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Getting JSON data from a response stream and reading it as a string?

I am trying to read a response from a server that I receive when I send a POST request. Viewing fiddler, it says it is a JSON response. How do I decode it to a normal string using C# Winforms with preferably no outside APIs. I can provide additional code/fiddler results if you need them.
The fiddler and gibberish images:
The gibberish came from my attempts to read the stream in the code below:
Stream sw = requirejs.GetRequestStream();
sw.Write(logBytes, 0, logBytes.Length);
sw.Close();
response = (HttpWebResponse)requirejs.GetResponse();
Stream stream = response.GetResponseStream();
StreamReader sr = new StreamReader(stream);
MessageBox.Show(sr.ReadToEnd());

As mentioned in the comments, Newtonsoft.Json is really a good library and worth using -- very lightweight.
If you really want to only use Microsoft's .NET libraries, also consider System.Web.Script.Serialization.JavaScriptSerializer.
var serializer = new System.Web.Script.Serialization.JavaScriptSerializer();
var jsonObject = serializer.DeserializeObject(sr.ReadToEnd());

Going to assume (you haven't clarified yet) that you need to actually decode the stream, since A) retrieving a remote stream of text is well documented, and B) you can't do anything much with a non-decoded JSON stream.
Your best course of action is to implement System.Web.Helpers.Json:
using System.Web.Helpers.Json
...
var jsonObj = Json.Decode(jsonStream);

Read only the title and/or META tag of HTML file, without loading complete HTML file

Scenario :
I need to parse millions of HTML files/pages (as fact as I can) & then read only only Title or Meta part of it & Dump it to Database
What I am doing is using System.Net.WebClient Class's DownloadString(url_path) to download & then Saving it to Database by LINQ To SQL
But this DownloadString function gives me complete html source, I just need only Title part & META tag part.
Any ideas, to download only that much content?

I think you can open a stream with this url and use this stream to read the first x bytes, I can't tell the exact number but i think you can set it to reasonable number to get the title and the description.
HttpWebRequest fileToDownload = (HttpWebRequest)HttpWebRequest.Create("YourURL");
using (WebResponse fileDownloadResponse = fileToDownload.GetResponse())
{
using (Stream fileStream = fileDownloadResponse.GetResponseStream())
{
using (StreamReader fileStreamReader = new StreamReader(fileStream))
{
char[] x = new char[Number];
fileStreamReader.Read(x, 0, Number);
string data = "";
foreach (char item in x)
{
data += item.ToString();
}
}
}
}

I suspect that WebClient will try to download the whole page first, in which case you'd probably want a raw client socket. Send the appropriate HTTP request (manually, since you're using raw sockets), start reading the response (which will not be immediately) and kill the connection when you've read enough. However, the rest will have probably already been sent from the server and winging its way to your PC whether you want it or not, so you might not save much - if anything - of the bandwidth.
Depending on what you want it for, many half decent websites have a custom 404 page which is a lot simpler than a known page. Whether that has the information you're after is another matter.

You can use the verb "HEAD" in a HttpWebRequest to return the the response headers (not element. To get the full element with the meta data you'll need to download the page and parse out the meta data you want.
System.Net.WebRequest.Create(uri) { Method = "HEAD" };

Grabbing content from a website in C#

New to C# here, but I've used Java for years. I tried googling this and got a couple of answers that were not quite what I need. I'd like to grab the (X)HTML from a website and then use DOM (actually, CSS selectors are preferable, but whatever works) to grab a particular element. How exactly is this done in C#?

To get the HTML you can use the WebClient object.
To parse the HTML you can use HTMLAgility librrary.

// prepare the web page we will be asking for
HttpWebRequest request = (HttpWebRequest)
WebRequest.Create("http://www.stackoverflow.com");
// execute the request
HttpWebResponse response = (HttpWebResponse)request.GetResponse();
// we will read data via the response stream
Stream resStream = response.GetResponseStream();
string tempString = null;
int count = 0;
do
{
// fill the buffer with data
count = resStream.Read(buf, 0, buf.Length);
// make sure we read some data
if (count != 0)
{
// translate from bytes to ASCII text
tempString = Encoding.ASCII.GetString(buf, 0, count);
// continue building the string
sb.Append(tempString);
}
}
while (count > 0); // any more data to read?
Then use Xquery expressions or Regex to grab the element you need

