C# WebBrowser -> WebView2 solution

Hi Trish, sure.

        // Helper function to extract the authorization code from the URL
        private static string ExtractAuthorizationCode(string uri)
        {
            var uriObj = new Uri(uri);
            var queryParams = HttpUtility.ParseQueryString(uriObj.Query);
            return queryParams["code"];
        }

Here's the whole class:

    public static class OAuthLogin
    {
        private const string CsOAuthServer = "https://secure.myob.com/oauth2/account/authorize/";
        private const string CsOAuthScope = "CompanyFile";
        private static string _currentUri = string.Empty;

        public static async Task<string> GetAuthorizationCode(IApiConfiguration config)
        {
            // Format the URL for the OAuth server login
            string url = string.Format("{0}?client_id={1}&redirect_uri={2}&scope={3}&response_type=code",
                                       CsOAuthServer, config.ClientId, HttpUtility.UrlEncode(config.RedirectUrl), CsOAuthScope);

            // Create a new form with WebView2
            var frm = new Form();
            var webView2 = new WebView2
            {
                Dock = DockStyle.Fill
            };
            frm.Controls.Add(webView2);

            // Set up a TaskCompletionSource to signal when the form can close
            var tcs = new TaskCompletionSource<string>();

            // Subscribe to NavigationCompleted to capture the OAuth redirect
            webView2.CoreWebView2InitializationCompleted += (sender, args) =>
            {
                if (args.IsSuccess)
                {
                    // Navigate to the OAuth login URL
                    webView2.CoreWebView2.Navigate(url);
                }
            };

            // Capture the URL in NavigationStarting
            webView2.NavigationStarting += (sender, args) =>
            {
                // Store the URI when navigation starts
                _currentUri = args.Uri;
            };

            // Use NavigationCompleted to check if the URI contains the authorization code
            webView2.NavigationCompleted += (sender, args) =>
            {
                if (_currentUri.Contains("code="))
                {
                    // Extract the authorization code from the URL
                    string code = ExtractAuthorizationCode(_currentUri);

                    // Signal the TaskCompletionSource that the form can close with the code
                    tcs.SetResult(code);

                    // Close the form
                    frm.Invoke((MethodInvoker)(() => frm.Close()));
                }
            };

            // Initialize WebView2 control asynchronously
            await webView2.EnsureCoreWebView2Async(null);

            frm.Size = new Size(800, 600);
            frm.Show();

            // Wait until the TaskCompletionSource is signaled (form is closed)
            string authCode = await tcs.Task;

            return authCode;

        }

        // Helper function to extract the authorization code from the URL
        private static string ExtractAuthorizationCode(string uri)
        {
            var uriObj = new Uri(uri);
            var queryParams = HttpUtility.ParseQueryString(uriObj.Query);
            return queryParams["code"];
        }

    }