[edit] I want to clarify that the NullReferenceException does not occur within the posted code, but this code somehow gives back null
I'm getting a NullReferenceException when running my application for the first time, and it happens when I access a list as a property. Here is the code:
/// <summary>
/// Gets the list of workouts using Lazy Loading.
/// </summary>
/// <remarks>
/// This is the point of access for Workouts in this Page.
/// </remarks>
public List<WorkoutModel> Workouts
{
get
{
if (workouts == null || !workouts.Any())
{
workouts = JsonFileHelper.LoadWorkouts();
}
return workouts;
}
}
The JsonFileHelper code that is accessed is here:
/// <summary>
/// Retrieves all the workouts from local storage.
/// </summary>
/// <returns>The list of workouts.</returns>
public static List<WorkoutModel> LoadWorkouts()
{
bool couldLoadFile = true;
List<WorkoutModel> workouts = new List<WorkoutModel>();
StorageFolder localFolder = ApplicationData.Current.LocalFolder;
StorageFile textFile = null;
Task<List<WorkoutModel>> t = Task<List<WorkoutModel>>.Run(() => LoadWorkoutsAsync(textFile, localFolder, couldLoadFile));
t.Wait();
workouts = t.Result;
return workouts;
}
Which calls this method on a background thread:
private static async Task<List<WorkoutModel>> LoadWorkoutsAsync(StorageFile textFile, StorageFolder localFolder, bool couldLoadFile)
{
List<WorkoutModel> workouts = new List<WorkoutModel>();
if (localFolder != null)
{
try
{
textFile = await localFolder.GetFileAsync(AppResources.FileName);
}
catch (FileNotFoundException)
{
couldLoadFile = false;
}
if (couldLoadFile)
{
// Create and use a stream to the file atomically
using (IRandomAccessStream textStream = await textFile.OpenReadAsync())
{
// Read the text stream atomically
using (DataReader textReader = new DataReader(textStream))
{
uint length = (uint)textStream.Size;
await textReader.LoadAsync(length);
string data = textReader.ReadString(length);
workouts = JsonConvert.DeserializeObject<List<WorkoutModel>>(data);
}
}
}
}
return workouts;
}
I've noticed that when debugging, the application does not crash - this leads me to believe there is some issue with synchronization going on, because it crashes when the application is run normally. This is my first foray into to asynchronous code, so there's probably something I'm missing.
What could be causing this problem?
Please read the John Saunders question. You need this knowledge, and you should have already found it before posting here.
The code needs to be restructured with variables set predictably on all paths. It's not surprising if you get errors of this kind as it is.
An exception other than FileNotFoundException will leave couldLoadFile as true and textFile as null, triggering this error. This could be your bug.
If this is not enough, then please provide the stack trace.
Instead of using Task.Wait you should try Task.Result.
///
/// Retrieves all the workouts from local storage.
///
/// The list of workouts.
public static List<WorkoutModel> LoadWorkouts()
{
bool couldLoadFile = true;
List<WorkoutModel> workouts = new List<WorkoutModel>();
StorageFolder localFolder = ApplicationData.Current.LocalFolder;
StorageFile textFile = null;
List<WorkoutModel> workouts = Task<List<WorkoutModel>>.Run(() => LoadWorkoutsAsync(textFile, localFolder, couldLoadFile)).Result;
return workouts;
}
Related
This question might be a little ambiguous so I'll explain my goal and my previous implementation. I'm looking for some advice on how to improve my implementation.
My application needs a certain set of days and times (hours and minutes) to be used for criteria later in the program.
The days and times are variable and depend on whether a user is a member of a particular group or not.
My previous implementation was to get the name of the group that was selected and then go to the web server and download the appropriate file which contained the day and time. There was a file for each group.
The format of the text file was:
Day,Day,Day,etc..HH,HH,MM,MM
It was then read into two separate arrays with the positions hardcoded. E.g. Index 0, 1,2 where days while 3,4 where hours and 5,6 where minutes.
This method also meant that I'd need a longer array for a group that had more days than another.
Obviously this was all very inefficient and the code wasn't very reusable or extendable. I'd have to alter if a new group was introduced and it had more of less data in the text file.
