Develop Reference

Xamarin crossplatform Read an xml from online

I have an xml file on server www.testsite.com/sample_file.xml
the structure of xml is like this
<mobileclients>
<clientitem>
<code>SXPFBD</code>
<api>http://SPFD.azurewebsites.net/APIs/</api>
</clientitem>
<clientitem>
<code>STYPFBD</code>
<api>http://SPFD.azurewebsites.net/APIs/</api>
</clientitem>
</mobileclients>
I like to check the code input is present in xml or not using a xamarin cross platform application
I cant keep the file as a resource Since it will keep updating So is it possible to read from an online xml file on the go

Sure, although I would recommend switching to JSON if you can, it is still possible to work with XML.
Here is a code snippet from an app I have developed.
public List<NewsItem> GetNewsItems()
{
var newsXml = XDocument.Load("http://xxxxxxxx.nl/index.php?page=news");
var newsItems = (from newsitem in newsXml.Descendants("newsitem")
select new NewsItem
{
Title = WebUtility.HtmlDecode(newsitem.Element("title").Value),
Message = newsitem.Element("message").Value,
Date = DateTime.ParseExact(newsitem.Element("date").Value, "dd-MM-yyyy HH:mm", CultureInfo.InvariantCulture), // TODO better error handling
User = newsitem.Element("user").Value,
Replies = Convert.ToInt32(newsitem.Element("replies").Value),
Url = newsitem.Element("budgetgamingurl").Value,
Views = Convert.ToInt32(newsitem.Element("views").Value)
}).ToList();
return newsItems;
}
As you can see it loads the document from a URL and handles the XPath queries in-memory.
It is a bit rough, it could use some error handling, but you'll get the basic idea.

UWP Json.Convert storage files

I am making a UWP app in which I am trying to save storage files picked by user to the local settings by serializing them, and I want to deserialize them and use them again when I want to. it saves IReadOnlyList object to the local settings just fine, but at the time of deserializing it gives and exception, that this method cant return storage files because it doesnt have a constructor for this, something like this. I am posting the code of my both methods of saving and loading data. please see it and help me...
public static void SaveState<T>(string key, T value)//save method
{
//key is provided by me so that i can use it to load the data later.
var localSettings = ApplicationData.Current.LocalSettings;
localSettings.Values[key] = JsonConvert.SerializeObject(value);
}
public static T LoadState<T>(string key)//loading data
{
var localSettings = ApplicationData.Current.LocalSettings;
if (localSettings.Values.ContainsKey(key))//exception occurs on the below line
return JsonConvert.DeserializeObject<T>(((string)localSettings.Values[key]));
return default(T);
}
and I use these methods as follows:-
var files = StateService.LoadState<IReadOnlyList<StorageFile>>(Playlist);
//StateService is the class which has these static methods...
Note: when i try to load data with a key which has no data against it in the local settings, it doesnt give any exception and just returns an empty list.but when its supposed to return a filled list of IReadOnlyList then it gives and exception...

I think that JsonConvert.DeserializeObject tries to instantiate IReadOnlyList<StorageFile> but interfaces cannot be instantiated... you should use for example List<StorageFile> as T for setting and reading the list...

I did something like that before and I had the same problem. I did different approach instead of trying to save the StorageFile I saved the json content with the key and always my data is in string ( the json data) and I can use JsonConvert.DeserializeObject<T> without problems.

Saving, loading and manipulating (listview) data C#

I'm working on an UWP application where a user can input data which is placed in a listview. All fine and dandy, but how can I save the user data to a separate file and load it the next time a user boots up the app?
I've tried to find a solution, but I had great difficulty to understand these code snippets and on how to apply these (since I'm fairly new to C# and App development). Would somebody like to explain how I can achieve the saving/loading of the data and explain what the code does?
Thanks in advance! :)

You can create a file like this:
StorageFile ageFile = await local.CreateFileAsync("Age.txt", CreationCollisionOption.FailIfExists);
I can read and write to a file like this:
StorageFolder local = Windows.Storage.ApplicationData.Current.LocalFolder;
var ageFile = await local.OpenStreamForReadAsync(#"Age.txt");
// Read the data.
using (StreamReader streamReader = new StreamReader(ageFile))
{
//Use like a normal streamReader
}
if you are trying to write, use OpenStreamForWriteAsync;

