/// <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);
}
