Programatically obtain Email Address of Share point user (SPUser) From Display Name using Linq

This method will take the given  Display Name and looks for associated  email address on User Information List:
               
                    string  strDisplayName = "John Doe";
                    string  strEmailAddress =string.Empty;
                    SPList userInfoList = item.File.Web.SiteUserInfoList;
                    IEnumerable userInfoItem = userInfoList.Items.OfType();
                    var qryEmailAddress = from row in userInfoItem
                                          where Convert.ToString(row["ImnName"]) == strDisplayName
                                          select row;
                    if (qryEmailAddress.Count() > 0)
                    {
                        strEmailAddress = Convert.ToString(qryEmailAddress.First()["EMail"]);
                    }