SharePoint 判断用户在文件夹上是否有权限的方法

判断一个用户在SPItem上是否有权限的方法：

public static bool UserInItemExists(SPWeb web, SPListItem item, string strUserLoginName)
{
    bool boolResult = false;
    try
    {
        if (item != null)
        {
            SPRoleAssignmentCollection roles = item.RoleAssignments;

            foreach (SPRoleAssignment role in roles)
            {
                sbResult.Append(role.Member.Name.ToUpper().Trim());

                SPUser loginuser = null;
                try
                {
                    loginuser = new SPSite(SPContext.Current.Site.Url).RootWeb.Users[strUserLoginName];
                }
                catch
                {
                    loginuser = null;
                }

                SPUser memberuser = null;
                try
                {
                    memberuser = ((Microsoft.SharePoint.SPUser)(role.Member));
                }
                catch
                {
                    memberuser = null;
                }

                if (loginuser != null && memberuser != null)
                {
                    if (loginuser.Sid == memberuser.Sid)
                    {
                        boolResult = true;
                        break;
                    }
                }
            }
        }
    }
    catch { }

    return boolResult;
}