Develop Reference

C# foreach against populated list is returning null

Following some major refactoring (moving to a PCL) I have some code (which was not part of the refactor) that was running fine but is now throwing exceptions.
The code is part of a Xamarin Android project which was using File Linking before the move to a Portable Class Library.
It's a simple thing but I can't see why this would happen
foreach(var station in stationList)
{
// Breakpoint on next line shows station to be null..!
if(station.ClusterId != Guid.Empty)
{
// Code in here
}
}
The problem is that although the stationList contains a number of StationViewModel objects the station instance is always null - how can that be?
I have tried replacing the foreach with a for loop but the result was the same - station was null.
I've also restarted Visual Studio and rebooted.
No Xamarin updates appear to be outstanding.
The code was running fine and the generation of the stationList has not changed nor has the implementation of this class.
EDIT:
The stationList creation process is:
Call made to SQLite 'repo' in PCL which returns IList<station> (which is populated)
_loadedStations = await _stationManager.GetStationsAsync();
Using AutoMapper a new List<StationViewModel> is generated from the above list (which is populated correctly)
fullStationList = AutoMapper.Mapper.Map<IList<Station>, IList<StationViewModel>>(_loadedStations);
In a separate method the view model list above is filtered based on the LatLng coordinates.
var stationList = fullStationList.Where(x => mapBounds.Contains(new LatLng(x.Latitude, x.Longitude))).ToList();
The foreach follows the above line of code..
SOLUTION:
Well I've 'solved' the problem but still don't know what caused it.
In the same method as the foreach there is another, contained within an if. It too has the station identifier;
if (zoomChanged)
{
foreach (var station in fullStationList)
{
station.ClusterId = Guid.Empty;
}
RunOnUiThread(() => _stationMap.Clear());
_clusters.Clear();
}
By changing either of the variable names the code will run fine and the previously erroring loop will run without any problem.
Note that this 2nd loop was not within the 1st one - that's obviously
not going to work, but I can't see why this was causing a problem.

It seems like this has something to do with the way Xamarin works , changing var name solves the issue
foreach(var stationItem in stationList)
{
// Breakpoint on next line shows station to be null..!
if(stationItem.ClusterId != Guid.Empty)
{
// Code in here
}
}

I tried it in this way and it works:
internal class CStation
{
private Guid _clusterId;
public CStation()
{
_clusterId = Guid.NewGuid();
}
public Guid StationName
{
get { return _clusterId; }
}
}
private voit TestList()
{
List<CStation> stationList = new List<CStation>();
CStation test1 = new CStation();
CStation test2 = new CStation();
CStation test3 = new CStation();
stationList.Add(test1);
stationList.Add(test2);
stationList.Add(test3);
foreach (var station in stationList)
{
// Breakpoint on next line shows station to be null..!
if (station == null )
{
throw new ArgumentNullException();
}
}
}
I think you didnt instantiate the Guid.
I did it in the constructor of Station -> _clusterId = Guid.NewGuid();

Get access to the URL's being used in System.Web.Optimization

Background: I'm using the HTML 5 Offline App Cache and dynamically building the manifest file. Basically, the manifest file needs to list each of the static files that your page will request. Works great when the files are actually static, but I'm using Bundling and Minification in System.Web.Optimization, so my files are not static.
When in the DEBUG symbol is loaded (i.e. debugging in VS) then the actual physical files are called from the MVC View. However, when in Release mode, it calls a virtual file that could look something like this: /bundles/scripts/jquery?v=FVs3ACwOLIVInrAl5sdzR2jrCDmVOWFbZMY6g6Q0ulE1
So my question: How can I get that URL in the code to add it to the offline app manifest?
I've tried:
var paths = new List<string>()
{
"~/bundles/styles/common",
"~/bundles/styles/common1024",
"~/bundles/styles/common768",
"~/bundles/styles/common480",
"~/bundles/styles/frontend",
"~/bundles/scripts/jquery",
"~/bundles/scripts/common",
"~/bundles/scripts/frontend"
};
var bundleTable = BundleTable.Bundles;
foreach (var bundle in bundleTable.Where(b => paths.Contains(b.Path)))
{
var bundleContext = new BundleContext(this.HttpContext, bundleTable, bundle.Path);
IEnumerable<BundleFile> files = bundle.GenerateBundleResponse(bundleContext).Files;
foreach (var file in files)
{
var filePath = file.IncludedVirtualPath.TrimStart(new[] { '~' });
sb.AppendFormat(formatFullDomain, filePath);
}
}
As well as replacing GenerateBundleResponse() with EnumerateFiles(), but it just always returns the original file paths.
I'm open to alternative implementation suggestions as well. Thanks.
UPDATE: (7/7/14 13:45)
As well as the answer below I also added this Bundles Registry class to keep a list of the required static files so that it works in debug mode in all browsers. (See comments below)
public class Registry
{
public bool Debug = false;
public Registry()
{
SetDebug();
}
[Conditional("DEBUG")]
private void SetDebug()
{
Debug = true;
}
public IEnumerable<string> CommonScripts
{
get
{
if (Debug)
{
return new string[]{
"/scripts/common/jquery.validate.js",
"/scripts/common/jquery.validate.unobtrusive.js",
"/scripts/common/knockout-3.1.0.debug.js",
"/scripts/common/jquery.timepicker.js",
"/scripts/common/datepicker.js",
"/scripts/common/utils.js",
"/scripts/common/jquery.minicolors.js",
"/scripts/common/chosen.jquery.custom.js"
};
}
else
{
return new string[]{
"/scripts/common/commonbundle.js"
};
}
}
}
}
I'm by no means happy with this solution. Please make suggestions if you can improve on this.

