This is a list of common LINQ mistakes, which has grown out from reading code of others (and myself) - and using the results for training people new to .NET. 

I've always said that when a new version of something comes out, you should always "let the scouts take the arrows." Basically, let the testers see if everything is ok before giving the go-ahead to start using it. 

        private async Task<List<System.Windows.Media.Imaging.BitmapImage>> getPdfPageImages()
        {
            var results = new List<System.Windows.Media.Imaging.BitmapImage>();
            using (var randomAccessStream = File.Open("PieChartPdfReport.pdf", FileMode.Open).AsRandomAccessStream())
            {
                var pdfDocument = await PdfDocument.LoadFromStreamAsync(randomAccessStream);
                for (uint i = 0; i < pdfDocument.PageCount; i++)
                {
                    using (var memoryStream = new MemoryStream())
                    {
                        using (var stream = memoryStream.AsRandomAccessStream())
                        {
                            using (var page = pdfDocument.GetPage(i))
                            {
                                // Set render options
                                var renderOptions = new PdfPageRenderOptions
                                {
                                    BackgroundColor = Colors.LightGray,
                                    DestinationHeight = (uint)(page.Size.Height * 10)
                                };

                                await page.RenderToStreamAsync(stream); //, renderOptions);
                                await stream.FlushAsync();

                                var bitmapImage = new System.Windows.Media.Imaging.BitmapImage();
                                bitmapImage.BeginInit();
                                //Without this, BitmapImage uses lazy initialization by default and the stream will be closed by then.
                                bitmapImage.CacheOption = System.Windows.Media.Imaging.BitmapCacheOption.OnLoad;
                                bitmapImage.StreamSource = memoryStream;
                                bitmapImage.EndInit();

                                results.Add(bitmapImage);
                            }
                        }
                    }
                }
            }
            return results;
        }

        private async void Button_Click(object sender, RoutedEventArgs e)
        {
            var images = await this.getPdfPageImages();
            ImagePdf.Source = images.First();
        }

using System.Web.Mvc;

namespace TestMvcPRG.Helper
{
    public class Redirect303 : ActionResult
    {
        private string _url;

        public Redirect303(string url)
        {
            _url = url;
        }

        public override void ExecuteResult(ControllerContext context)
        {
            context.HttpContext.Response.StatusCode = 303; // redirect using GET
            context.HttpContext.Response.RedirectLocation = _url;
        }
    }

    public abstract class BaseController : Controller
    {
        public Redirect303 Redirect303(string actionName)
        {
            return new Redirect303(Url.Action(actionName));
        }

        public Redirect303 Redirect303(string actionName, object routeValues)
        {
            return new Redirect303(Url.Action(actionName, routeValues));
        }

        public Redirect303 Redirect303(string actionName, string controllerName)
        {
            return new Redirect303(Url.Action(actionName, controllerName));
        }

        public Redirect303 Redirect303(string actionName, string controllerName, object routeValues)
        {
            return new Redirect303(Url.Action(actionName, controllerName, routeValues));
        }
    }
}

using System.Web.Mvc;
using TestMvcRPG.Helper;

namespace TestMvcPRG.Controllers
{
    public class HomeController : BaseController
    {
        [HttpGet]
        public ActionResult Index()
        {
            return View();
        }

        [HttpPost]
        public ActionResult Index(string data)
        {
            if (ModelState.IsValid)
            {
                return Redirect303("Index"); // post-redirect-get
            }
            return View();
        }
    }
}

@using System.IO;
@{
    var pathsplited = new string[] { };
    if (ViewBag.CurrentPath != null)
    {
        pathsplited = ViewBag.CurrentPath.Split(Path.DirectorySeparatorChar);
    }
    string Host = Request.Url.Authority + "/" + MvcFileManager.Services.Helper.PathBrowseinWebConfig;
    string pathcombine = "";
}
@Html.ActionLink(Host , "Browse", new { path = pathcombine })  /

@if (pathsplited != null)
{
    foreach (var s in pathsplited)
    {
        if (s != "")
        {
            pathcombine += s + @"\";
            @Html.ActionLink(s, "Browse", new { path = pathcombine })
            @Html.Raw(" / ")   ;
        }

    }
}

@using System.Diagnostics
@using MvcFileManager.Services
@{
    var pathsplited = new string[] { };
    if (ViewBag.CurrentPath != null)
    {
        pathsplited = ViewBag.CurrentPath.Split(Path.DirectorySeparatorChar);
    }

    Debug.Assert(Request.Url != null, "Request.Url != null");
    string host = Request.Url.Authority + "/" + Helper.PathBrowseinWebConfig;
    string pathcombine = "";
}
@Html.ActionLink(host , "Browse", new { path = pathcombine })  

@if (pathsplited != null)
{
    foreach (var s in pathsplited)
    {
        if (s.Trim() != "")
        {
            @Html.Raw(" / ")
            pathcombine += s;
            pathcombine += Helper.FileFolderCheck(pathcombine) == FileFolderStatus.File ? "" : @"\";
            @Html.ActionLink(s, "Browse", new { path = pathcombine })
        }
    }
    @Html.Raw(Helper.FileFolderCheck(ViewBag.CurrentPath)==FileFolderStatus.File ? "" : (" / "))
}