HttpListenerContext Request QueryString

Question

I've created a sample to do a oauth request toa service.

I'm using a HttpListener to receive the url query string from the redirect_uri, but the redirect_uri that the oauth server sends is like

http://localhost:62941/#access_token=

The # is causing the Request QueryString to be empty.

using var httpListener = new HttpListener();
httpListener.Prefixes.Add("http://localhost:62941/");
httpListener.Start();

//wait for server captures redirect_uri  
HttpListenerContext context = await httpListener.GetContextAsync();

httpListener.Stop();

// the code is null because the QueryString is empty
var code = context.Request.QueryString.Get("access_token");

How can i read the uri from the redirect_uri?

Answer 1

There's a context.Request.Uri.Fragment you can use. You'll just need to split on the = sign.

Answer 2

Hi,@ Frederico Regateiro. Welcome to Microsoft Q&A Forum.

If you are dealing with the OAuth2.0 implicit flow to handle redirects and capture tokens from URL fragments, you could check out the following.

In OAuth 2.0 implicit flow, the authorization server usually sends the access token as part of the URL fragment to the client-side JavaScript. Handling OAuth 2.0 implicit flow often involves using a client-side technology, such as a browser, WebView, or embedded browser control, to handle redirects and capture the token from the URL fragment. The server-side component typically doesn't directly capture the access token in this flow.

Here's a simple example using the WebView2 control in a WPF application:

You could add the Microsoft.Web.WebView2 NuGet package.

MainWindow.xaml:

    <Grid>
        <wv:WebView2 Name="webView" />
    </Grid>

Handle OAuth Flow in Code-Behind (MainWindow.xaml.cs):

 
using System;
using System.Windows;
using Microsoft.Web.WebView2.Core;

public partial class MainWindow : Window
{
    private const string AuthorizationUrl = "YOUR_OAUTH_AUTH_URL";
    private bool isAccessTokenReceived = false;

    public MainWindow()
    {
        InitializeComponent();

        webView.EnsureCoreWebView2Async(null);

        webView.Source = new Uri(AuthorizationUrl);

        webView.CoreWebView2.NavigationCompleted += CoreWebView2_NavigationCompleted;
    }

    private void CoreWebView2_NavigationCompleted(object sender, CoreWebView2NavigationCompletedEventArgs e)
    {
        if (!isAccessTokenReceived && e.Uri.Fragment.Contains("access_token"))
        {
            var uri = new Uri(e.Uri.AbsoluteUri);
            var accessToken = uri.Fragment.Split('=')[1];

            MessageBox.Show($"Access Token: {accessToken}");

            isAccessTokenReceived = true;
            Close();
        }
    }
}

Replace "YOUR_OAUTH_AUTH_URL" with the actual OAuth authorization URL.

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