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What is an absolute bare bones httpclient configuration?

I'm coming to .net web api from a JavaScript background, and I'm trying to make a proxy to help with a cross domain JSON request. I'm GETing from a server I don't control the source code for, so I can't configure CORS directly. Likewise, it doesn't speak JSONP.
So two questions as I try to get my head around Web API:
1) Is Httpclient the right tool for this job? (if not, what is?)
2) If httpclient IS the right tool, what is an absolute bare bones httpclient config so I can test this out? Not worried about throwing exceptions or anything else other than just GETing API data and feeding it to a jQuery client.
I guess one other piece of information that would be nice would be building username / password authentication into the http request.
Any help is much appreciated, as are links to any good blogs / tutorials / etc that might help as an introduction to this sort of thing. I've watched several today alone, and I'm still not able to get a basic http request going on the server side without resorting to cutting / pasting other people's code.
Thanks in advance!
** EDIT - To make this question a bit more clear, what I'm trying to test is 1) Can the proxy connect to the third party server, which involves authentication via a username and password 2) Can the proxy then respond to the jQuery client request with the JSON data it received from the third party server.
Thanks to all who have taken the time to respond.

HttpClient seems to be ok in this job.
About the minimal config- it depends on what the third party expects. In most cases would work out-of-the-box, but there always may be some minor tweaks like headers and/or auth code.
I have just found some blog entry where some author shows how to test such a proxy and shows the proxy code too. Please see: http://www.davidbreyer.com/programming/2014/10/11/create-fake-responses-to-rest-service-calls-in-c/
You can find info about sending credentials here: How to use credentials in HttpClient in c#?
HTH
EDIT:
this sample code should work (copied from blog above and modified):
public class Proxy
{
public async Task<ExampleDto> GetExample(int id)
{
var client=new HttpClient();
//set some auth here
//set other headers
var response = client.GetAsync(
string.Format("/api/restserviceexample/{0}", id))
.Result.Content.ReadAsAsync<ExampleDto>();
return await response;
}
}
It's so simple that you can just run it and see if the other server responds. If not, you can play with headers - since all the session info and user auth info are sent using ookies and/or headers, all you have to do is to see how it's made with regular browser and then fake it on the server. Probably best tool for this job will be Fiddler.
However - there is one thing to consider. If the other service has special method for authorization (other than passing credentials with each request) the whole thing becomes tricky, since your proxy should perform authorization using their service, then store their auth cookie on the server or propagate them to the browser and attach them with all next requests.

First, you don't need ASP.NET with C# if you really want minimal.
.NET has great http handling without ASP. Check out classes like HttpListener, HttpListenerContext, HttpListenerRequest, etc... Yes, you'll have to write some boilerplate as your application, but these classes are pretty good.
See among others:
http://www.codeproject.com/script/Articles/ViewDownloads.aspx?aid=599978
Second, if you want user & password, I'd checkout using oauth authentication so you don't have to deal with them directly. Google Plus, Windows Live, Facebook, etc... all have similar OAuth 2.0 APIs for that. See among others:
http://msdn.microsoft.com/en-us/library/dn659750.aspx
https://developers.google.com/+/web/signin/server-side-flow
https://developers.facebook.com/docs/facebook-login/manually-build-a-login-flow/v2.2

How to use Yahoo REST Api in C#

I'm just trying to make an yahoo boot that send to registered user of my application an instant message. I've spent some hours searching the web on how to do it but yahoo developer documentation sucks.First of all I don't know what servers I should use for authorization, log in, and messaging. I have a consumer key and I've tried to follow this steps but nothing works.
Any advice/suggestion is welcome.

The documentation looks to be very good, I think the issue here is that your knowledge of how REST API's work in general is a bit lacking.
Let's talk about diagram #2: Get a request token using: get_request_token.
get_request_token is part of an HTTP endpoint, and in their diagram they want you to pass in a handful of parameters to validate your request.
oauth_consumer_key
oauth_nonce
oauth_signature_method
etc
(If you need more clarification of any step you can find it in the tree view on the left hand side of the page)
The request URL:
https://api.login.yahoo.com/oauth/v2/get_request_token.
Now at this point you can either use the HTTP GET or POST verb. If you decide to use GET you will need to include those above parameters as a query string.
?oath_consumer_key=myConsumerKey&oauth_nonce=oathNonce etc
I will leave it to you to write the associated C# code. You'll want to start off with the HttpWebRequest.Create() method

Encrypted URL results in Bad Request

Before stating the problem I want to say that I've read all the posts that suggest that what I'm doing is a bad idea and I AGREE WITH YOU 100% but, our customer insists that he wants the id on the URL to be encrypted so we don't have much choice.
The application is ASP .Net MVC 2 and we are using the basic default route of
"{controller}/{action}/{id}" in which the id is encrypted.
The code that returns the encrypted id is as follows:
return HttpUtility.UrlEncode(Encryptor.Encrypt(inputText));
The Encrypt method is using the System.Security.Cryptography.RijndaelManaged class and we get something like:
http://localhost:3396/MyController/MyAction/%253fval%253dWrikkm9UeEmHdsaMJyjgzA%253d%253d
Now when I click on the link I always get a blank page saying:
Server Error in '/' Application.
HTTP Error 400 - Bad Request.
I guess this error is being sent by IIS since the request never reaches the controller.
Any help will be very much appreciated.

