Querying Active Directory from MVC result in: Attempted to access an unloaded appdomain. (Exception from HRESULT: 0x80131014)

I have an issue using c# on .Net 4 in a MVC web application, where when I query Active Directory, I frequently get an error: Attempted to access an unloaded appdomain. (Exception from HRESULT: 0x80131014).

The strange thing is, that it will work flawlessly for a time, and then it will just start happening, and then just disappear again.

I have made a few modifications to the function to get it to work , but they all seem to fail. I am wondering if I am doing something wrong, or if there is a better way to do it.

Here is my current function, that will accept a loginId, and a PrincipalContext. The loginId can either be the user DisplayName i.e "John Smith", or DOMAINNAME\josmi. The default is to use the first 2 letters of their firstname, and then the first 3 letters of their surname. There is a check in there if this is not the case. This part if fine.

public List<ADGroup> GetMemberGroups(string loginId, PrincipalContext principalContext, int tries = 0)
{
    var result = new List<ADGroup>();

    try
    {
        var samAccountName = "";
        if (loginId.Contains(" "))
        {
            var fName = loginId.Split(Char.Parse(" "))[0].ToLower();
            var sName = loginId.Split(Char.Parse(" "))[1].ToLower();

            if (sName.Trim().Length == 2)
                samAccountName = string.Format("{0}{1}", fName.StartsWith(".") ? fName.Substring(0, 4) : fName.Substring(0, 3), sName.Substring(0, 2));
            else
                samAccountName = string.Format("{0}{1}", fName.StartsWith(".") ? fName.Substring(0, 3) : fName.Substring(0, 2), sName.Substring(0, 3));
        }
        else
            samAccountName = loginId.Substring(loginId.IndexOf(@"\") + 1);

        var authPrincipal = UserPrincipal.FindByIdentity(principalContext, IdentityType.SamAccountName, samAccountName);

        if (authPrincipal == null)
            throw new Exception(string.Format("authPrincipal is null for loginId - {0}", loginId));

        var firstLevelGroups = authPrincipal.GetGroups();

        AddGroups(firstLevelGroups, ref result);
    }
    catch
    {
        if (tries > 5)
            throw;

        tries += 1;

        System.Threading.Thread.Sleep(1000);
        GetMemberGroups(loginId, principalContext, tries);
    }

    return result;
}

    private void AddGroups(PrincipalSearchResult<Principal> principal, ref List<ADGroup> returnList)
    {
        foreach (var item in principal)
        {
            if (item.GetGroups().Count() > 0)
                AddGroups(item.GetGroups(), ref returnList);

            returnList.Add(new ADGroup(item.SamAccountName, item.Sid.Value));
        }
    }

This function is called like this:

MembershipGroups = ad.GetMemberGroups(user.SamAccountName, new PrincipalContext(ContextType.Domain));

The the error that I SOMETIMES get is:

System.AppDomainUnloadedException: Attempted to access an unloaded appdomain. (Exception from HRESULT: 0x80131014) at System.StubHelpers.StubHelpers.InternalGetCOMHRExceptionObject(Int32 hr, IntPtr pCPCMD, Object pThis) at System.StubHelpers.StubHelpers.GetCOMHRExceptionObject(Int32 hr, IntPtr pCPCMD, Object pThis) at System.DirectoryServices.AccountManagement.UnsafeNativeMethods.IADsPathname.Retrieve(Int32 lnFormatType) at System.DirectoryServices.AccountManagement.ADStoreCtx.LoadDomainInfo() at System.DirectoryServices.AccountManagement.ADStoreCtx.get_UserSuppliedServerName() at System.DirectoryServices.AccountManagement.ADDNLinkedAttrSet.BuildPathFromDN(String dn) at System.DirectoryServices.AccountManagement.ADDNLinkedAttrSet.MoveNextPrimaryGroupDN() at System.DirectoryServices.AccountManagement.ADDNLinkedAttrSet.MoveNext() at System.DirectoryServices.AccountManagement.FindResultEnumerator1.MoveNext() at System.DirectoryServices.AccountManagement.FindResultEnumerator1.System.Collections.IEnumerator.MoveNext()