(UWP)Events cannot be set in the Application class XAML file hatası

<Page
    x:Class="FinanceManager.MainPage"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    xmlns:local="using:FinanceManager"
    xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
    xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
    mc:Ignorable="d">

    <Grid Background="White" Padding="20">
        <StackPanel>
            <TextBlock Text="Finansal Yönetici" FontSize="24" FontWeight="Bold" HorizontalAlignment="Center"/>
            <TextBox x:Name="IncomeInput" Header="Gelir" PlaceholderText="Gelir girin..." Margin="0,10"/>
            <TextBox x:Name="ExpenseInput" Header="Gider" PlaceholderText="Gider girin..." Margin="0,10"/>
            <DatePicker x:Name="DateInput" Header="Tarih" Margin="0,10"/>
            <Button Content="Ekle" Click="AddTransaction" Margin="0,10"/>
            <ListView x:Name="TransactionsList" Margin="0,10">
                <ListView.ItemTemplate>
                    <DataTemplate>
                        <StackPanel Orientation="Horizontal">
                            <TextBlock Text="{Binding Date}" Width="100"/>
                            <TextBlock Text="{Binding Income}" Width="100"/>
                            <TextBlock Text="{Binding Expense}" Width="100"/>
                        </StackPanel>
                    </DataTemplate>
                </ListView.ItemTemplate>
            </ListView>
            <TextBlock x:Name="TotalIncomeText" Text="Toplam Gelir: 0" Margin="0,10"/>
            <TextBlock x:Name="TotalExpenseText" Text="Toplam Gider: 0" Margin="0,10"/>

using System;
using System.Collections.ObjectModel;
using Windows.UI.Xaml;
using Windows.UI.Xaml.Controls;

namespace FinanceManager
{
    public sealed partial class MainPage : Page
    {
        public ObservableCollection<Transaction> Transactions { get; set; }

        public MainPage()
        {
            this.InitializeComponent();
            Transactions = new ObservableCollection<Transaction>();
            TransactionsList.ItemsSource = Transactions;
        }

        private void AddTransaction(object sender, RoutedEventArgs e)
        {
            double income = 0;
            double expense = 0;

            if (double.TryParse(IncomeInput.Text, out double parsedIncome))
            {
                income = parsedIncome;
            }

            if (double.TryParse(ExpenseInput.Text, out double parsedExpense))
            {
                expense = parsedExpense;
            }

            var transaction = new Transaction
            {
                Date = DateInput.Date.DateTime.ToString("d"),
                Income = income,
                Expense = expense
            };

            Transactions.Add(transaction);

            UpdateTotals();
        }

        private void UpdateTotals()
        {
            double totalIncome = 0;
            double totalExpense = 0;

            foreach (var transaction in Transactions)
            {
                totalIncome += transaction.Income;
                totalExpense += transaction.Expense;
            }

            TotalIncomeText.Text = $"Toplam Gelir: {totalIncome}";
            TotalExpenseText.Text = $"Toplam Gider: {totalExpense}";
            BalanceText.Text = $"Bakiye: {totalIncome - totalExpense}";
        }
    }

    public class Transaction
    {
        public string Date { get; set; }
        public double Income { get; set; }
        public double Expense { get; set; }
    }
}