protected override void SaveSharePointContext(SharePointContext spContext, HttpContextBase httpContext)
 {
     httpContext.Session[SPContextKey] = spContext as SharePointHighTrustContext;
 }
 /// <summary>
 /// Validates if the given SharePointContext can be used with the specified HTTP context.
 /// </summary>
 /// <param name="spContext">The SharePointContext.</param>
 /// <param name="httpContext">The HTTP context.</param>
 /// <returns>True if the given SharePointContext can be used with the specified HTTP context.</returns>
 protected abstract bool ValidateSharePointContext(SharePointContext spContext, HttpContextBase httpContext);
 /// <summary>
 /// Saves the specified SharePointContext instance associated with the specified HTTP context.
 /// <c>null</c> is accepted for clearing the SharePointContext instance associated with the HTTP context.
 /// </summary>
 /// <param name="spContext">The SharePointContext instance to be saved, or <c>null</c>.</param>
 /// <param name="httpContext">The HTTP context.</param>
 protected abstract void SaveSharePointContext(SharePointContext spContext, HttpContextBase httpContext);
        /// <summary>
        /// Checks if it is necessary to redirect to SharePoint for user to authenticate.
        /// </summary>
        /// <param name="httpContext">The HTTP context.</param>
        /// <param name="redirectUrl">The redirect url to SharePoint if the status is ShouldRedirect. <c>Null</c> if the status is Ok or CanNotRedirect.</param>
        /// <returns>Redirection status.</returns>
        public static RedirectionStatus CheckRedirectionStatus(HttpContextBase httpContext, out Uri redirectUrl)
        {
            if (httpContext == null)
            {
                throw new ArgumentNullException("httpContext");
            }

            redirectUrl = null;

            if (SharePointContextProvider.Current.GetSharePointContext(httpContext) != null)
            {
                return(RedirectionStatus.Ok);
            }

            const string SPHasRedirectedToSharePointKey = "SPHasRedirectedToSharePoint";

            if (!string.IsNullOrEmpty(httpContext.Request.QueryString[SPHasRedirectedToSharePointKey]))
            {
                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);
        }