I can suggest an alternative from this blog post create your own token.
In summary the author suggests using web essentials to create the bundled file and then creating a razor helper to generate the token, in this case based on the last changed date and time.
public static class StaticFile
{
public static string Version(string rootRelativePath)
{
if (HttpRuntime.Cache[rootRelativePath] == null)
{
var absolutePath = HostingEnvironment.MapPath(rootRelativePath);
var lastChangedDateTime = File.GetLastWriteTime(absolutePath);
if (rootRelativePath.StartsWith("~"))
{
rootRelativePath = rootRelativePath.Substring(1);
}
var versionedUrl = rootRelativePath + "?v=" + lastChangedDateTime.Ticks;
HttpRuntime.Cache.Insert(rootRelativePath, versionedUrl, new CacheDependency(absolutePath));
}
return HttpRuntime.Cache[rootRelativePath] as string;
}
}
Then you can reference the bundled file like so...
#section scripts {
<script src="#StaticFile.Version("~/Scripts/app/myAppBundle.min.js")"></script>}
Then you have control of the token and can do what you want with it.

SharpCompress unpacking locks files

Im trying to make a process where I unpack a set of rar-files using SharpCompress and then delete them.
I first have a foreach loop which loops over the different set of files to be unpacked like this:
foreach (var package in extractionPackages.Where(package => Extractor.ExtractToFolder(package, destinationFolder)))
{
FileHelper.DeleteExtractionFiles(package);
}
The extraction process is taken straight of the SharpCompress Tests code and goes like this:
public static bool ExtractToFolder(ExtractionPackage extractionPackage, string extractionPath)
{
var fullExtractionPath = Path.Combine(extractionPath, extractionPackage.FolderName);
try
{
using (var reader = RarReader.Open(extractionPackage.ExtractionFiles.Select(p => File.OpenRead(p.FullPath))))
{
while (reader.MoveToNextEntry())
{
reader.WriteEntryToDirectory(fullExtractionPath, ExtractOptions.ExtractFullPath | ExtractOptions.Overwrite);
}
}
return true;
}
catch (Exception)
{
return false;
}
}
As you can see in the first code block I then call to delete the files but there I recieve an error due to that the files are locked by another process:
The process cannot access the file 'file.rar' because it is being used by another process.
If I try to put the deletion after the foreach-loop I am able to delete all but the last set of files if there are more than one. If it is just one the same issue occurs since the last set of files doesn't seems to be "unlocked".
How can I structure the code so that the files is unlocked?

By using an example from Nunrar and modifying it a bit I finally seems to have solved the issue:
public static bool ExtractToFolder(ExtractionPackage extractionPackage, string extractionPath)
{
var fullExtractionPath = Path.Combine(extractionPath, extractionPackage.FolderName);
try
{
using (var reader = RarReader.Open(GetStreams(extractionPackage)))//extractionPackage.ExtractionFiles.Select(p => File.OpenRead(p.FullPath)), Options.None))
{
while (reader.MoveToNextEntry())
{
reader.WriteEntryToDirectory(fullExtractionPath, ExtractOptions.ExtractFullPath | ExtractOptions.Overwrite);
}
}
return true;
}
catch (Exception)
{
return false;
}
}
private static IEnumerable<Stream> GetStreams(ExtractionPackage package)
{
foreach (var item in package.ExtractionFiles)
{
using (Stream input = File.OpenRead(item.FullPath))
{
yield return input;
}
}
}

By default (and probably a flaw) is that I leave the Streams open as I did not create them myself. However, the .NET framework usually breaks this rule with things like StreamReader etc. so it's expected that they'd be closed.
I'm thinking I'm going to change this behavior. In the meantime, you ought to be able to fix this yourself by calling this:
RarReader.Open(extractionPackage.ExtractionFiles.Select(p => File.OpenRead(p.FullPath)), Options.None)

I had a similar trouble. I used SharpCompress for adding files in archive and I need to delete files after archiving. I had tried wrap streams with using() {} - but this solution didn't worked in my case. When I added to my code Application.DoEvents() - it solved the problem.

