C# : Access denied reading SharePoint groups from context user

Question

I've made a SharePoint Provider Hosted App. Into the App Web Project, displayed through a Web Part in my SharePoint Page, I have a web page named Default.aspx.

On this page I have a button, on which I attached an event listener on click.

Here is the relevant C# code-behind of this page :

public void btnSave_Click(object sender, EventArgs e)
{
       //string userName = this.Context.User.Identity.Name;
       bool isAdmin = false;
       SPUser user = SPContext.Current.Web.CurrentUser;
       try
       {
            if (user.Groups["Administrators_Sharepoint"] != null)
            {
                isAdmin = true;
            }
            else
            {
                isAdmin = false;
            }
        }
        catch
        {
            notificationArea.InnerHtml = "identification error";
        }
        //SPGroup adminGroup = site.Groups["Administrators_Sharepoint"];
        //bool isAdmin = site.IsCurrentUserMemberOfGroup(7);

        if (isAdmin)
        {
            notificationArea.InnerHtml = "OK !";
        }
}

Issue : When I try to read a value of the Groups list of user, the page returned is the one saying "Let us know why you need to access this site" :

If I remove the user.Groups[xxxxx],or user.Groups.xxx calls from my page, it will correctly execute the code and not display this message.

Note : the user context I get is the good one, and the account is farm and site administrator for test purposes. So I don't understand why I should have an access denial on this.

EDIT : In the SharePoint logs, when checking the query sent I got a System.UnauthorizedAccessException error at Microsoft.SharePoint.SPWeb.InitWeb() .... at ActivityBoxWeb.Pages.Default.btnSave_Click(Object sender, EventArgs e)

I've added to my App read and write rights for site collection, for test purposes. Not solved yet.

EDIT 2 : With the system account of Sharepoint, it works. He is in the same group of my administrator user. They have the exact same rights.

EDIT 3 : It's totally insane. Others members of the security group doesn't have this "Let us know why you need to access to this site" request page. I am the only one, with the same rights, to land on this access denied page.

Thanks for guiding me, can't figure out how to trace the origin of this issue

Answer 1

I have also faced similar kind of issue in one of my event receiver,

I changed "Who can view the membership of the group" to everyone. This resolved my issue.

Answer 2

Hi app installed in SharePoint can't access all the details from the hosted web. in project you have to specify the permission in app-manifest.xml that what content you want to access from host web. This will get the permission while installing the app and only tenant administrator and access the complete details about users information and some other thing. so may be user group also need permission so check bellow screen shot here you can see the how to get the access to the host web contents.

Check the permissions tab in the AppManifest.xml windows