Edit - due to the vagueness of the question I have included code:
This method is passed the group name in the fileName parameter of CollectQualifyingTimes. The string looked like gtstimes.txt or gtsdates.txt or gectimes.txt or gecdates.txt
internal static class DownloadQualifyingTimes
{
//TimeDate Arrays
public static readonly List<string> QDaysList = new List<string>();
public static readonly List<int> QTimesList = new List<int>();
private static StreamReader _reader;
private static string _line;
private static string _file;
/// <summary>
/// Collects the Times
/// </summary>
public static void CollectQualifyingTimes(string fileName)
{
Logger.Debug("About to download the " + fileName + " Qualifying Times and Dates");
FileDownload.DownloadOnlineFile(fileName);
OpenQualifyingFile(fileName);
}
/// <summary>
/// Open the qualifying file and read the values.
/// </summary>
/// <returns></returns>
private static void OpenQualifyingFile(string fileName)
{
try
{
_file = Path + "\\" + fileName;
using (_reader = new StreamReader(_file))
{
while ((_line = _reader.ReadLine()) != null)
{
if (fileName.Contains("Times"))
{
QTimesList.Add(Convert.ToInt16(_line));
Logger.Debug("Times " + _line);
}
else
{
QDaysList.Add(_line);
Logger.Debug("Days " + _line);
}
}
}
}
catch (WebException exception)
{
Logger.Error(exception);
}
}
}
//The method that calls the Downloading class looks like this:
/// <summary>
///
/// </summary>
/// <param name="selectedLeague"></param>
/// <returns></returns>
public static bool QualificationTimeCheck(string selectedLeague)
{
var currentUtcTime = DateTime.UtcNow;
//Day check regardless of league
if (DownloadQualifyingTimes.QDaysList.Contains(currentUtcTime.DayOfWeek.ToString()))
{
Logger.Debug("Qualifying day condition meet");
if (selectedLeague.IsOneOf("GTS", "CAT"))
{
Logger.Debug("GTS or CAT qualifying logic");
if (currentUtcTime.Hour ==
DownloadQualifyingTimes.QTimesList[0] ||
currentUtcTime.Hour ==
DownloadQualifyingTimes.QTimesList[1])
{
Logger.Debug("Qualifying hour condition meet");
if (((currentUtcTime.Minute > DownloadQualifyingTimes.QTimesList[2])
&& (currentUtcTime.Minute < DownloadQualifyingTimes.QTimesList[3])) || SessionObject.LastLapStartedMinute <= DownloadQualifyingTimes.QTimesList[3])
{
Logger.Debug("Qualifying minute condition meet");
return true;
}
I hope this illustrates the nature of my question and the problem.
Can you think of a better way to implement this process? If you need any more information regarding it please don't hesitate to ask.
Edit - Ended up implementing List as per first comment suggestion.
I am having issues with some sample code that I am using from one of Nokia's Imaging SDK samples they provide. Essentially I am trying to save an image to IsolatedStorage. The code that I am reusing has been used successfully elsewhere in the solution, but when I try to use it there are no errors but it does not proceed with the following statements. Essentially in the StorePhoto method, once IBuffer buffer = await App.PhotoModel.RenderFullBufferAsync(); is called no error occurs but no code below that which is actually performs the save to isolated storage operation is ran, so no image is ever saved.
