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in response to a POST request. Rather, the RFC simply states that the browser should alert the user and present an option to proceed or to cancel without reposting data to the new location. Unless you write complex server code, you can't force POST redirection and preserve posted data.
POST: A form is sent to the server with a post-request and an entry in the database is changed. Redirect: After a post request, the correct webpage with the changed data is delivered to the client using the redirect instruction (HTTP 303). GET: The client requests a confirmation page.
A redirect is an Http response sent to the client. The response contains an Http Header called Location which must contain an absolute url. The client then issues a GET request against this url. So, no, POST is not an option.
For instance, instead of a "form" button that causes a postback and redirect, you could use a LinkButton that will behave like a hyperlink, allowing the browser to request the new page directly.
Doing this requires understanding how HTTP redirects work. When you use Response.Redirect(), you send a response (to the browser that made the request) with HTTP Status Code 302, which tells the browser where to go next. By definition, the browser will make that via a GET request, even if the original request was a POST.
Another option is to use HTTP Status Code 307, which specifies that the browser should make the redirect request in the same way as the original request, but to prompt the user with a security warning. To do that, you would write something like this:
public void PageLoad(object sender, EventArgs e)
{
// Process the post on your side
Response.Status = "307 Temporary Redirect";
Response.AddHeader("Location", "http://example.com/page/to/post.to");
}
Unfortunately, this won't always work. Different browsers implement this differently, since it is not a common status code.
Alas, unlike the Opera and FireFox developers, the IE developers have never read the spec, and even the latest, most secure IE7 will redirect the POST request from domain A to domain B without any warnings or confirmation dialogs! Safari also acts in an interesting manner, while it does not raise a confirmation dialog and performs the redirect, it throws away the POST data, effectively changing 307 redirect into the more common 302.
So, as far as I know, the only way to implement something like this would be to use Javascript. There are two options I can think of off the top of my head:
action attribute point to the third-party server. Then, add a click event to the submit button that first executes an AJAX request to your server with the data, and then allows the form to be submitted to the third-party server.Of the two, I would choose the second, for two reasons. First, it is more reliable than the first because Javascript is not required for it to work; for those who don't have it enabled, you can always make the submit button for the hidden form visible, and instruct them to press it if it takes more than 5 seconds. Second, you can decide what data gets transmitted to the third-party server; if you use just process the form as it goes by, you will be passing along all of the post data, which is not always what you want. Same for the 307 solution, assuming it worked for all of your users.
Hope this helps!
You can use this aproach:
Response.Clear();
StringBuilder sb = new StringBuilder();
sb.Append("<html>");
sb.AppendFormat(@"<body onload='document.forms[""form""].submit()'>");
sb.AppendFormat("<form name='form' action='{0}' method='post'>",postbackUrl);
sb.AppendFormat("<input type='hidden' name='id' value='{0}'>", id);
// Other params go here
sb.Append("</form>");
sb.Append("</body>");
sb.Append("</html>");
Response.Write(sb.ToString());
Response.End();
As result right after client will get all html from server the event onload take place that triggers form submit and post all data to defined postbackUrl.
HttpWebRequest is used for this.
On postback, create a HttpWebRequest to your third party and post the form data, then once that is done, you can Response.Redirect wherever you want.
You get the added advantage that you don't have to name all of your server controls to make the 3rd parties form, you can do this translation when building the POST string.
string url = "3rd Party Url";
StringBuilder postData = new StringBuilder();
postData.Append("first_name=" + HttpUtility.UrlEncode(txtFirstName.Text) + "&");
postData.Append("last_name=" + HttpUtility.UrlEncode(txtLastName.Text));
//ETC for all Form Elements
// Now to Send Data.
StreamWriter writer = null;
HttpWebRequest request = (HttpWebRequest)WebRequest.Create(url);
request.Method = "POST";
request.ContentType = "application/x-www-form-urlencoded";
request.ContentLength = postData.ToString().Length;
try
{
writer = new StreamWriter(request.GetRequestStream());
writer.Write(postData.ToString());
}
finally
{
if (writer != null)
writer.Close();
}
Response.Redirect("NewPage");
However, if you need the user to see the response page from this form, your only option is to utilize Server.Transfer, and that may or may not work.
Something new in ASP.Net 3.5 is this "PostBackUrl" property of ASP buttons. You can set it to the address of the page you want to post directly to, and when that button is clicked, instead of posting back to the same page like normal, it instead posts to the page you've indicated. Handy. Be sure UseSubmitBehavior is also set to TRUE.
This should make life much easier. You can simply use Response.RedirectWithData(...) method in your web application easily.
Imports System.Web
Imports System.Runtime.CompilerServices
Module WebExtensions
<Extension()> _
Public Sub RedirectWithData(ByRef aThis As HttpResponse, ByVal aDestination As String, _
ByVal aData As NameValueCollection)
aThis.Clear()
Dim sb As StringBuilder = New StringBuilder()
sb.Append("<html>")
sb.AppendFormat("<body onload='document.forms[""form""].submit()'>")
sb.AppendFormat("<form name='form' action='{0}' method='post'>", aDestination)
For Each key As String In aData
sb.AppendFormat("<input type='hidden' name='{0}' value='{1}' />", key, aData(key))
Next
sb.Append("</form>")
sb.Append("</body>")
sb.Append("</html>")
aThis.Write(sb.ToString())
aThis.End()
End Sub
End Module
Thought it might interesting to share that heroku does this with it's SSO to Add-on providers
An example of how it works can be seen in the source to the "kensa" tool:
https://github.com/heroku/kensa/blob/d4a56d50dcbebc2d26a4950081acda988937ee10/lib/heroku/kensa/post_proxy.rb
And can be seen in practice if you turn of javascript. Example page source:
<!DOCTYPE HTML>
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<title>Heroku Add-ons SSO</title>
</head>
<body>
<form method="POST" action="https://XXXXXXXX/sso/login">
<input type="hidden" name="email" value="XXXXXXXX" />
<input type="hidden" name="app" value="XXXXXXXXXX" />
<input type="hidden" name="id" value="XXXXXXXX" />
<input type="hidden" name="timestamp" value="1382728968" />
<input type="hidden" name="token" value="XXXXXXX" />
<input type="hidden" name="nav-data" value="XXXXXXXXX" />
</form>
<script type="text/javascript">
document.forms[0].submit();
</script>
</body>
</html>
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