Install-Package Google.Apis.YouTube.v3
Install-Package Google.Apis.Auth
Install-Package CsvHelper

namespace YouTubeUnsubscriberWpf.Models;
public sealed class SubscriptionItem
{
    public string SubscriptionId { get; set; } = "";
    public string ChannelId { get; set; } = "";
    public string Title { get; set; } = "";
}

using Google.Apis.Auth.OAuth2;
using Google.Apis.Services;
using Google.Apis.YouTube.v3;
using Google.Apis.YouTube.v3.Data;
using System;
using System.Collections.Generic;
using System.IO;
using System.Threading;
using System.Threading.Tasks;
using YouTubeUnsubscriberWpf.Models;
namespace YouTubeUnsubscriberWpf.Services;
public sealed class YouTubeApiClient
{
    private const string AppName = "YouTubeUnsubscriberWpf";
    private static readonly string[] Scopes = { YouTubeService.Scope.Youtube }; // manage account
    private YouTubeService _service;
    public async Task EnsureAuthenticatedAsync(string clientSecretPath, CancellationToken ct)
    {
        if (_service != null) return;
        using var stream = new FileStream(clientSecretPath, FileMode.Open, FileAccess.Read);
        var credential = await GoogleWebAuthorizationBroker.AuthorizeAsync(
            GoogleClientSecrets.FromStream(stream).Secrets,
            Scopes,
            "user",
            ct
        );
        _service = new YouTubeService(new BaseClientService.Initializer
        {
            HttpClientInitializer = credential,
            ApplicationName = AppName
        });
    }
    public async Task<List<SubscriptionItem>> GetMySubscriptionsAsync(CancellationToken ct)
    {
        if (_service == null) throw new InvalidOperationException("Not authenticated.");
        var items = new List<SubscriptionItem>();
        string pageToken = null;
        do
        {
            var req = _service.Subscriptions.List("snippet");
            req.Mine = true;              // mine=true
            req.MaxResults = 50;
            req.PageToken = pageToken;
            SubscriptionListResponse resp = await req.ExecuteAsync(ct);
            foreach (var it in resp.Items)
            {
                items.Add(new SubscriptionItem
                {
                    SubscriptionId = it.Id, // <- isso é o que o delete precisa
                    ChannelId = it.Snippet?.ResourceId?.ChannelId ?? "",
                    Title = it.Snippet?.Title ?? ""
                });
            }
            pageToken = resp.NextPageToken;
        }
        while (!string.IsNullOrEmpty(pageToken));
        return items;
    }
    public async Task DeleteSubscriptionAsync(string subscriptionId, CancellationToken ct)
    {
        if (_service == null) throw new InvalidOperationException("Not authenticated.");
        await _service.Subscriptions.Delete(subscriptionId).ExecuteAsync(ct);
    }
}

<Window x:Class="YouTubeUnsubscriberWpf.MainWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        Title="YouTube Unsubscriber" Height="720" Width="1050">
    <Grid Margin="12">
        <Grid.RowDefinitions>
            <RowDefinition Height="Auto"/>
            <RowDefinition Height="Auto"/>
            <RowDefinition Height="*"/>
            <RowDefinition Height="Auto"/>
        </Grid.RowDefinitions>
        <StackPanel Orientation="Horizontal" Grid.Row="0">
            <Button x:Name="BtnAuth" Content="1) Authenticate" Width="150" Margin="0,0,8,0" Click="BtnAuth_Click"/>
            <Button x:Name="BtnLoad" Content="2) Load Subscriptions" Width="180" Margin="0,0,8,0" Click="BtnLoad_Click" IsEnabled="False"/>
            <Button x:Name="BtnExport" Content="Export CSV" Width="120" Margin="0,0,8,0" Click="BtnExport_Click" IsEnabled="False"/>
            <Button x:Name="BtnUnsub" Content="Unsubscribe ALL" Width="160" Margin="0,0,8,0" Click="BtnUnsub_Click" IsEnabled="False"/>
            <CheckBox x:Name="ChkConfirm" Content="I understand (enable delete)" Margin="12,0,0,0" VerticalAlignment="Center"/>
        </StackPanel>
        <TextBlock x:Name="TxtStatus" Grid.Row="1" Margin="0,10,0,10" Text="Ready." />
        <DataGrid x:Name="GridSubs" Grid.Row="2" AutoGenerateColumns="False" IsReadOnly="True" CanUserAddRows="False">
            <DataGrid.Columns>
                <DataGridTextColumn Header="Title" Binding="{Binding Title}" Width="*"/>
                <DataGridTextColumn Header="ChannelId" Binding="{Binding ChannelId}" Width="320"/>
                <DataGridTextColumn Header="SubscriptionId" Binding="{Binding SubscriptionId}" Width="320"/>
            </DataGrid.Columns>
        </DataGrid>
        <ProgressBar x:Name="Progress" Grid.Row="3" Height="18" Margin="0,12,0,0" Minimum="0" Maximum="100" Value="0"/>
    </Grid>
</Window>

