SPGroup add doesn't work

Question

I want to add an user to a sharepoint group.

I have the function:

    public static void AddUserInGroup(SPUser user, SPGroup group)
    {
        SPSecurity.RunWithElevatedPrivileges(delegate()
        {
                group.AddUser(user);
        });
    }

group and user are valid.

I don't understand why that code isn't working. What's the reason that SPGroup.AddUser mehod can failed ?

I already have

using(SPSite site = new SPSite(SPContext.Current.Site.ID)
using (SPWeb oWebsite = site.OpenWeb())

before my function

System.Threading.ThreadAbortException: Le thread a été abandonné. à System.Threading.Thread.AbortInternal() à System.Threading.Thread.Abort(Object stateInfo) à System.Web.HttpResponse.AbortCurrentThread() à Microsoft.SharePoint.Utilities.SPUtility.Redirect(String url, SPRedirectFlags flags, HttpContext context, String queryString) à Microsoft.SharePoint.Utilities.SPUtility.RedirectToAccessDeniedPage(HttpContext context) à Microsoft.SharePoint.Utilities.SPUtility.HandleAccessDenied(HttpContext context) à Microsoft.SharePoint.Utilities.SPUtility.HandleAccessDenied(Exception ex) à Microsoft.SharePoint.Library.SPRequest.UpdateMembers(String bstrUrl, UInt32 dwObjectType, String bstrObjId, Guid& pguidScopeId, Int32 lGroupID, Int32 lGroupOwnerId, Object& pvarArrayAdd, Object& pvarArrayAddIds, Object& pvarArrayLoginsRemove, Object& pvarArrayIdsRemove, Boolean bRemoveFromCurrentScopeOnly, Boolean bSendEmail) à Microsoft.SharePoint.SPUserCollection.UpdateMembers(Object objUpdateInfo, Object objAddIds, Object objRemoveLogins, Object objRemoveIds, Boolean fSendEmail) à Microsoft.SharePoint.SPUserCollection.AddCollection(SPUserInfo[] addUsersInfo, IEnumerable`1 addUsers) à Utils.ManageSPGroups.<>c__DisplayClass14.b__13()

Edit 2:

Just for information, this is my new function:

try 
{
    using (SPSite site = new SPSite(SPContext.Current.Site.Url))
    {
        using (SPWeb web = site.OpenWeb(SPContext.Current.Web.ServerRelativeUrl))
        {
            SPSecurity.RunWithElevatedPrivileges(delegate()
            {
                if (!IsUserMemberOfGroup(user.LoginName, groupName))
                {
                    SPGroup oGroup = web.SiteGroups[groupName];
                    oGroup.AddUser(user);
                 }
             });
          }
      }
 }
 catch (Exception ex)
 {
    SPEventLog.WriteError("AddUserIngroup: ", ex);
 }

Answer 1

You're elevating without creating a new site and web object, hence the AddGroup is not elevated at all!

You should create a new SPSite, open the correct SPWeb and then get the group from that elevated object.

You should proably ensure the user first as well, if you do not already

Ex.

using(SPSite site = new SPSite(SPContext.Current.Site.ID)
using (SPWeb oWebsite = site.OpenWeb())
{
    SPGroup oGroup = oWebsite.SiteGroups["Group_Name"];
    var spUser = oWebsite.EnsureUser(user);
    if(spUser != null)
         oGroup.AddUser(spUser);
}

Answer 2

Two more tips on that.

This creates the default groups in your web. The visitors group, member group and owner group. In case that they don't exist you can create them with that code:

                using (SPSite oSPsite = new SPSite(SiteUrl))
                {
                    using (SPWeb oSPWeb = oSPsite.OpenWeb())
                    {
                        //Creates default SharPoint Groups 
                        oSPWeb.EnsureUser(userLoginName);
                        oSPWeb.CreateDefaultAssociatedGroups(userLoginName, userLoginName, oSPWeb.Title);
                        oSPWeb.Update();
                    }
                }

You can also use the webservice usergroup.asmx to add a user to a specific group: http://msdn.microsoft.com/en-us/library/ms772683(v=office.12).aspx

                usrgrpService.AddUserToGroup("Group_Name","User_Display_Name", "DOMAIN\\User_Alias","User_E-mail","Notes");