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How to know if a website/domain is available before loading a webview with that URL

hello I am trying to launch an intent with a webview from a user entered URL, I have been looking everywhere online and I can't find a concrete answer as to how to make sure the website will actually connect before allowing the user to proceed to the next activity. I have found many tools to make sure the URL follows the correct format but none that actually let me make sure it can actually connect.

You can use WebClient and check if any exception is thrown:
using (var client = new HeadOnlyClient())
{
try
{
client.DownloadString("http://google.com");
}
catch (Exception ex)
{
// URL is not accessible.
}
}
You can catch more specific exceptions to make it more elegant.
You can also use custom modification to WebClient to check HEAD only and decrease the amount of data downloaded:
class HeadOnlyClient : WebClient
{
protected override WebRequest GetWebRequest(Uri address)
{
WebRequest req = base.GetWebRequest(address);
req.Method = "HEAD";
return req;
}
}

I would suggest you to use HttpHead for simple request with AndroidHttpClient, but it is deprecated now. You can try to implement HEAD Request by sockets.

You can try to ping the address first.
See this SO question: How to Ping External IP from Java Android

Another option:
Connectivity Plugin for Xamarin and Windows
Task<bool> IsReachable(string host, int msTimeout = 5000);
But, any pre-check that succeeds isn't guaranteed as the very next request might fail so you should still handle that.

Here's what I ended up doing to Check if a Host name is reachable. I was connecting to a site with a self signed certificate so that's why I have the delegate in the ServiceCertificateValidationCallback.
private async Task<bool> CheckHostConnectionAsync (string serverName)
{
string Message = string.Empty;
HttpWebRequest request = (HttpWebRequest)HttpWebRequest.Create(serverName);
ServicePointManager.ServerCertificateValidationCallback += delegate
{
return true;
};
// Set the credentials to the current user account
request.Credentials = System.Net.CredentialCache.DefaultCredentials;
request.Method = "GET";
request.Timeout = 1000 * 40;
try
{
using (HttpWebResponse response = (HttpWebResponse) await request.GetResponseAsync ())
{
// Do nothing; we're only testing to see if we can get the response
}
}
catch (WebException ex)
{
Message += ((Message.Length > 0) ? "\n" : "") + ex.Message;
return false;
}
if (Message.Length == 0)
{
goToMainActivity (serverName);
}
return true;
}

Requests POI from a location using Xamarin (Android)

Im trying to create an android app with xamarin.I want the user to be able to input an address/location and receive POI (Points of Interest) near it (within a certain radius).
I know google places api can do this, does xamarin have built in capability for something like this? Can I somehow interface with the Google Places api?
Or is there something I don't know about? Thanks for the help!

Use HTTPWebRequest class to create a request to Google API, code snippet:
private void button1_Click(object sender, EventArgs e)
{
HttpWebRequest webRequest = WebRequest.Create(#"https://maps.googleapis.com/maps/api/place/search/json?location=-33.8670522,151.1957362&radius=7500&types=library&sensor=false&key=AIzaSyD3jfeMZK1SWfRFDgMfxn_zrGRSjE7S8Vg") as HttpWebRequest;
webRequest.Timeout = 20000;
webRequest.Method = "GET";
webRequest.BeginGetResponse(new AsyncCallback(RequestCompleted), webRequest);
}
private void RequestCompleted(IAsyncResult result)
{
var request = (HttpWebRequest)result.AsyncState;
var response = (HttpWebResponse)request.EndGetResponse(result);
using (var stream = response.GetResponseStream())
{
var r = new StreamReader(stream);
var resp = r.ReadToEnd();
}
}
copy over from here... pretty straightforward and simple...