If I understood well, you have some kind of object structure that serves as a model for your ListView. When the application is started, you want to read a file where the data is present. When closing the application (or some other event) write the file with the changes done. Right?
1) When your application is loaded / closed (or upon modifications or some event of your choice), use the Windows.Storage API to read / write the text into the file.
2) If the data you want to write is just a liste of strings, you can save this as is in the file. If it is more complicated, I would recommend serializing it in JSON format. Use JSON.NET to serialize (object -> string) and deserialize (object <- string) the content of your file and object structure.
Product product = new Product();
product.Name = "Apple";
...
string json = JsonConvert.SerializeObject(product);

asp.net Web Form Inputs to CSV File

I have created a web form in asp.NET, unfortunately i do not have the pleasure of being able to use SQL due to some restrictions (internal). I had the idea of exporting the data to a CSV file every time the user clicks submit.
The purpose of this is so that we have a list of computer names, softwares installed, Serial #, ect to keep track.
I have never done anything like this, as i am used to SQL (beginner level), is this even possible, and how would i do it (in code form). I've googled it and all i'm getting is grid view and other forms that i don't want to use, even those seem more complicated than what i want to do. Any help would be appreciated.
I'm using a C# back end to code this.
To clarify, this will be a single CSV file on our network, this web form will only be used internally. So every time someone clicks the submit button it will add a new "row" to the same CSV file. So in the end we have one CSV file with a list of computer names and other information.

Typically you have a model class that represents the data. Here's one:
public class Computer
{
public string SerialNumber {get; set;}
public string Name {get; set;}
public List<string> InstalledSoftware {get; set;}
}
Now that you have a class that can represent the data, it's just a matter of saving or serializing it. You don't have access to a SQL Server database. That's fine. There's other options. You can store it in a structured file format. CSV is not good for this, as you might have multiple pieces of InstalledSoftware per computer, and it's hard to properly handle that with CSV. But other text based formats such as XML and JSON are perfect for this. You can also use "NoSQL" type databases such as MongoDB or RavenDB. You may also be able to use SQLite, which is very lightweight.
Let's start off with some sample data.
List<Computer> computers = new List<Computer>();
computers.Add(new Computer(){
SerialNumber="ABC123",
Name="BOB-LAPTOP",
InstalledSoftware = new List<string>(){
"Notepad", "Visual Studio", "Word"
}
});
computers.Add(new Computer(){
SerialNumber="XYZ456",
Name="JASON-WORKSTATION",
InstalledSoftware = new List<string>(){
"Notepad++", "Visual Studio Code", "Word"
}
});
computers.Add(new Computer(){
SerialNumber="LMN789",
Name="NANCY-SURFACE3",
InstalledSoftware = new List<string>(){
"Outlook", "PowerPoint", "Excel"
}
});
Then it's just a matter of saving the data. Let's try with XML:
var xmlSerializer = new XmlSerializer(typeof(Computer));
using(var stringWriter = new StringWriter())
{
using (var xmlWriter = XmlWriter.Create(stringWriter))
{
xmlSerializer .Serialize(writer, computers);
var xml = stringWriter.ToString();
File.WriteAllText(Server.MapPath("~/App_Data/computers.xml"));
}
}
Or with JSON:
var serializer = new JavaScriptSerializer();
var json = serializer.Serialize(computers);
File.WriteAllText(Server.MapPath("~/App_Data/computers.json"));
Using MongoDB:
var client = new MongoClient(connectionString);
var server = client.GetServer();
var database = server.GetDatabase("ComputerDB");
var computerCollection= database.GetCollection<Computer>("Computers");
foreach(var computer in computers)
{
computerCollection.Insert(computer);
}
Note, I have not tested this code. There's likely bugs. My goal is to give you a starting point, not necessarily 100% working code. I haven't serialized XML in a while and I typically use JSON.NET instead of the built in JavaScriptSerializer.
Also note that if there's any possibility that two users might access the data at the same time, you'll need to take care with the XML and JSON approaches to avoid two people trying to write to the file at once. That's where MongoDB would be better, but you'll have to install the server software somewhere.

Pulling data from a webpage, parsing it for specific pieces, and displaying it

I've been using this site for a long time to find answers to my questions, but I wasn't able to find the answer on this one.
I am working with a small group on a class project. We're to build a small "game trading" website that allows people to register, put in a game they have they want to trade, and accept trades from others or request a trade.
We have the site functioning long ahead of schedule so we're trying to add more to the site. One thing I want to do myself is to link the games that are put in to Metacritic.
Here's what I need to do. I need to (using asp and c# in visual studio 2012) get the correct game page on metacritic, pull its data, parse it for specific parts, and then display the data on our page.
Essentially when you choose a game you want to trade for we want a small div to display with the game's information and rating. I'm wanting to do it this way to learn more and get something out of this project I didn't have to start with.
I was wondering if anyone could tell me where to start. I don't know how to pull data from a page. I'm still trying to figure out if I need to try and write something to automatically search for the game's title and find the page that way or if I can find some way to go straight to the game's page. And once I've gotten the data, I don't know how to pull the specific information I need from it.
One of the things that doesn't make this easy is that I'm learning c++ along with c# and asp so I keep getting my wires crossed. If someone could point me in the right direction it would be a big help. Thanks

