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1100

answers:

5

I work in a office which requires all connections to be made through a specific http proxy. I need to write a simple application to query some values from a webserver - it's easy if there were no proxy. How can I make the C# application proxy-aware? How can I make any sort of connection through a proxy?

+3  A: 

If you are using WebClient, it has a Proxy property you can use.

As other have mentioned, there are several ways to automate proxy setting detection/usage

Web.Config:

<system.net>
   <defaultProxy enabled="true" useDefaultCredentials="true">
     <proxy usesystemdefault="true" bypassonlocal="true" />
   </defaultProxy>
</system.net>

Use of the WebProxy class as described in this article.


You can also cofigure the proxy settings directly (config or code) and your app will then use those.

Web.Config:

<system.net>
  <defaultProxy>
    <proxy
      proxyaddress="http://[proxy address]:[proxy port]"
      bypassonlocal="false"
    />
  </defaultProxy>
</system.net>

Code:

HttpWebRequest request = (HttpWebRequest)WebRequest.Create("url");
WebProxy myproxy = new WebProxy("[proxy address]:[proxy port]", false);
request.Proxy = myproxy;
request.Method = "GET";
HttpWebResponse response = (HttpWebResponse) request.GetResponse();
Oded
+2  A: 

If you want the app to use the system default proxy, add this to your Application.exe.config (where application.exe is the name of your application):

<system.net>
   <defaultProxy enabled="true" useDefaultCredentials="true">
   <proxy usesystemdefault="true" bypassonlocal="true" />
   </defaultProxy>
</system.net>

More details can be found on in the MSDN article on System.Net

Robert Christie
+2  A: 

This is easily achieved either programmatically, in your code, or declaratively in either the web.config or the app.config.

You can programmatically create a proxy like so:

HttpWebRequest request = (HttpWebRequest)WebRequest.Create("[ultimate destination of your request]");
WebProxy myproxy = new WebProxy("[your proxy address]", [your proxy port number]);
myproxy.BypassProxyOnLocal = false;
request.Proxy = myproxy;
request.Method = "GET";
HttpWebResponse response = (HttpWebResponse) request.GetResponse();

You're basically assigning the WebProxy object to the request object's proxy property. This request will then use the proxy you define.

To achieve the same thing declaratively, you can do the following:

<system.net>
  <defaultProxy>
    <proxy
      proxyaddress="http://[your proxy address and port number]"
      bypassonlocal="false"
    />
  </defaultProxy>
</system.net>

within your web.config or app.config. This sets a default proxy that all http requests will use. Depending upon exactly what you need to achieve, you may or may not require some of the additional attributes of the defaultProxy / proxy element, so please refer to the documentation for those.

CraigTP
in programatical example, you did not set the port, WHY?
Skuta
@Skuta - No particular reason. That was merely an oversight as in that example, I'm using the constructor which takes the URL (as a string) and a boolean to determine if local addresses are bypassed. If you need a specific port number, it might be better to use the overloaded constructor that allows the URL (as a string) and the port number (as an Int32), then set the `BypassProxyOnLocal` property to True (if required) immediately afterwards.
CraigTP
@Skuta - I have edited my post to clarify this and to ensure that the programmatic and declarative examples are actually doing the same thing!
CraigTP
A: 

Automatic proxy detection is a process by which a Web proxy server is identified by the system and used to send requests on behalf of the client. This feature is also known as Web Proxy Auto-Discovery (WPAD). When automatic proxy detection is enabled, the system attempts to locate a proxy configuration script that is responsible for returning the set of proxies that can be used for the request.

http://msdn.microsoft.com/en-us/library/fze2ytx2.aspx

Elijah Glover
A: 

This code has worked for me:

WebClient wc = new WebClient();
wc.Proxy.Credentials = CredentialCache.DefaultCredentials;
Foole