MainWindow.xaml.cs

using System;
using System.Text.RegularExpressions;
using System.Threading;
using System.Windows;
using System.Windows.Input;
using NHotkey;
using NHotkey.Wpf;

namespace AutoClicker;

/// <summary>Interaction logic for MainWindow.xaml</summary>
public partial class MainWindow
{
    private Timer? _timer;

    public MainWindow()
    {
        HotkeyManager.Current.AddOrReplace("ToggleAutoClick", Key.F8, ModifierKeys.None, HotkeyAutoClicker);
        InitializeComponent();
    }

    private void HotkeyAutoClicker(object? sender, HotkeyEventArgs e) =>
        ToggleButtonAutoClick.IsChecked = ToggleButtonAutoClick.IsChecked != true;

    private void ToggleButtonAutoClick_Checked(object sender, RoutedEventArgs e)
    {
        if (!int.TryParse(TextBoxInterval.Text, out int interval) || interval < 1)
        {
            TextBoxInterval.Text = "1";
            interval             = 1;
        }
        var period = TimeSpan.FromMilliseconds(interval);

        _timer = new(_ => MouseOperations.Event(MouseOperations.EventFlag.Click), null, TimeSpan.Zero, period);
    }

    private void ToggleButtonAutoClick_UnChecked(object sender, RoutedEventArgs e) => _timer?.Dispose();

    private void TextBoxInterval_OnPreviewTextInput(object sender, TextCompositionEventArgs e) =>
        e.Handled = !Regex.IsMatch(e.Text, @"\d+");
}