Using Remote event receiver on list item adding create SPGroup in Autohosted App

Question

I am trying to create remote event receiver on the list which is created in my app. I want to create SharePoint group when I add item in the list.
I have questions like:

1. Is it possible to create group in AppWeb? Though the event receiver of my list will create ClientContext of appweb URL.
2. If above is not possible then how can I get the HostWeb URL from the ClientContext which is created for the appweb?
3. Is there any other way to create ClientContext for the hostweb URL from the Remote event receiver created for the list in my app web?

Thank you in advance...!

Answer 1

Groups are always created at the root level. An appweb is a subsite, so you cannot create groups inside it. However, you can create groups in Hostweb root site by creating a client context object of HostWeb in case you use APP Event Receiver.

using (ClientContext clientContext = TokenHelper.CreateAppEventClientContext(properties, false))

You need to pass the second parameter as false in TokenHelper.reateAppEventClientContext. You can get host web url in Remote event receiver using query string. hostUrl = new Uri(Request.QueryString["SPHostUrl"]);

Finally you need to give the app Full Control permissions on the Host web. Follwing code can be used to create groups:

private void CreateGroup(GroupCollection collGroup, string groupName, Web oWebsite, ClientContext clientContext)
{
    Group grp = collGroup.Where(g => g.Title == groupName).FirstOrDefault();
    if (grp == null)
    {
        GroupCreationInformation groupCreationInfo = new GroupCreationInformation();
        groupCreationInfo.Title = groupName;
        groupCreationInfo.Description = "Description of " + groupName;
        Group oGroup = oWebsite.SiteGroups.Add(groupCreationInfo);
        RoleDefinitionBindingCollection collRoleDefinitionBinding = new RoleDefinitionBindingCollection(clientContext);
        RoleDefinition oRoleDefinition = oWebsite.RoleDefinitions.GetByType(RoleType.Contributor);
        collRoleDefinitionBinding.Add(oRoleDefinition);
        oWebsite.RoleAssignments.Add(oGroup, collRoleDefinitionBinding);
        clientContext.Load(oGroup, group => group.Title);
        clientContext.Load(oRoleDefinition, role => role.Name);
        clientContext.ExecuteQuery();
    }
}

For more information please see my blog. Here I create groups in APP Event Receiver http://sharepointnadeem.blogspot.com/2014/02/sharepoint-2013-app-event-receivers.html

Answer 2

As shown here: Remote Event Receiver on host web

You can use:

            // Workaround for getting client context. If not used, users are not able to create sites.
            string webUrl = properties.ItemEventProperties.WebUrl;

            Uri webUri = new Uri(webUrl);

            string realm = TokenHelper.GetRealmFromTargetUrl(webUri);

            string accessToken = TokenHelper.GetAppOnlyAccessToken(TokenHelper.SharePointPrincipal, webUri.Authority, realm).AccessToken;
            using (var clientContext = TokenHelper.GetClientContextWithAccessToken(webUrl, accessToken))
            {

            }