如何从另一个 void c# 获得 object

Question

I want to change item.header from the Timer_Elapsed method. How can I acheive it? This is my code:

namespace Oceansurfer
{
    public sealed partial class MainPage : Page
    {
        public MainPage()
        {
            this.InitializeComponent();
            System.Timers.Timer timer = new System.Timers.Timer();
            timer.Interval = 5000;
            timer.AutoReset = true;
            timer.Elapsed += Timer_Elapsed;
            timer.Start();
        }

        public void TabView_Loaded(object sender, RoutedEventArgs e)
        {
            TabViewItem item = CreateNewTab(1);
            item.Header = Shared.FileHelper.ReadTitleFromFile();
            (sender as TabView).TabItems.Add(item);
        }
        public void Timer_Elapsed(object sender, ElapsedEventArgs e)
        {    
        }
    }
}

Please, if you can answer this, I will be very grateful.

Answer 1

You can define a private member, in this case, all methods of the current class to access this item or you can use the TabItems of TabView to get the latest item. In addition, if you want to change the Header of TabeViewItem in Timer_Elapsed method, since the timer is used with worker threads and the UI needs to be updated in the UI thread, you need to use Dispatcher.RunAsync method to back to the UI thread.

private TabViewItem currentItem;

public async void Timer_Elapsed(object sender, ElapsedEventArgs e)
{
    await Dispatcher.RunAsync(CoreDispatcherPriority.Normal, () =>
    {
        //TabViewItem item = Tabs.TabItems[Tabs.TabItems.Count-1] as TabViewItem;
        currentItem.Header = "hello2";
    });

}

private void Tabs_Loaded(object sender, RoutedEventArgs e)
{
    TabViewItem item = CreateNewTab(1);
    item.Header = Shared.FileHelper.ReadTitleFromFile();
    (sender as TabView).TabItems.Add(item);
    currentItem = item;
}

Answer 2

You cannot access the local variables of one method from within another method. However, there are multiple ways to access the same object in different methods. The procedural way would be to return it as the result of one method and/or pass it as a parameter to another method. The object oriented (and recommended) way is, when the methods are all part of the same class, make a field (or property) for the object you want to access in multiple methods.