SavePage.xaml.cs
private static string _photoModelPath = #"\Lockscreen\v1\PhotoModel";
private static string _photoModelBufferFilename = #"buffer.data";
public async static void StorePhoto()
{
string _photoModelPath = #"\Lockscreen\v1\LockScreen";
string _photoModelBufferFilename = #"buffer.data";
using (IsolatedStorageFile storage = IsolatedStorageFile.GetUserStoreForApplication())
{
if (!storage.DirectoryExists(_photoModelPath))
{
storage.CreateDirectory(_photoModelPath);
}
if (storage.FileExists(_photoModelPath + #"\" + _photoModelBufferFilename))
{
storage.DeleteFile(_photoModelPath + #"\" + _photoModelBufferFilename);
}
IBuffer buffer = await App.PhotoModel.RenderFullBufferAsync(); //code exiting method with no error
if (buffer != null)
{
IsolatedStorageFileStream originalFile = storage.CreateFile(_photoModelPath + #"\" + _photoModelBufferFilename);
Stream bufferStream = buffer.AsStream();
bufferStream.CopyTo(originalFile);
bufferStream.Flush();
bufferStream.Close();
bufferStream.Dispose();
originalFile.Flush();
originalFile.Close();
originalFile.Dispose();
}
}
}
MainPage.xaml.cs
private async void _saveItem_Click(object sender, EventArgs e)
{
Helpers.SaveHelper.StorePhoto(); //calling the StorePhoto method here
}
PhotoModel.cs (from Nokia Imaging SDK sample)
/// <summary>
/// Renders current image with applied filters to a buffer and returns it.
/// Meant to be used where the filtered image is for example going to be
/// saved to a file.
/// </summary>
/// <returns>Buffer containing the filtered image data</returns>
public async Task<IBuffer> RenderFullBufferAsync()
{
using (BufferImageSource source = new BufferImageSource(_buffer))
using (FilterEffect effect = new FilterEffect(source) { Filters = _components })
using (JpegRenderer renderer = new JpegRenderer(effect))
{
return await renderer.RenderAsync();
}
}
Turns out to solve this I had to put the code that saves the image into the same page that I was originally calling that method, and also it needs to be of type Task so that the async/await will work properly.
I want to notify my web view from button in html file and trigger the javascript:
function notify(str) {
window.external.notify(str);
}
The event captured using wv_ScriptNotify(..., ...):
void wv_ScriptNotify(object sender, NotifyEventArgs e)
{
Color c=Colors.Red;
if (e.CallingUri.Scheme =="ms-appx-web" || e.CallingUri.Scheme == "ms-appdata")
{
if (e.Value.ToLower() == "blue") c = Colors.Blue;
else if (e.Value.ToLower() == "green") c = Colors.Green;
}
appendLog(string.Format("Response from script at '{0}': '{1}'", e.CallingUri, e.Value), c);
}
I set the html file on ms-appx-web and it running well, and I realize that the html file must be store into local folder. So I change the ms-appx-web:///.../index.html to ms-appdata:///local/.../index.html.
Already search in microsoft forum and get this. On that thread there is a solution using resolver, but I'm still confusing, how can it notify from javascript like using window.external.notify? And what kind of event in C# side that will capture the "notify" from javascript other than "ScriptNotify"?
Update
There is a solution from here, example using the resolver and it said to use ms-local-stream:// rather than using ms-appdata://local so I can still use the ScriptNotify event. But unfortunately the example using the ms-appx that means using the InstalledLocation not the LocalFolder.
Trying to googling and search in msdn site for the documentation for ms-local-stream but the only documentation is just the format of ms-local-stream without any example like this ms-local-stream://appname_KEY/folder/file.
Based from that documentation, I made some sample to try it:
public sealed class StreamUriWinRTResolver : IUriToStreamResolver
{
/// <summary>
/// The entry point for resolving a Uri to a stream.
/// </summary>
/// <param name="uri"></param>
/// <returns></returns>
public IAsyncOperation<IInputStream> UriToStreamAsync(Uri uri)
{
if (uri == null)
{
throw new Exception();
}
string path = uri.AbsolutePath;
// Because of the signature of this method, it can't use await, so we
// call into a separate helper method that can use the C# await pattern.
