Active Directory图形客户端:使用c# API删除应用程序

下面有一个调用导致我的程序终止。请告诉我为什么。

        TaskCompletionSource<string> tcs = new TaskCompletionSource<string>();
        tcs.SetResult(accessToken);
        ActiveDirectoryClient graphClient = new ActiveDirectoryClient(
            new Uri($"https://graph.windows.net/{tenantId}"),
            async () => { return await tcs.Task; });
// this part runs fine and I can see a list of applications being printed
        foreach (var app in graphClient.Applications.ExecuteAsync().Result.CurrentPage)
        {
            Console.WriteLine($"{app.AppId}, {app.DisplayName}");
        }
// this call causes the program to terminate 
        var matches = await graphClient.Applications
            .Where(app => app.AppId == clientId)
            .ExecuteAsync();
// the execution never gets to this part:
        foreach (IApplication app in matches.CurrentPage.ToList())
        {
            await app.DeleteAsync();
        }