patcher/Patcher/PatchGenerator/CustomControls/FolderSelector.axaml.cs

using Avalonia;
using Avalonia.Controls;
using Avalonia.Input;
using Avalonia.Markup.Xaml;
using System.IO;
using System.Linq;

namespace PatchGenerator.CustomControls
{
    public partial class FolderSelector : UserControl
    {
        public FolderSelector()
        {
            InitializeComponent();

            AddHandler(DragDrop.DropEvent, Drop);
        }

        private void InitializeComponent()
        {
            AvaloniaXamlLoader.Load(this);
        }

        private void Drop(object sender, DragEventArgs e)
        {
            if (e.Data.Contains(DataFormats.FileNames))
            {
                string[] filePaths = e.Data.GetFileNames().ToArray();

                if (filePaths.Length == 1)
                {
                    DirectoryInfo folder = new DirectoryInfo(filePaths[0]);

                    if (folder.Exists)
                    {
                        FolderPath = filePaths[0];
                        FolderSelected = true;
                        return;
                    }

                    FolderPath = "Dropped object must be a folder";
                    FolderSelected = false;
                    return;
                }

                FolderPath = "Cannot drop multiple files";
                FolderSelected = false;
            }
        }

        private static readonly StyledProperty<bool> FolderSelectedProperty =
            AvaloniaProperty.Register<FolderSelector, bool>(nameof(FolderSelected));

        private bool FolderSelected
        {
            get => GetValue(FolderSelectedProperty);
            set => SetValue(FolderSelectedProperty, value);
        }

        public static readonly StyledProperty<string> FolderPathProperty =
            AvaloniaProperty.Register<FolderSelector, string>(nameof(FolderPath));

        public string FolderPath
        {
            get => GetValue(FolderPathProperty);
            set => SetValue(FolderPathProperty, value);
        }
    }
}