return getContent(path).AsAsyncOperation();
}
/// <summary>
/// Helper that maps the path to package content and resolves the Uri
/// Uses the C# await pattern to coordinate async operations
/// </summary>
private async Task<IInputStream> getContent(string path)
{
// We use a package folder as the source, but the same principle should apply
// when supplying content from other locations
try
{
// My package name is "WebViewResolver"
// The KEY is "MyTag"
string scheme = "ms-local-stream:///WebViewResolver_MyTag/local/MyFolderOnLocal" + path; // Invalid path
// string scheme = "ms-local-stream:///WebViewResolver_MyTag/MyFolderOnLocal" + path; // Invalid path
Uri localUri = new Uri(scheme);
StorageFile f = await StorageFile.GetFileFromApplicationUriAsync(localUri);
IRandomAccessStream stream = await f.OpenAsync(FileAccessMode.Read);
return stream.GetInputStreamAt(0);
}
catch (Exception) { throw new Exception("Invalid path"); }
}
}
And inside my MainPage.xaml.cs:
protected override void OnNavigatedTo(NavigationEventArgs e)
{
// The 'Host' part of the URI for the ms-local-stream protocol needs to be a combination of the package name
// and an application-defined key, which identifies the specific resolver, in this case 'MyTag'.
Uri url = wv.BuildLocalStreamUri("MyTag", "index.html");
StreamUriWinRTResolver myResolver = new StreamUriWinRTResolver();
// Pass the resolver object to the navigate call.
wv.NavigateToLocalStreamUri(url, myResolver);
}
It always get the exception when it reach the StorageFile f = await StorageFile.GetFileFromApplicationUriAsync(localUri); line.
If anybody ever got this problem and already solved it, please advise.
After debugging it, I found something interesting, the BuildLocalStreamUri part is already make the ms-local-stream automatically.
I made some changes on the getContent method inside StreamUriWinRTResolver class:
public sealed class StreamUriWinRTResolver : IUriToStreamResolver
{
/// <summary>
/// The entry point for resolving a Uri to a stream.
/// </summary>
/// <param name="uri"></param>
/// <returns></returns>
public IAsyncOperation<IInputStream> UriToStreamAsync(Uri uri)
{
if (uri == null)
{
throw new Exception();
}
string path = uri.AbsolutePath;
// Because of the signature of this method, it can't use await, so we
// call into a separate helper method that can use the C# await pattern.
return getContent(path).AsAsyncOperation();
}
/// <summary>
/// Helper that maps the path to package content and resolves the Uri
/// Uses the C# await pattern to coordinate async operations
/// </summary>
private async Task<IInputStream> getContent(string path)
{
// We use a package folder as the source, but the same principle should apply
// when supplying content from other locations
try
{
// Don't use "ms-appdata:///" on the scheme string, because inside the path
// will contain "/local/MyFolderOnLocal/index.html"
string scheme = "ms-appdata://" + path;
Uri localUri = new Uri(scheme);
StorageFile f = await StorageFile.GetFileFromApplicationUriAsync(localUri);
IRandomAccessStream stream = await f.OpenAsync(FileAccessMode.Read);
return stream.GetInputStreamAt(0);
}
catch (Exception) { throw new Exception("Invalid path"); }
}
}
Change the file path on the MainPage.xaml.cs:
protected override void OnNavigatedTo(NavigationEventArgs e)
{
// The 'Host' part of the URI for the ms-local-stream protocol needs to be a combination of the package name
// and an application-defined key, which identifies the specific resolver, in this case 'MyTag'.
Uri url = wv.BuildLocalStreamUri("MyTag", "/local/MyFolderOnLocal/index.html");
StreamUriWinRTResolver myResolver = new StreamUriWinRTResolver();
// Pass the resolver object to the navigate call.
wv.NavigateToLocalStreamUri(url, myResolver);
wv.ScriptNotify += wv_ScriptNotify;
}
protected override void wv_ScriptNotify(object sender, NavigationEventArgs e)
{
if (e.CallingUri.Scheme == "ms-local-stream")
{
// Do your work here...
}
}
In libgit2sharp https://github.com/libgit2/libgit2sharp/ how do you check for pending/uncommitted changes?
The following works for me:
///DEPRECATED - see comment from #derptastic
public bool HasUncommittedChanges
{
get
{
using (var repo = new Repository(repositoryRoot))
{
RepositoryStatus status = repo.RetrieveStatus();
return status.IsDirty;
}
}
}
Thanks to #Derptastic for the link to LibGit2Sharp Wiki
The following lines of code will provide the filename and the state of that file.
foreach (var item in repo1.RetrieveStatus())
{
Console.WriteLine(item.FilePath);
Console.WriteLine(item.State);
}
You can use repository.Diff.Compare().