Http Post for Windows Phone 8

I am new to C# so I was wondering if someone can help me out on this. I am trying to send HttpPost from Windows Phone 8 to the server. I found two examples that I would like to combine.
The first one is an example of sending Http Post (http://msdn.microsoft.com/en-us/library/system.net.httpwebrequest.begingetrequeststream.aspx). The problem with this one is that it is not support by Windows Phone 8.
The second example is using the BeginGetResponse (http://msdn.microsoft.com/en-us/library/windowsphone/develop/system.net.httpwebrequest(v=vs.105).aspx). This supports windows phone 8.
I need to convert the second example into a BeginGetRequestStream() like the first example. I will try to figure out this myself, but I am posting online if someone already knows how to do this. I am sure this will be helpful for other WP8 developers.
Update
I am now trying to get response from the server. I have started a new question. Please follow this link (Http Post Get Response Error for Windows Phone 8)

I am also currently working on a Windows Phone 8 project and here is how I am posting to a server. Windows Phone 8 sort of has limited access to the full .NET capabilities and most guide I read say you need to be using the async versions of all the functions.
// server to POST to
string url = "myserver.com/path/to/my/post";
// HTTP web request
var httpWebRequest = (HttpWebRequest)WebRequest.Create(url);
httpWebRequest.ContentType = "text/plain; charset=utf-8";
httpWebRequest.Method = "POST";
// Write the request Asynchronously
using (var stream = await Task.Factory.FromAsync<Stream>(httpWebRequest.BeginGetRequestStream,
httpWebRequest.EndGetRequestStream, null))
{
//create some json string
string json = "{ \"my\" : \"json\" }";
// convert json to byte array
byte[] jsonAsBytes = Encoding.UTF8.GetBytes(json);
// Write the bytes to the stream
await stream.WriteAsync(jsonAsBytes, 0, jsonAsBytes.Length);
}

I propose a more generic asynchronous approach supporting success and error callbacks here:
//Our generic success callback accepts a stream - to read whatever got sent back from server
public delegate void RESTSuccessCallback(Stream stream);
//the generic fail callback accepts a string - possible dynamic /hardcoded error/exception message from client side
public delegate void RESTErrorCallback(String reason);
public void post(Uri uri, Dictionary<String, String> post_params, Dictionary<String, String> extra_headers, RESTSuccessCallback success_callback, RESTErrorCallback error_callback)
{
HttpWebRequest request = WebRequest.CreateHttp(uri);
//we could move the content-type into a function argument too.
request.ContentType = "application/x-www-form-urlencoded";
request.Method = "POST";
//this might be helpful for APIs that require setting custom headers...
if (extra_headers != null)
foreach (String header in extra_headers.Keys)
try
{
request.Headers[header] = extra_headers[header];
}
catch (Exception) { }
//we first obtain an input stream to which to write the body of the HTTP POST
request.BeginGetRequestStream((IAsyncResult result) =>
{
HttpWebRequest preq = result.AsyncState as HttpWebRequest;
if (preq != null)
{
Stream postStream = preq.EndGetRequestStream(result);
//allow for dynamic spec of post body
StringBuilder postParamBuilder = new StringBuilder();
if (post_params != null)
foreach (String key in post_params.Keys)
postParamBuilder.Append(String.Format("{0}={1}&", key, post_params[key]));
Byte[] byteArray = Encoding.UTF8.GetBytes(postParamBuilder.ToString());
//guess one could just accept a byte[] [via function argument] for arbitrary data types - images, audio,...
postStream.Write(byteArray, 0, byteArray.Length);
postStream.Close();
//we can then finalize the request...
preq.BeginGetResponse((IAsyncResult final_result) =>
{
HttpWebRequest req = final_result.AsyncState as HttpWebRequest;
if (req != null)
{
try
{
//we call the success callback as long as we get a response stream
WebResponse response = req.EndGetResponse(final_result);
success_callback(response.GetResponseStream());
}
catch (WebException e)
{
//otherwise call the error/failure callback
error_callback(e.Message);
return;
}
}
}, preq);
}
}, request);
}

webresponse not updating the XML

i m facing a problem with WebResponse Property it is not properly updating in my Windows phone 7 application.
ReceiveData() // I m calling this Function recursively, With Timer.
{
strurl = "http://www.***Mylivedatawebsite.com/api/rates.php";
webRequest = (HttpWebRequest)WebRequest.Create(strurl);
webRequest.BeginGetResponse(new AsyncCallback(FinishWebRequest), null);
}
FinishWebRequest(IAsyncResult result)
{
WebResponse resp = webRequest.EndGetResponse(result);
StreamReader objReader = new StreamReader(resp.GetResponseStream());
XDocument Doc = XDocument.Load(objReader);
}
The Doc contains the same value after parsing. Please help me out.

