SharePoint 判断用户在文件夹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;}