C# Backing Up And Restoring Clipboard

I have a program that uses clipboard but I want to restore the clipboard to its former state after I am done with it.
This is my code :
IDataObject temp = Clipboard.GetDataObject();
//Some stuff that change Cliboard here
Clipboard.SetText("Hello");
//Some stuff that change Cliboard here
Clipboard.SetDataObject(temp);
But it if I copy a text, and run this code, I get nothing on notepad.
NOTE : I can't use Clipboard.Contains because I want to preserve the Clipboard EXACLY how it was before, even if the user copied a file.

I cannot confirm whether this will work, but I see no reason why you shouldn't be able to back up the data using the longer approach of actually reading the data and restoring it afterwards.
Read here: http://msdn.microsoft.com/en-us/library/system.windows.forms.idataobject.aspx
You would do something like (pseudo-code)
//Backup
var lBackup = new Dictionary<string, object>();
var lDataObject = Clipboard.GetDataObject();
var lFormats = lDataObject.GetFormats(false);
foreach(var lFormat in lFormats)
{
lBackup.Add(lFormat, lDataObject.GetData(lFormat, false));
}
//Set test data
Clipboard.SetText("asd");
//Would be interesting to check the contents of lDataObject here
//Restore data
foreach(var lFormat in lFormats)
{
lDataObject.SetData(lBackup[lFormat]);
}
//This might be unnecessary
Clipboard.SetDataObject(lDataObject);

Is your application exiting after resetting the clipboard?
Assuming it is a Win Form app. (not sure how it works in wpf though)
You could use one of the other overloaded version of Clipboard.SetDataObject
public static void SetDataObject(object data, bool copy)
which preserves the data even after your app exits.
ex: in your case after removing the text content you could call Clipboard.SetDataObject(iDataObject, true);
EDIT:2
I Could source step through Clipboard.cs .NET Frameword 4 / VS 2010.
Download the .NET Framework 4 from here http://referencesource.microsoft.com/netframework.aspx.
Follow the below steps and if it asks for the source (Clipboard.cs) it would be in the Source sub-dir of the installation dir.
EDIT:1
Not sure why the same code doesn't work.
Cannot be a security/permission issue as the code doesn't throw an exception as you say.
There is another approach - source stepping into Framework code - Clipboard.cs
Based on the VS version and .NET framework it may vary ( I couldn't get the source stepping work for .NET 4 as the info is that the symbols with source support haven't yet been released). I'm trying my luck by downloading it manually from here (.NET Version 4)
If you are running VS 2008 and older version of .NET then the below steps should work for you.
More details are here. For .NET Framework 4 - here

This cannot be done. You cannot backup/restore the clipboard without causing unintended consequences.
Please see my post on a similar question. My answer is the one that starts with "It's folly to try to do this".
How do I backup and restore the system clipboard in C#?
Furthermore, I suspect that your motivation for wanting to backup/restore the clipboard is because you want to use it as a crutch to move data, without the user's knowledge or consent. Please read:
http://www.clipboardextender.com/developing-clipboard-aware-programs-for-windows/common-general-clipboard-mistakes
and
http://www.flounder.com/badprogram.htm#clipboard
Lastly, please read and understand this quote:
“Programs should not transfer data into our out of the clipboard without an explicit instruction from the user.” — Charles Petzold, Programming Windows 3.1, Microsoft Press, 1992

I tested the pseudocode from Lukas and found out doesn't work always, this works in all my tests:
// Backup clipboard
lBackup = new Dictionary<string, object>();
lDataObject = Clipboard.GetDataObject();
lFormats = lDataObject.GetFormats(false);
foreach (var lFormat in lFormats)
{
lBackup.Add(lFormat, lDataObject.GetData(lFormat, false));
}
//Set test data
Clipboard.SetText("asd");
//Restore clipboard
lDataObject = new DataObject();
foreach (var lFormat in lFormats)
{
lDataObject.SetData(lFormat, lBackup[lFormat]);
}
//This might be unnecessary
Clipboard.SetDataObject(lDataObject);

