I'm trying to pass data via post method from my client to a server.
I'm using WebApi to do so.
This i the code i used:
client:
var client = new RestClient();
client.EndPoint = #"http://localhost:57363/hello";
client.Method = HttpVerb.POST;
client.PostData = "{value: Hello}";
var json = client.MakeRequest();
Console.WriteLine(json);
Console.Read();
server:
// POST api/<controller>
public string Post([FromBody]string value)
{
return value + ", world.";
}
The server responds as expected when using postman. However, the client passes a null value instead of the real value.
What am i doing wrong?
First of all a correct json would look like "{value: 'Hello'}".
I use json-online to easily validate such inline json.
On the other hand, I think that you should send just the value in this case, not the entire json (because you are trying to resolve a simple type,a string), so the client should send a request like:
client.PostData = "'Hello'";
how can i directly call my own server side function using XMLHttpRequest.
suppose i have one static webmethod in my aspx file then how can i call it by XMLHttpRequest. what header info i need to pass to asp.net engine and as a result asp.net engine can invoke my method and return the response back in the out going stream.
this way i need to call my server side method
<script type="text/javascript">
var request;
// A
// Here is the new function that is called when the user submits the form.
// This example uses POST.
function submitCallback() {
var inputValue = document.getElementById("SearchInput").value;
var sendStr = "name=" + inputValue;
request = new XMLHttpRequest();
// B
// Specify the POST method and send it.
request.open("POST", "Default.aspx/Getdata");
request.onreadystatechange = readyCallback;
request.setRequestHeader("Content-Type", "application/x-www-form-urlencoded");
request.setRequestHeader("IsLookup", "true");
request.send(sendStr);
}
</script>
please guide me....thanks
I believe you are probably referring to ASP.NET Page Methods when you say One static webmethod in my aspx file. ASP.NET page methods (or web services for consumption in JS) uses JSON serialization for i/p and o/p. So you need to set JSON as the content type for the request and actually send the JSON string in the body i.e.
...
var sendStr = "{name:" + inputValue + "}";
...
request.setRequestHeader("Content-Type", "application/json");
...
request.send(sendStr);
Further, I will suggest you to use jquery or ASP.NET generated proxies (by ScriptManager) instead of directly coding against XmlHttpRequest. See this article for how to use jquery for calling Page methods.
I think, the easiest way will be usage of jQuery for ajax requests: http://api.jquery.com/category/ajax/
I need to upload and save an image onto the server. I am using an XMLHttpRequest POST to send the image to the server and calling a class named imageSave.aspx.
I am finding difficulty in "catching" the image from server side (imageSave.aspx) and saving it onto the server.
Does anyone please have some tips as to how this is done or maybe link to a good article or something?
Code used to perform the http POST....
xhr = new XMLHttpRequest();
// Update progress bar etc
xhr.upload.addEventListener("progress", function(evt) {
if (evt.lengthComputable) {
progressBar.style.width = (evt.loaded / evt.total) * 100 + "%";
}
else {
// No data to calculate on
}
}, false);
// File uploaded
xhr.addEventListener("load", function() {
progressBarContainer.className += " uploaded";
progressBar.innerHTML = "Uploaded!";
}, false);
xhr.open("post", "imageSave.aspx", true);
// Set appropriate headers
xhr.setRequestHeader("Content-Type", "multipart/form-data");
xhr.setRequestHeader("X-File-Name", file.fileName);
xhr.setRequestHeader("X-File-Size", file.fileSize);
xhr.setRequestHeader("X-File-Type", file.type);
// Send the file
xhr.send(file);
Much appreciated,
JP
Read this other answer:
What data formats can AJAX transfer?
It'll get you an idea of why you can't upload an image using XMLHttpRequest.
UPDATE: Check this control of AJAX Control Toolkit - it'd be what you want! - :
http://www.asp.net/ajax/ajaxcontroltoolkit/samples/asyncfileupload/asyncfileupload.aspx
I'm fairly new to ASP.NET. And I was wondering how I could go about getting xml from a site (Kuler's API in this case), and then post the result using AJAX?
So what I want here, is to be able to do a query to Kuler's API. The URL would be something like "http://kuler-api.adobe.com/rss/search.cfm?query="+queryVariable
Then send the resulting xml back to JS in some way.
