How Do I Post and then redirect to an external URL from ASP.Net?
Here's how I solved this problem today. I started from this article on C# Corner, but found the example - while technically sound - a little incomplete. Everything he said was right, but I needed to hit a few external sites to piece this together to work exactly as I wanted.
It didn't help that the user was not technically submitting a form at all; they were clicking a link to go to our support center, but to log them in an http post had to be made to the support center's site.
This solution involves using HttpContext.Current.Response.Write() to write the data for the form, then using a bit of Javascript on the <body onload=""> method to submit the form to the proper URL.
When the user clicks on the Support Center link, the following method is called to write the response and redirect the user:
public static void PassthroughAuthentication(){ System.Web.HttpContext.Current.Response.Write("<body onload=document.forms[0].submit();window.location=\"Home.aspx\";>"); System.Web.HttpContext.Current.Response.Write("<form name=\"Form\" target=_blank method=post action=\"https://external-url.com/security.asp\">"); System.Web.HttpContext.Current.Response.Write(string.Format("<input type=hidden name=\"cFName\" value=\"{0}\">", "Username")); System.Web.HttpContext.Current.Response.Write("</form>"); System.Web.HttpContext.Current.Response.Write("</body>");}The key to this method is in that onload bit of Javascript, which , when the body of the page loads, submits the form and then redirects the user back to my own Home page. The reason for that bit of hoodoo is that I'm launching the external site in a new window, but don't want the user to resubmit the hidden form if they refresh the page. Plus that hidden form pushed the page down a few pixels which got on my nerves.
I'd be very interested in any cleaner ideas anyone has on this one.
Eric Sipple
I started with this example from CodeProject
Then instead of adding to the page, I borrowed from saalon (above) and did a Response.Write().
I would do the form post in your code behind using HttpWebRequest class. Here is a good helper class to get your started:
http://geekswithblogs.net/rakker/archive/2006/04/21/76044.aspx
From there, you can just do a Response.Redirect, or perhaps you need to vary your action based on the outcome of the post (if there was an error, display it to the user or whatever). I think you already had the answer in your question to be honest - sounds like you think it is a post OR redirect when in reality you can do them both from your code behind.