(C# UWP/WinRT) REST Follow Redirects

Demonstrates how to follow a 302/303 redirect response.

Chilkat Universal Windows Platform (UWP) / WinRT Downloads Chilkat for the Universal Windows Platform (UWP)

// This example requires the Chilkat API to have been previously unlocked.
// See Global Unlock Sample for sample code.

Chilkat.Rest rest = new Chilkat.Rest();

bool bTls = true;
int port = 443;
bool bAutoReconnect = true;
bool success = await rest.ConnectAsync("chilkatsoft.com",port,bTls,bAutoReconnect);
if (success != true) {
    Debug.WriteLine(rest.LastErrorText);
    return;
}

// Send a POST to a URL that will respond with a 302 redirect..
rest.AddQueryParam("firstName","John");
rest.AddQueryParam("lastName","Doe");
string responseText = await rest.FullRequestFormUrlEncodedAsync("POST","/echoPost302.asp");
if (rest.LastMethodSuccess != true) {
    Debug.WriteLine(rest.LastErrorText);
    return;
}

int statusCode = rest.ResponseStatusCode;

// Examine the response status code
if (statusCode < 300) {
    Debug.WriteLine("Not a redirect.");
    Debug.WriteLine(responseText);
    return;
}

if (statusCode > 399) {
    Debug.WriteLine("Error response: Status code = " + Convert.ToString(statusCode));
    Debug.WriteLine(responseText);
    return;
}

Debug.WriteLine("Redirect status code = " + Convert.ToString(statusCode));

// The response header will contain a Location field with the redirect URL, such as this:
// Location: http://www.chilkatsoft.com/echoPostFinal.asp

// The response status code determines how the client should behave.
// Here are some common possibilities:

// 301: Moved Permanently
// This and all future requests should be directed to the given URI.  (Keep the original HTTP method for the redirect.  In this case, the 
// original request was a POST, so we POST to the redirect URL.)

// 302: Found (aka Object Moved aka Moved Temporarily)
// This is the most popular redirect code, but also an example of industrial practice contradicting the standard. HTTP/1.0 specification (RFC 1945 ) required the client
// to perform a temporary redirect (the original describing phrase was Moved Temporarily), but popular browsers implemented it as a 303 See Other. Therefore, HTTP/1.1
// added status codes 303 and 307 to disambiguate between the two behaviors. However, the majority of Web applications and frameworks still use the 302 status code
// as if it were the 303.

// 303: See Other
// The response to the request can be found under another URI using a GET method. When received in response to a PUT, it should be assumed that the server has
// received the data and the redirect should be issued with a separate GET message.

// 307: Temporary Redirect
// In this occasion, the request should be repeated with another URI, but future requests can still use the original URI. In contrast to 303, the request method
// should not be changed when reissuing the original request. For instance, a POST request must be repeated using another POST request.

Debug.WriteLine(rest.ResponseHeader);

Chilkat.Url redirectUrl = rest.RedirectUrl();
if (rest.LastMethodSuccess == false) {
    Debug.WriteLine("No Location header found for redirect.");
    return;
}

// Prep for the redirect..
rest.ClearAllParts();

// Disconnect and re-connect.  
// (This can be skipped if both the host and SSL/TLS conditions are the same.)
await rest.DisconnectAsync(100);
success = await rest.ConnectAsync(redirectUrl.Host,redirectUrl.Port,redirectUrl.Ssl,bAutoReconnect);
if (success != true) {
    Debug.WriteLine(rest.LastErrorText);
    return;
}

if ((statusCode == 301) || (statusCode == 307)) {
    // Redirect using a POST, sending the same params to the new destination
    rest.AddQueryParam("firstName","John");
    rest.AddQueryParam("lastName","Doe");
    responseText = await rest.FullRequestFormUrlEncodedAsync("POST",redirectUrl.Path);
    if (rest.LastMethodSuccess != true) {
        Debug.WriteLine(rest.LastErrorText);
        return;
    }

}

if ((statusCode == 302) || (statusCode == 303)) {
    // Redirect using a GET, sending the query params found in the redirect URL.
    responseText = await rest.FullRequestFormUrlEncodedAsync("GET",redirectUrl.PathWithQueryParams);
    if (rest.LastMethodSuccess != true) {
        Debug.WriteLine(rest.LastErrorText);
        return;
    }

}

// Show the final status code and the response text.
Debug.WriteLine("Final status code = " + Convert.ToString(rest.ResponseStatusCode));

Debug.WriteLine("Final response text (HTML, XML, JSON, or whatever..)");
Debug.WriteLine(responseText);