In a windows phone 7, usually the webservice response is cached. You can use incremental approach in the url's attribute. Here's the sample below.
static int increment= 0;
strurl = "http://www.***Mylivedatawebsite.com/api/rates.php"+ "id =" + (increment++).ToString();
In this way when the webservice wil see a different attribute id then it will make a re-request to the server.

Get web page contents from Firefox in a C# program

I need to write a simple C# app that should receive entire contents of a web page currently opened in Firefox. Is there any way to do it directly from C#? If not, is it possible to develop some kind of plug-in that would transfer page contents? As I am a total newbie in Firefox plug-ins programming, I'd really appreciate any info on getting me started quickly. Maybe there are some sources I can use as a reference? Doc links? Recommendations?
UPD: I actually need to communicate with a Firefox instance, not get contents of a web page from a given URL

It would help if you elaborate What you are trying to achieve. May be plugins already out there such as firebug can help.
Anways, if you really want to develop both plugin and C# application:
Check out this tutorial on firefox extension:
http://robertnyman.com/2009/01/24/how-to-develop-a-firefox-extension/
Otherwise, You can use WebRequest or HttpWebRequest class in .NET request to get the HTML source of any URL.

I think you'd almost certainly need to write a Firefox plugin for that. However there are certainly ways to request a webpage, and receive its HTML response within C#. It depends on what your requirements are?
If you're requirements are simply receive the source from any website, leave a comment and I'll point you towards the code.

Uri uri = new Uri(url);
System.Net.HttpWebRequest req = (System.Net.HttpWebRequest)System.Net.WebRequest.Create(uri.AbsoluteUri);
req.AllowAutoRedirect = true;
req.MaximumAutomaticRedirections = 3;
//req.UserAgent = _UserAgent; //"Mozilla/6.0 (MSIE 6.0; Windows NT 5.1; Searcharoo.NET)";
req.KeepAlive = true;
req.Timeout = _RequestTimeout * 1000; //prefRequestTimeout
// SIMONJONES http://codeproject.com/aspnet/spideroo.asp?msg=1421158#xx1421158xx
req.CookieContainer = new System.Net.CookieContainer();
req.CookieContainer.Add(_CookieContainer.GetCookies(uri));
System.Net.HttpWebResponse webresponse = null;
try
{
webresponse = (System.Net.HttpWebResponse)req.GetResponse();
}
catch (Exception ex)
{
webresponse = null;
Console.Write("request for url failed: {0} {1}", url, ex.Message);
}
if (webresponse != null)
{
webresponse.Cookies = req.CookieContainer.GetCookies(req.RequestUri);
// handle cookies (need to do this incase we have any session cookies)
foreach (System.Net.Cookie retCookie in webresponse.Cookies)
{
bool cookieFound = false;
foreach (System.Net.Cookie oldCookie in _CookieContainer.GetCookies(uri))
{
if (retCookie.Name.Equals(oldCookie.Name))
{
oldCookie.Value = retCookie.Value;
cookieFound = true;
}
}
if (!cookieFound)
{
_CookieContainer.Add(retCookie);
}
}
string enc = "utf-8"; // default
if (webresponse.ContentEncoding != String.Empty)
{
// Use the HttpHeader Content-Type in preference to the one set in META
doc.Encoding = webresponse.ContentEncoding;
}
else if (doc.Encoding == String.Empty)
{
doc.Encoding = enc; // default
}
//http://www.c-sharpcorner.com/Code/2003/Dec/ReadingWebPageSources.asp
System.IO.StreamReader stream = new System.IO.StreamReader
(webresponse.GetResponseStream(), System.Text.Encoding.GetEncoding(doc.Encoding));
webresponse.Close();

This does what you want.
using System.Net;
var cli = new WebClient();
string data = cli.DownloadString("http://www.heise.de");
Console.WriteLine(data);

Native messaging enables an extension to exchange messages with a native application installed on the user's computer.