/// <summary>
/// Show changes between the working directory and the index.
/// </summary>
/// <param name = "paths">The list of paths (either files or directories) that should be compared.</param>
/// <returns>A <see cref = "TreeChanges"/> containing the changes between the working directory and the index.</returns>
public virtual TreeChanges Compare(IEnumerable<string> paths = null)
Passing no paths at all should give all changes.
This question already has answers here:
How can I get the assembly last modified date?
(6 answers)
Closed 9 years ago.
How can I retrieve the Created date from the current .NET assembly?
I'd like to add some realy simple functionality where my app stops working one week after the build date of the main assembly. I already wrote the code that kills my app after a given date. I just need to programmatically retrieve the creation date from the assembly.
The following is based on: https://blog.codinghorror.com/determining-build-date-the-hard-way/
public static class ApplicationInformation
{
/// <summary>
/// Gets the executing assembly.
/// </summary>
/// <value>The executing assembly.</value>
public static System.Reflection.Assembly ExecutingAssembly
{
get { return executingAssembly ?? (executingAssembly = System.Reflection.Assembly.GetExecutingAssembly()); }
}
private static System.Reflection.Assembly executingAssembly;
/// <summary>
/// Gets the executing assembly version.
/// </summary>
/// <value>The executing assembly version.</value>
public static System.Version ExecutingAssemblyVersion
{
get { return executingAssemblyVersion ?? (executingAssemblyVersion = ExecutingAssembly.GetName().Version); }
}
private static System.Version executingAssemblyVersion;
/// <summary>
/// Gets the compile date of the currently executing assembly.
/// </summary>
/// <value>The compile date.</value>
public static System.DateTime CompileDate
{
get
{
if (!compileDate.HasValue)
compileDate = RetrieveLinkerTimestamp(ExecutingAssembly.Location);
return compileDate ?? new System.DateTime();
}
}
private static System.DateTime? compileDate;
/// <summary>
/// Retrieves the linker timestamp.
/// </summary>
/// <param name="filePath">The file path.</param>
/// <returns></returns>
/// <remarks>http://www.codinghorror.com/blog/2005/04/determining-build-date-the-hard-way.html</remarks>
private static System.DateTime RetrieveLinkerTimestamp(string filePath)
{
const int peHeaderOffset = 60;
const int linkerTimestampOffset = 8;
var b = new byte[2048];
System.IO.FileStream s = null;
try
{
s = new System.IO.FileStream(filePath, System.IO.FileMode.Open, System.IO.FileAccess.Read);
s.Read(b, 0, 2048);
}
finally
{
if(s != null)
s.Close();
}
var dt = new System.DateTime(1970, 1, 1, 0, 0, 0).AddSeconds(System.BitConverter.ToInt32(b, System.BitConverter.ToInt32(b, peHeaderOffset) + linkerTimestampOffset));
return dt.AddHours(System.TimeZone.CurrentTimeZone.GetUtcOffset(dt).Hours);
}
}
I don't think the assembly itself contains it's creation date. I suspect the closest you can get is the creation date of the assembly file itself:
File.GetCreationTime(Assembly.GetExecutingAssembly().Location)
should do the trick.
EDIT:
I think Jeff Atwood's solution, written up by "grenade" in this thread, is probably the better way to go now.
What's wrong with:
System.IO.File.GetLastWriteTime(Assembly.GetExecutingAssembly().Location);
Maybe this post on coding horror may help
This should work:
var entryAssembly = Assembly.GetEntryAssembly();
var fileInfo = new FileInfo(entryAssembly.Location);
var buildDate = fileInfo.LastWriteTime;
The best way to do this would be with a custom attribute that you set on the PreBuild of your assembly.
And then use the standard reflection to get the attribute you created.
But out of curiosity, why kill the app after the BUILD date?
If you're writing an application for a mobile device using the compact framwork, Assembly.Location is not available.
Here, I found an alternative:
System.IO.Path.GetDirectoryName(System.Reflection.Assembly.GetExecutingAssembly().GetName().CodeBase)