using CsvHelper;
using System;
using System.Collections.Generic;
using System.Globalization;
using System.IO;
using System.Linq;
using System.Threading;
using System.Windows;
using YouTubeUnsubscriberWpf.Models;
using YouTubeUnsubscriberWpf.Services;
namespace YouTubeUnsubscriberWpf;
public partial class MainWindow : Window
{
    private readonly YouTubeApiClient _yt = new();
    private List<SubscriptionItem> _subs = new();
    private readonly CancellationTokenSource _cts = new();
    public MainWindow()
    {
        InitializeComponent();
        Closing += (_, __) => _cts.Cancel();
    }
    private string ClientSecretPath =>
        Path.Combine(AppDomain.CurrentDomain.BaseDirectory, "client_secret.json");
    private async void BtnAuth_Click(object sender, RoutedEventArgs e)
    {
        try
        {
            SetUiBusy(true, "Authenticating...");
            await _yt.EnsureAuthenticatedAsync(ClientSecretPath, _cts.Token);
            TxtStatus.Text = "Authenticated. Now load subscriptions.";
            BtnLoad.IsEnabled = true;
        }
        catch (Exception ex)
        {
            MessageBox.Show(ex.Message, "Auth error", MessageBoxButton.OK, MessageBoxImage.Error);
            TxtStatus.Text = "Auth failed.";
        }
        finally
        {
            SetUiBusy(false);
        }
    }
    private async void BtnLoad_Click(object sender, RoutedEventArgs e)
    {
        try
        {
            SetUiBusy(true, "Loading subscriptions...");
            _subs = await _yt.GetMySubscriptionsAsync(_cts.Token);
            GridSubs.ItemsSource = _subs;
            TxtStatus.Text = $"Loaded: {_subs.Count} subscriptions.";
            BtnExport.IsEnabled = _subs.Count > 0;
            BtnUnsub.IsEnabled = _subs.Count > 0;
        }
        catch (Exception ex)
        {
            MessageBox.Show(ex.Message, "Load error", MessageBoxButton.OK, MessageBoxImage.Error);
            TxtStatus.Text = "Load failed.";
        }
        finally
        {
            SetUiBusy(false);
        }
    }
    private void BtnExport_Click(object sender, RoutedEventArgs e)
    {
        if (_subs.Count == 0)
        {
            MessageBox.Show("No subscriptions loaded.", "Info");
            return;
        }
        var file = Path.Combine(AppDomain.CurrentDomain.BaseDirectory, "subscriptions_backup.csv");
        using var writer = new StreamWriter(file);
        using var csv = new CsvWriter(writer, CultureInfo.InvariantCulture);
        csv.WriteRecords(_subs);
        TxtStatus.Text = $"CSV exported: {file}";
    }
    private async void BtnUnsub_Click(object sender, RoutedEventArgs e)
    {
        if (_subs.Count == 0)
        {
            MessageBox.Show("No subscriptions loaded.", "Info");
            return;
        }
        if (ChkConfirm.IsChecked != true)
        {
            MessageBox.Show("Check 'I understand' to enable deletion.", "Safety");
            return;
        }
        // Always export before delete
        BtnExport_Click(sender, e);
        var confirm = MessageBox.Show(
            $"This will unsubscribe from {_subs.Count} channels.\n\nProceed?",
            "Confirm",
            MessageBoxButton.YesNo,
            MessageBoxImage.Warning);
        if (confirm != MessageBoxResult.Yes) return;
        try
        {
            SetUiBusy(true, "Unsubscribing...");
            Progress.Value = 0;
            int total = _subs.Count;
            int ok = 0, fail = 0;
            var list = _subs.ToList();
            for (int i = 0; i < total; i++)
            {
                var s = list[i];
                TxtStatus.Text = $"[{i + 1}/{total}] Unsubscribing: {s.Title}";
                try { await _yt.DeleteSubscriptionAsync(s.SubscriptionId, _cts.Token); ok++; }
                catch { fail++; }
                Progress.Value = (i + 1) * 100.0 / total;
                await System.Threading.Tasks.Task.Delay(150, _cts.Token);
            }
            TxtStatus.Text = $"Done. Success: {ok}, Failed: {fail}. Reload to confirm.";
        }
        catch (Exception ex)
        {
            MessageBox.Show(ex.Message, "Delete error", MessageBoxButton.OK, MessageBoxImage.Error);
            TxtStatus.Text = "Unsubscribe failed.";
        }
        finally
        {
            SetUiBusy(false);
        }
    }
    private void SetUiBusy(bool busy, string status = null)
    {
        BtnAuth.IsEnabled = !busy;
        if (!string.IsNullOrEmpty(status)) TxtStatus.Text = status;
    }
}