I have had success with this.
...to a certain degree.
Where I am currently falling down is trying to copy and restore Bitmaps of varying size.
I can successfully copy and restore a Bitmap of smallish size.
I then tried to do the same for (as the fore-warning Chris Thornton suggested) a gargantuan Excel worksheet with both thousands of cell data, as well as two sets of data on a graph, lying on the same worksheet.
I have found that the data copies and restores without problem. Where it falls down in this instance is allowing the 2-set graph with the worksheet copy.
If any of you have had a problem in copying and restoring Bitmaps, let me suggest what worked for me: when attempting to restore the Clipboard, iterate through the list of formats in reverse order and set each data object that way. (i.e. It seems that a Clipboard must be set in reverse order that it was copied in)
Regarding the case of the gargantuan Excel worksheet and accompanying graph, I also hit another stumbling block: I could not successfully copy the data object whose format was "Meta Data File". That could be the reason why Copy/Restore doesn't work in this case.
I got this far about two weeks ago, and tabled it for more pressing issues.
I wanted to put this out there to let anyone else trying to do the same that it seems like it can be done. (anything can be done in computer science. anything.)

I compiled this code and it seems to work for me. I am persisting via converting to and from json. (Note. It will not do steams so adapt if you need it to)
using Newtonsoft.Json;
using System;
using System.Collections.Generic;
using System.Linq;
using System.Threading;
namespace Clipboard
{
class Program
{
static void Main(string[] args)
{
Execute(() =>
{
var backup = Backup();
System.Windows.Forms.Clipboard.SetText("text"); //just to change clipboard
Restore(backup);
});
}
private static void Execute(Action action)
{
var thread = new Thread(() => action());
thread.SetApartmentState(ApartmentState.STA);
thread.Start();
thread.Join();
}
private static List<ClipboardItem> Backup()
{
var backup = new List<ClipboardItem>();
var data = System.Windows.Forms.Clipboard.GetDataObject();
System.Windows.Forms.Clipboard.SetDataObject(data, copy: true); //This seems to be needed to be able to serialize data later.
data = System.Windows.Forms.Clipboard.GetDataObject();
var formats = data.GetFormats(false).ToList();
formats.ForEach(f =>
{
if (data.GetData(f, false) != null && !(data.GetData(f, false) is Stream))
{
backup.Add(new ClipboardItem()
{
Format = f,
ObjectType = data.GetData(f, false).GetType(),
ObjectJson = JsonConvert.SerializeObject(data.GetData(f, false))
});
}
});
return backup;
}
private static void Restore(List<ClipboardItem> backup)
{
var data = new System.Windows.Forms.DataObject();
backup.ForEach(item =>
{
data.SetData(item.Format, JsonConvert.DeserializeObject(item.ObjectJson, item.ObjectType));
});
System.Windows.Forms.Clipboard.SetDataObject(data, copy: true);
}
}
public class ClipboardItem
{
public string Format { get; set; }
public Type ObjectType { get; set; }
public string ObjectJson { get; set; }
}
}

WP7: collection of images

I have images in folder Images in my windows phone solution. How can i get collection of images in this folder? Build Action of all images is "Content".

It had been bugging me that it wasn't possible to do this so I've done a bit of digging and have come up with a way of getting a list of all image files with the build action of "Resource". - Yes, this isn't quite what was asked for but hopefully this will still be useful.
If you really must use a build action of "Content" I'd use a T4 script to generate the list of files at build time. (This is what I do with one of my projects and it works fine.)
Assuming that the images are in a folder called "images" you can get them with the following:
var listOfImageResources = new StringBuilder();
var asm = Assembly.GetExecutingAssembly();
var mrn = asm.GetManifestResourceNames();
foreach (var resource in mrn)
{
var rm = new ResourceManager(resource.Replace(".resources", ""), asm);
try
{
var NOT_USED = rm.GetStream("app.xaml"); // without getting a stream, next statement doesn't work - bug?
var rs = rm.GetResourceSet(Thread.CurrentThread.CurrentUICulture, false, true);
var enumerator = rs.GetEnumerator();
while (enumerator.MoveNext())
{
if (enumerator.Key.ToString().StartsWith("images/"))
{
listOfImageResources.AppendLine(enumerator.Key.ToString());
}
}
}
catch (MissingManifestResourceException)
{
// Ignore any other embedded resources (they won't contain app.xaml)
}
}
MessageBox.Show(listOfImageResources.ToString());
This just displays a list of the names, but hopefully it'll be easy to change this to do whatever you need to.
Any suggestions for improving this code will be greatly appreciated.