Searching for a file/doc in a document library in Sharepoint

//Call my document library’s listservice webservice 
Sharepoint_WebService.Lists listService = new Sharepoint_WebService.Lists();
                            listService.Credentials = new System.Net.NetworkCredential("username", "password");
                            //get the entire list items from the specified document library
                            XmlNode ndList = listService.GetListItems(accountName, null, null, null, null, null, null);
                            XmlNamespaceManager nsMgr = new XmlNamespaceManager(ndList.OwnerDocument.NameTable);
                            nsMgr.AddNamespace("rs"”, "urn:schemas-microsoft-com:rowset");
                            nsMgr.AddNamespace("z", "#RowsetSchema");
                            //if the document library is empty
                            if (ndList != null)
                            {
                                XmlNode dataNode = ndList.SelectSingleNode("rs:data", nsMgr);
                                int itemCount = Convert.ToInt32(dataNode.Attributes.GetNamedItem("ItemCount").Value);
                                if (itemCount == 0)
                                {
                                    MessageBox.Show("No file to search");                               
                               }
                                else
                                {
                                    //get the entire items in the document library
                                    foreach (XmlNode row in dataNode.SelectNodes("z:row", nsMgr))
                                    {
                                        //if one of the item equals "Group Verification.docx"
                                        if ((row.Attributes.GetNamedItem("ows_LinkFilename").Value).ToString() == "Group Verification.docx")
                                        {
                                            MessageBox.Show("File Found");
                                        }
                                            //no verification document has been uploaded
                                        else
                                        {
                                            MessageBox.Show("File not found");                                       
                                        }
                                    }
                                }
                            }