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c# uwp read csv from web

I am trying to make an app that make use of open data.
The data I try to read out is in a CSV format (and is about 40mb big).
I have 2 problems I can't solve.
First I having difficulties to read the file from the web.
I already read on MSDN how to read files asynchrome but it's all about local files. I want to make a list of objects. Each line (except the first line) contains all props for 1 object
Secondly when I finally managed to read the file, is there a way to save it's data and read it somehow the next time? Because 40mb is pretty big to re-download each time you open the app and it takes a lot of time.
I was wondering if it is possible that when I read the the file on the web again, it will only read and at the new lines.
I am a newbie in UWP (c#) applications, so my apologies for the questions.
Thanks in advance.

There are two APIs you can use to download a file. One is HttpClient, described here on MSDN Documentation and in a UWP sample here. This class is usually recommended for smaller files and smaller data, but can easily handler larger files as well. Its disadvantage is, that when the user closes the app, the file will stop downloading.
The alternative is BackgroundDownloader, again here on MSDN and here in UWP samples. This class is usually recommended for downloading larger files and data, as it automatically perfroms the download in the background so the download will continue even when the app is closed.
To store your files, you can use the ApplicationData.Current.LocalFolder. This is a special folder provided to you by the system for storage of application files. You have read/write access to this folder and you can not only store your files here, but even create subfolder structure using UWP StorageFile and StorageFolder APIs. More about this is on MSDN.

save items in a listbox

In my C# windows application (using visual C# 2012 if you need to know) I need to add things to listboxes and save the items so when the program closes they stay there next time it opens. I would prefer not using the settings to store the information.
Some more things I need for this. Saving them to a text file can't happen either. It needs to be saved in a way that it can not be edited outside of the program.

Sorry but its not possible. Anything that you save can be modified by another program.
You could sign the saved data and then detect that some other has modified the data, but you cannot prevent other programs from read/changing the data.
EDIT
DPAPI can be used to encrypt/decrypt the data. See Really simple encryption with C# and SymmetricAlgorithm

Set up SQL on a web server.
Save the info to your web server.
They can't modify data on a remote server, so I think a database is the way to go.

If you are the only person using that program... I mean... if you are the only one that knows what the program is doing, you could go for saving data in binary format into binary files. I doubt that someone looking at your files will say "Oh damn there is a .bin file in this directory! I have to find a way to discover how to read it and what's it's content!".
As long as you keep your program and its sources protected... I doubt someone will get something out of that content. You transform all your data into a Byte[], you compress it, you encrypt it and you write in a file. Bye bye.

Place to save playlist in music application after exit

I try to create music application and now I am in place where after exit from app I want to save somewhere my playlist to when reopen I have my songs in app.
Where application like winamp save that information ?

You can use Isolated storage. This way is quite easy and transparent. Then you can put some sort of XML into your Isolated storage.
Or you can use some sort of in-proc database engines to store your settings. I would recommend using SQL Server Compact as it is quite natural to use it in .NET.
So you have two options. If you have little amount of information to store (playlist only), I would select Isolated Storage. And when your application grows and settings become more complicated you could switch to SQL Server Compact.

You can use the Isolated Storage API to read and write files specific to your application under the user's profile directory. You can store the playlist in a file in any format you choose; using .NET serialization would be quickest, using XML or JSON will let you arbitrarily customise the output.

Take a look at the Isolated Storage feature, see Introduction to Isolated Storage

string path = Path.Combine(Environment.GetFolderPath(Environment.SpecialFolder.ApplicationData), "MyApplication")

Winamp save the last used playlist in this directory
C:\Users\<username>\AppData\Roaming\Winamp
As for your application, I'd suggest that you use the Isolated Storage API

You could use Application settings which are stored in the user's profile folder.

You can save in a text file or an embedded database like SQLite.

