Proper Way to check page permissions for Sharepoint Online

Question

I am checking permissions if a user has permissions (at least read) to a calendar page on sharepoint online. This code does not seem to always work meaning give Access Denied even though I can see the calendar by going to the URL. Code always breaks at last Executequery so I know it sees the list. Also, not sure if it checks if Everyone as access to and therefor the user does. CalendarUrl: https://microsoft.sharepoint.com/stuff/stuffer/Lists/theCal/calendar.aspx siteUrl = "https://microsoft.sharepoint.com/stuff/stuffer"

try
{
    ClientContext clientContext = new ClientContext(siteUrl);
    string userLogin = "i:0#.f|membership|" + owner.ToLower();
    List oList = clientContext.Web.Lists.GetByTitle(listName);
    clientContext.Load(oList);
    clientContext.ExecuteQuery();

    User usr = clientContext.Web.EnsureUser(userLogin);
    clientContext.Load(usr);
    clientContext.ExecuteQuery();

    ClientResult<BasePermissions> result = item.GetUserEffectivePermissions(usr.LoginName);
    clientContext.ExecuteQuery();

    if(result.Value.Has(PermissionKind.ViewListItems))
    {
        return CallStatus.Ok;
    }
}
catch (Exception ex)
{
    //User has no permission
}

What should I do to get an 'OK' for a user to have permission on the calendar page either directly or through "Everyone" setting on the calendar page? Thanks again.

Answer 1

The following example demonstrates how to verify whether the user has access to page using HttpResponse.Status property:

public static bool CanAccessPage(string pageUrl,ICredentials credentials)
{
    var request = WebRequest.Create(pageUrl);
    request.Credentials = credentials;
    request.Headers.Add("X-FORMS_BASED_AUTH_ACCEPTED", "f");
    try
    {
        using (request.GetResponse())
        {
           return true;
        }
    }
    catch (WebException e)
    {
       using (var response = e.Response)
       {
          var httpResponse = (HttpWebResponse)response;
          if (httpResponse.StatusCode == HttpStatusCode.Forbidden)
               return false;
          throw;
       }
    }
}

Example

var pageUrl = "https://contoso.sharepoint.com/Pages/LatestNews.aspx";
var credentials = new SharePointOnlineCredentials(userName, securePassword);
if (CanAccessPage(pageUrl,credentials))
{
    //...            
}