This small example uses HtmlAgilityPack, and using XPath selectors to get to the desired elements.
protected void Page_Load(object sender, EventArgs e)
{
string url = "http://www.metacritic.com/game/pc/halo-spartan-assault";
var web = new HtmlAgilityPack.HtmlWeb();
HtmlDocument doc = web.Load(url);
string metascore = doc.DocumentNode.SelectNodes("//*[#id=\"main\"]/div[3]/div/div[2]/div[1]/div[1]/div/div/div[2]/a/span[1]")[0].InnerText;
string userscore = doc.DocumentNode.SelectNodes("//*[#id=\"main\"]/div[3]/div/div[2]/div[1]/div[2]/div[1]/div/div[2]/a/span[1]")[0].InnerText;
string summary = doc.DocumentNode.SelectNodes("//*[#id=\"main\"]/div[3]/div/div[2]/div[2]/div[1]/ul/li/span[2]/span/span[1]")[0].InnerText;
}
An easy way to obtain the XPath for a given element is by using your web browser (I use Chrome) Developer Tools:
Open the Developer Tools (F12 or Ctrl + Shift + C on Windows or Command + Shift + C for Mac).
Select the element in the page that you want the XPath for.
Right click the element in the "Elements" tab.
Click on "Copy as XPath".
You can paste it exactly like that in c# (as shown in my code), but make sure to escape the quotes.
You have to make sure you use some error handling techniques because Web scraping can cause errors if they change the HTML formatting of the page.
Edit
Per #knocte's suggestion, here is the link to the Nuget package for HTMLAgilityPack:
https://www.nuget.org/packages/HtmlAgilityPack/

I looked and Metacritic.com doesn't have an API.
You can use an HttpWebRequest to get the contents of a website as a string.
using System.Net;
using System.IO;
using System.Windows.Forms;
string result = null;
string url = "http://www.stackoverflow.com";
WebResponse response = null;
StreamReader reader = null;
try
{
HttpWebRequest request = (HttpWebRequest)WebRequest.Create(url);
request.Method = "GET";
response = request.GetResponse();
reader = new StreamReader(response.GetResponseStream(), Encoding.UTF8);
result = reader.ReadToEnd();
}
catch (Exception ex)
{
// handle error
MessageBox.Show(ex.Message);
}
finally
{
if (reader != null)
reader.Close();
if (response != null)
response.Close();
}
Then you can parse the string for the data that you want by taking advantage of Metacritic's use of meta tags. Here's the information they have available in meta tags:
og:title
og:type
og:url
og:image
og:site_name
og:description
The format of each tag is: meta name="og:title" content="In a World..."

I recommend Dcsoup. There's a nuget package for it and it uses CSS selectors so it is familiar if you use jquery. I've tried others but it is the best and easiest to use that I've found. There's not much documentation, but it's open source and a port of the java jsoup library that has good documentation. (Documentation for the .NET API here.) I absolutely love it.
var timeoutInMilliseconds = 5000;
var uri = new Uri("http://www.metacritic.com/game/pc/fallout-4");
var doc = Supremes.Dcsoup.Parse(uri, timeoutInMilliseconds);
// <span itemprop="ratingValue">86</span>
var ratingSpan = doc.Select("span[itemprop=ratingValue]");
int ratingValue = int.Parse(ratingSpan.Text);
// selectors match both critic and user scores
var scoreDiv = doc.Select("div.score_summary");
var scoreAnchor = scoreDiv.Select("a.metascore_anchor");
int criticRating = int.Parse(scoreAnchor[0].Text);
float userRating = float.Parse(scoreAnchor[1].Text);

I'd recomend you WebsiteParser - it's based on HtmlAgilityPack (mentioned by Hanlet Escaño) but it makes web scraping easier with attributes and css selectors:
class PersonModel
{
[Selector("#BirdthDate")]
[Converter(typeof(DateTimeConverter))]
public DateTime BirdthDate { get; set; }
}
// ...
PersonModel person = WebContentParser.Parse<PersonModel>(html);
Nuget link