ASPC.Marvel.CrimeAPI.SharePointContextProvider.CheckRedirectionStatus C# (CSharp) Метод

        public static RedirectionStatus CheckRedirectionStatus(HttpContextBase httpContext, out Uri redirectUrl)
        {
            if (httpContext == null)
            {
                throw new ArgumentNullException("httpContext");
            }

            redirectUrl = null;
            bool contextTokenExpired = false;

            try
            {
                if (SharePointContextProvider.Current.GetSharePointContext(httpContext) != null)
                {
                    return RedirectionStatus.Ok;
                }
            }
            catch (SecurityTokenExpiredException)
            {
                contextTokenExpired = true;
            }

            const string SPHasRedirectedToSharePointKey = "SPHasRedirectedToSharePoint";

            if (!string.IsNullOrEmpty(httpContext.Request.QueryString[SPHasRedirectedToSharePointKey]) && !contextTokenExpired)
            {
                return RedirectionStatus.CanNotRedirect;
            }

            Uri spHostUrl = SharePointContext.GetSPHostUrl(httpContext.Request);

            if (spHostUrl == null)
            {
                return RedirectionStatus.CanNotRedirect;
            }

            if (StringComparer.OrdinalIgnoreCase.Equals(httpContext.Request.HttpMethod, "POST"))
            {
                return RedirectionStatus.CanNotRedirect;
            }

            Uri requestUrl = httpContext.Request.Url;

            var queryNameValueCollection = HttpUtility.ParseQueryString(requestUrl.Query);

            // Removes the values that are included in {StandardTokens}, as {StandardTokens} will be inserted at the beginning of the query string.
            queryNameValueCollection.Remove(SharePointContext.SPHostUrlKey);
            queryNameValueCollection.Remove(SharePointContext.SPAppWebUrlKey);
            queryNameValueCollection.Remove(SharePointContext.SPLanguageKey);
            queryNameValueCollection.Remove(SharePointContext.SPClientTagKey);
            queryNameValueCollection.Remove(SharePointContext.SPProductNumberKey);

            // Adds SPHasRedirectedToSharePoint=1.
            queryNameValueCollection.Add(SPHasRedirectedToSharePointKey, "1");

            UriBuilder returnUrlBuilder = new UriBuilder(requestUrl);
            returnUrlBuilder.Query = queryNameValueCollection.ToString();

            // Inserts StandardTokens.
            const string StandardTokens = "{StandardTokens}";
            string returnUrlString = returnUrlBuilder.Uri.AbsoluteUri;
            returnUrlString = returnUrlString.Insert(returnUrlString.IndexOf("?") + 1, StandardTokens + "&");

            // Constructs redirect url.
            string redirectUrlString = TokenHelper.GetAppContextTokenRequestUrl(spHostUrl.AbsoluteUri, Uri.EscapeDataString(returnUrlString));

            redirectUrl = new Uri(redirectUrlString, UriKind.Absolute);

            return RedirectionStatus.ShouldRedirect;
        }