Perhaps your customer doesn't want people "guessing" incremental or string IDs in the URL, which is how a lot of insecure web applications get hacked (E.g. Sony) right? It's a slightly-uninformed demand, but well intentioned. I understand your pain.
Would your customer know the difference between a hashed and encrypted ID? Maybe your life could be simpler if you just used salted+hashed IDs, which adds just as much obfuscation (not security!) to the URL, minus the need to URLEncode the encrypted value.
Ideally, you could get this "encrypted ID" requirement punted in favor of a combination of SSL, an authentication system with page level rights-enforcement, and solid audit trail logging. This is standard web application security stuff.

How to update note on Facebook using Facebook C# SDK

My website can post a note or a feed into Facebook and receive noteid or feedid.
And now, I need to update a note or feed but i don't know how to do that.
Please help me!!! (^~^)

A Quick Search Found the Notes API Documentation and led me right to Note Editing.

If you want edit note with Graph API, you need send POST request:
https://graph.facebook.com/{NOTE_ID} with both fields: subject and message.
If you send only with one param, another in note set as empty

How to POST Data to another web application (cross domain)

Please consider the following scenario,
There are two web applications App1 & App2. A user would submit his information on App1 though a form. On click of a specific button/link on App1, the same data should be posted to a page on App2 and the user should also be redirected to the same page on App2.
I would like some help in finding out the best way to implement this functionality.
One of the approaches that I have already tried out is by creating a temporary HTML form at runtime, setting the action attribute of the form to the App2 Page and get the form posted by using javascript submit. The data can then be fetched on App2 page by using the response.form object.
This approach works well, but i was still wondering if there is any other way to implement the required functionality.
I would really appriciate if you can give some insights on using RESTful webservices to implement this, or else, using some HttpModule to intercept requests at App1 and modify redirect response to app2 or any other approach that you might find fit for the purpose.
Edit:
Using querystring isnt an option for me.

I've had a need to do similar things with feed agregation and building rss feeds from web page content on different domains.
User Gets app1 page, fills in details and submits then on the server for app1 I have a method that looks like this ...
HTMLDocument FetchURL( string url )
{
WebClient wc = new WebClient();
string remoteContent = wc.DownloadString(url);
// mshtml api is very weird but lets just say you have to do things this way ...
HtmlDocument doc = new HTMLDocument();
IHTMLDocument2 doc2 = (IHTMLDocument2)doc;
doc2.write(new object[] { remoteContent });
return (HTMLDocument)doc2;
}
This function does 2 things of use ...
It gets the page of content at "url"
It parses that content in to a HTMLDocument object
Once you have this function you can then call it passing it the url to the remote page and get back a html doucment.
The functions in the HTMLDocument object will allow you to do javascript like dom queries such as :
docObject.GetElementById("id");
I then have different functions that do different things with this object based on the page / site i'm returning data from.
There is however one fatal flaw here ...
This is likely to work really well with sites that don't change much in structure and are built by code but not so well on less dynamic sites.
With stackoverflow for example its easy to pull out a question and the accepted answer for that question so I could use this code to pull and publish content from here on my own web site.
However ...
This is not going to help you for user / login related details as this sort of information is not shared to generally everyone.
It's bit like me going and trying this to link facebook profiles to my own website, I would have to go through some form of api that asked the user to authenticate their details before making the request.
simply pulling a web page based on a url only will give the other site no authentication information unless that site accepts the user login details in the quesrystring and you already have them.
You may however be able to chain requests by ripping apart my sample method, requesting the login page parsing the results, filling in the form, then posting back using the same web client instance to login then requesting the url.
The idea being that you would have a form that asks the user to put in their login details for the remote site on your site then you go and find their profile page based on that.
This would be best farmed out to a class rather than just a simple method like i have here.
In my case though i was only after something simple (the bbc top 40 uk charts) which i pulled information from not only the bbc but places like amazon, google, and youtube, then i built a page :)
It's neat but serves no functional purpose other than pulling all your other fave sources of info on to 1 page.

If you are already committed to using javascript, then why not an ajax post, and change the window.location based on the response?

You can use HttpServerUtility.Transfer this will preserve your form contents and transfer the user to the new page.
http://msdn.microsoft.com/en-us/library/system.web.httpserverutility.transfer.aspx

I have built something like what you are describing, and I found that using a <form> tag to POST to app2 is the most reliable way... basically, the way you found that worked well.

If App2 is residing on a different domain, it's usually best to create your own interface for the submission, and have that interface handle the posting from App1 to App2.
(Browser) -> Submits form to App1 ->
(App1) -> validate input
-> stores local info
-> creates an HttpRequest/POST object
-> posts to App2
(App2) -> handles the post
<- returns the response
-> confirms the results of App2
<- returns the results to the browser.
In essense, you want to control and proxy requests from your Applications domain to any outside interfaces as much as possible.

Note: I'm answering my own question
just to have a correct answers marked
against it. All the suggestions
provided by various members here are
correct in their own way, but they
were not apt for my requirements.
Hence, I cant accept any of them as
correct.
The way I have Implemented is by creating a custom control which would have a configurable property containing the URL to post data and another one accepting a dictionary object as the data input to be posted.
This control would internally create a HTML form with action attribute set to the URL specified by the user and have the data feilds created out of the dictionary object. This form would then be posted on the button click event on the page hosting this control.