I dont know how winamp does this, but you can do it in many ways. I would create a xml file, or save it in application settings like Darin Dimitrov says it. with the content i need and save it on windows close event. Open it on application start to "restore" application state.

Protecting a Xml file

I'm fairly new to coding, and I just got help figuring out how to create a Xml file; now I want to know, is there a way to protect my Xml file from being edited?
I'm making a simple Command Prompt game, and I'm going to include an Xml file for info storage purposes. Although I don't want the user to be able to change the info contained in the file.. Is there a way to achieve this? It doesn't need to be extensive at this time, due to the program only being a small project.
Anyway, I'm making the program with Visual Studio Pro 2010, and I'm coding it in C#.
Thank you, for any help in advance.

the standard way to verify that parts of your xml has not been modified is to use XML_Signature
this msdn example shows how this is done with dotnet4

I would embed your XML file as a resource of your console application's assembly. The XML file will exist as an embedded resource and not as a seperate file that the user could potentially change. If the user isn't meant to edit a configuration file, don't even let him see it, modify it, or delete it.

look at this topic decrypt and encrypt
i have created my own Encrypter class based from this classes. then you can create it for yourself for next use

You could simply compress it, if you don't need a high level of security. You could use a standard format (ZIP, CAB), or just deflate the stream and store it as a binary file. See the doc and examples about this here: DeflateStream Class

You can't prevent anyone from editing your xml file but you can encrypt your xml file to protect your data.

Best way to store multiple revisions of a text file to a single file

I'm working on a C# application that needs to store all the successive revisions of a given report file to a single project file: each time the (plain text) report file changes, the contents of the new version shall be appended to the project file, along with some metadata. Other requirements:
each version of the report file is 100 kB to 1 MB. Theoritically, the maximum number of revisions is unlimited but it should be less than 1000 in practice.
to keep things simple, I'd like to avoid computing differences between the revisions of the report - just store the whole report to the project file every time it has changed.
the project file should be compressed - it doesn't need to be a text file
it should be easy to retrieve a given version of the report from the application
How can I implement this in an efficient way? Should I create a custom binary file, consider using a database, other ideas?
Many thanks, Guy.

What's wrong with the simple workflow?
Un-gzip file
Append header and new report
Gzip project file
Gzip is a standard format, so it's easily accessible. Subsequent reports probably won't change that much, so you'll have a great compression ratio. To file every report, just open the file and scan the headers. (If scanning doesn't work, also mirror the metadata in an SQLite database, and make sure to include offsets into the project file so you can seek to the right place quickly.)
If your requirements are flexible (e.g. that "shall append" part) and you just want something to keep track of past versions of the file, a revision control system will do all of what you need quite easily.

No need to implement that. I would suggest you to use source control. Personally I use subversion with TortoiseSVN client. There is also a plug-in that integrates Subversion with Visual Studio, VisualSVN. Have a look at them.

If using SVN is not an option, you can just store each revision in an individual file (with filename that represents date for example). You can use separate files for metadata as well. Then all the aforementioned files are zipped into one file (look at http://DotNetZip.codeplex.com/ for example).

I don't think there is much point building this yourself when there are already tens, if not hundreds, of systems that are basically designed to do exactly this - source control systems.
I'd recommend choosing some source control solution that has bindings to C# and store your document in there. Then you can easily check out any revision of the document. You will also be able to diff, branch, etc. if necessary.
To give just one example to get you started you can use Subversion with C# bindings.

You could use alternate data streams to store the old revisions of your file. There is no built-in support in the .NET framework, but there exist some helper classes and articles like here and here.
I have never used this myself, so I can't really tell if this is a good option. But it seems, it would make an elegant solution, since you could store each file version in a separate data stream and only the current version in the "main file". In any case, it will probably only work on NTFS drives.

I think that the already SVN (or another source control system) is a very good idea because source control seems to have exactly the features you require. But if that's not an option you could use a file database like SQL Server Compact Edition or SQLite.