MyDataClass item = btn.DataContext as MyDataClass; 
             dataList.Remove(item);
          }

        }