You could use System.Net.WebClient or System.Net.HttpWebrequest to fetch the page but parsing for the elements is not supported by the classes.
Use HtmlAgilityPack (http://html-agility-pack.net/)
HtmlWeb htmlWeb = new HtmlWeb();
htmlWeb.UseCookies = true;
HtmlDocument htmlDocument = htmlWeb.Load(url);
// after getting the document node
// you can do something like this
foreach (HtmlNode item in htmlDocument.DocumentNode.Descendants("input"))
{
// item mathces your req
// take the item.
}

I hear you want to use the HtmlAgilityPack for working with HTML files. This will give you Linq access, with is A Good Thing (tm). You can download the file with System.Net.WebClient.

You can use Html Agility Pack to load html and find the element you need.

To get you started, you can fairly easily use HttpWebRequest to get the contents of a URL. From there, you will have to do something to parse out the HTML. That is where it starts to get tricky. You can't use a normal XML parser, because many (most?) web site HTML pages aren't 100% valid XML. Web browsers have specially implemented parsers to work around the invalid portions. In Ruby, I would use something like Nokogiri to parse the HTML, so you might want to look for a .NET port of it, or another parser specificly designed to read HTML.
Edit:
Since the topic is likely to come up: WebClient vs. HttpWebRequest/HttpWebResponse
Also, thanks to the others that answered for noting HtmlAgility. I didn't know it existed.

Look into using the html agility pack, which is one of the more common libraries for parsing html.
http://htmlagilitypack.codeplex.com/

Download a file from the internet?

How can I easily download a file from internet in C#?
Thank you very much.

WebClient.DownloadFIle is one simple way.

Have a look at the BCL class System.Net.WebRequest. Here's a brief example:
using System.Net;
...
var request = WebRequest.Create(new Uri("http://..."));
var response = request.GetResponse();
var responseStream = response.GetResponseStream();
// ^^^^^^^^^^^^^^
// read web resource content through this stream object!
...
Take note:
Some of these objects are IDisposable, so in real code you might want to wrap them in using blocks.
The above code example does not do any error checking. You might want to add appropriate code for this, also.

How can I import a raw RSS feed in C#?

Does anyone know an easy way to import a raw, XML RSS feed into C#? Am looking for an easy way to get the XML as a string so I can parse it with a Regex.
Thanks,
-Greg

This should be enough to get you going...
using System.Net
WebClient wc = new WebClient();
Stream st = wc.OpenRead(“http://example.com/feed.rss”);
using (StreamReader sr = new StreamReader(st)) {
string rss = sr.ReadToEnd();
}

If you're on .NET 3.5 you now got built-in support for syndication feeds (RSS and ATOM). Check out this MSDN Magazine Article for a good introduction.
If you really want to parse the string using regex (and parsing XML is not what regex was intended for), the easiest way to get the content is to use the WebClient class.It got a download string which is straight forward to use. Just give it the URL of your feed. Check this link for an example of how to use it.

I would load the feed into an XmlDocument and use XPATH instead of regex, like so:
XmlDocument doc = new XmlDocument();
HttpWebRequest request = WebRequest.Create(feedUrl) as HttpWebRequest;
using (HttpWebResponse response = request.GetResponse() as HttpWebResponse)
{
StreamReader reader = new StreamReader(response.GetResponseStream());
doc.Load(reader);
<parse with XPATH>
}

What are you trying to accomplish?
I found the System.ServiceModel.Syndication classes very helpful when working with feeds.

You might want to have a look at this: http://www.codeproject.com/KB/cs/rssframework.aspx

XmlDocument (located in System.Xml, you will need to add a reference to the dll if it isn't added for you) is what you would use for getting the xml into C#. At that point, just call the InnerXml property which gives the inner Xml in string format then parse with the Regex.

The best way to grab an RSS feed as the requested string would be to use the System.Net.HttpWebRequest class. Once you've set up the HttpWebRequest's parameters (URL, etc.), call the HttpWebRequest.GetResponse() method. From there, you can get a Stream with WebResponse.GetResponseStream(). Then, you can wrap that stream in a System.IO.StreamReader, and call the StreamReader.ReadToEnd(). Voila.

The RSS is just xml and can be streamed to disk easily. Go with Darrel's example - it's all you'll need.