Any pointers would be appreciated (:
What you'll need to do is have a handler that will perform the request for the XML and send it back to the browser using AJAX. It will act as an intermediary between server and client, and you won't have to worry about cross-domain policies.
This is what I do on one of my sites. I have a handler (let's call it proxy.ashx) that I call from a jQuery AJAX request. The proxy.ashx simply performs a WebClient.DownloadString action on the remote URL and sends the remote response (the XML) back to the client-side.
I think that Tim said enough, but what I would like to add is how you could do the server side request:
XmlDocument doc = new XmlDocument();
HttpWebRequest r = (HttpWebRequest)HttpWebRequest.Create("http://kuler-api.adobe.com/rss/search.cfm?query="+queryVariable);
r.Method = "POST";
using (Stream writeStream = r.GetRequestStream())
{
UTF8Encoding encoding = new UTF8Encoding();
byte[] bytes = encoding.GetBytes(bodyRequest);
writeStream.Write(bytes, 0, bytes.Length);
}
try
{
using (HttpWebResponse response = (HttpWebResponse)r.GetResponse())
{
using (Stream responseStream = response.GetResponseStream())
{
using (StreamReader readStream = new StreamReader(responseStream, Encoding.UTF8))
{
doc.Load(readStream);
}
}
}
}
catch (WebException ex)
{
//Handle exception
}
I'd do the whole thing in Javascript using Jquery's ajax library, if possible. It's very simple to use and you don't have to worry about getting the XML from server to client that way.
Write a .net webservice (.asmx) that encapsulate the cross domain call, then call that service with AJAX.
We have the requirement to take a form submission and save some data, then redirect the user to a page offsite, but in redirecting, we need to "submit" a form with POST, not GET.
I was hoping there was an easy way to accomplish this, but I'm starting to think there isn't. I think I must now create a simple other page, with just the form that I want, redirect to it, populate the form variables, then do a body.onload call to a script that merely calls document.forms[0].submit();
Can anyone tell me if there is an alternative? We might need to tweak this later in the project, and it might get sort of complicated, so if there was an easy we could do this all non-other page dependent that would be fantastic.
Anyway, thanks for any and all responses.
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:
Create the form and have its 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.
Create the form to post to your server. When the form is submitted, show the user a page that has a form in it with all of the data you want to pass on, all in hidden inputs. Just show a message like "Redirecting...". Then, add a javascript event to the page that submits the form 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.
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>
PostbackUrl can be set on your asp button to post to a different page.
if you need to do it in codebehind, try Server.Transfer.
#Matt,
You can still use the HttpWebRequest, then direct the response you receive to the actual outputstream response, this would serve the response back to the user. The only issue is that any relative urls would be broken.
Still, that may work.
I suggest building an HttpWebRequest to programmatically execute your POST and then redirect after reading the Response if applicable.
Here's what I'd do :
Put the data in a standard form (with no runat="server" attribute) and set the action of the form to post to the target off-site page.
Before submitting I would submit the data to my server using an XmlHttpRequest and analyze the response. If the response means you should go ahead with the offsite POSTing then I (the JavaScript) would proceed with the post otherwise I would redirect to a page on my site
In PHP, you can send POST data with cURL. Is there something comparable for .NET?
Yes, HttpWebRequest, see my post below.
The GET (and HEAD) method should never be used to do anything that has side-effects. A side-effect might be updating the state of a web application, or it might be charging your credit card. If an action has side-effects another method (POST) should be used instead.
So, a user (or their browser) shouldn't be held accountable for something done by a GET. If some harmful or expensive side-effect occurred as the result of a GET, that would be the fault of the web application, not the user. According to the spec, a user agent must not automatically follow a redirect unless it is a response to a GET or HEAD request.
Of course, a lot of GET requests do have some side-effects, even if it's just appending to a log file. The important thing is that the application, not the user, should be held responsible for those effects.
The relevant sections of the HTTP spec are 9.1.1 and 9.1.2, and 10.3.
Typically, all you'll ever need is to carry some state between these two requests. There's actually a really funky way to do this which doesn't rely on JavaScript (think <noscript/>).
Set-Cookie: name=value; Max-Age=120; Path=/redirect.html
With that cookie there, you can in the following request to /redirect.html retrieve the name=value info, you can store any kind of information in this name/value pair string, up to say 4K of data (typical cookie limit). Of course you should avoid this and store status codes and flag bits instead.
Upon receiving this request you in return respond with a delete request for that status code.
Set-Cookie: name=value; Max-Age=0; Path=/redirect.html
My HTTP is a bit rusty I've been going trough RFC2109 and RFC2965 to figure how reliable this really is, preferably I would want the cookie to round trip exactly once but that doesn't seem to be possible, also, third-party cookies might be a problem for you if you are relocating to another domain. This is still possible but not as painless as when you're doing stuff within your own domain.
The problem here is concurrency, if a power user is using multiple tabs and manages to interleave a couple of requests belonging to the same session (this is very unlikely, but not impossible) this may lead to inconsistencies in your application.
It's the <noscript/> way of doing HTTP round trips without meaningless URLs and JavaScript
I provide this code as a prof of concept: If this code is run in a context that you are not familiar with I think you can work out what part is what.
The idea is that you call Relocate with some state when you redirect, and the URL which you relocated calls GetState to get the data (if any).
const string StateCookieName = "state";
static int StateCookieID;
protected void Relocate(string url, object state)
{
var key = "__" + StateCookieName + Interlocked
.Add(ref StateCookieID, 1).ToInvariantString();
var absoluteExpiration = DateTime.Now
.Add(new TimeSpan(120 * TimeSpan.TicksPerSecond));
Context.Cache.Insert(key, state, null, absoluteExpiration,
Cache.NoSlidingExpiration);
var path = Context.Response.ApplyAppPathModifier(url);
Context.Response.Cookies
.Add(new HttpCookie(StateCookieName, key)
{
Path = path,
Expires = absoluteExpiration
});
Context.Response.Redirect(path, false);
}
protected TData GetState<TData>()
where TData : class
{
var cookie = Context.Request.Cookies[StateCookieName];
if (cookie != null)
{
var key = cookie.Value;
if (key.IsNonEmpty())
{
var obj = Context.Cache.Remove(key);
Context.Response.Cookies
.Add(new HttpCookie(StateCookieName)
{
Path = cookie.Path,
Expires = new DateTime(1970, 1, 1)
});
return obj as TData;
}
}
return null;
}
Copy-pasteable code based on Pavlo Neyman's method
RedirectPost(string url, T bodyPayload) and GetPostData() are for those who just want to dump some strongly typed data in the source page and fetch it back in the target one.
The data must be serializeable by NewtonSoft Json.NET and you need to reference the library of course.
Just copy-paste into your page(s) or better yet base class for your pages and use it anywhere in you application.
My heart goes out to all of you who still have to use Web Forms in 2019 for whatever reason.
protected void RedirectPost(string url, IEnumerable<KeyValuePair<string,string>> fields)
{
Response.Clear();
const string template =
#"<html>
<body onload='document.forms[""form""].submit()'>
<form name='form' action='{0}' method='post'>
{1}
</form>
</body>
</html>";
var fieldsSection = string.Join(
Environment.NewLine,
fields.Select(x => $"<input type='hidden' name='{HttpUtility.UrlEncode(x.Key)}' value='{HttpUtility.UrlEncode(x.Value)}'>")
);
var html = string.Format(template, HttpUtility.UrlEncode(url), fieldsSection);
Response.Write(html);
Response.End();
}
private const string JsonDataFieldName = "_jsonData";
protected void RedirectPost<T>(string url, T bodyPayload)
{
var json = JsonConvert.SerializeObject(bodyPayload, Formatting.Indented);
//explicit type declaration to prevent recursion
IEnumerable<KeyValuePair<string, string>> postFields = new List<KeyValuePair<string, string>>()
{new KeyValuePair<string, string>(JsonDataFieldName, json)};
RedirectPost(url, postFields);
}
protected T GetPostData<T>() where T: class
{
var urlEncodedFieldData = Request.Params[JsonDataFieldName];
if (string.IsNullOrEmpty(urlEncodedFieldData))
{
return null;// default(T);
}
var fieldData = HttpUtility.UrlDecode(urlEncodedFieldData);
var result = JsonConvert.DeserializeObject<T>(fieldData);
return result;
}