Step 1:-Add a web reference of the list that you want to access the lists are exposed through services that reside in _vt_bin folder.
step 2:-Create object of Webreference_name.Lists obj=new Webreference_name.Lists()
obj.Credentials = System.Net.CredentialCache.DefaultCredentials;
step 3:- string listName = "list_name";
string viewName = "";
string rowLimit = "150";
XmlElement query = xmlDoc.CreateElement("Query");
XmlElement viewFields = xmlDoc.CreateElement("ViewFields");
XmlElement queryOptions = xmlDoc.CreateElement("QueryOptions");
step 4:-
query.InnerXml = "<Where><Gt><FieldRef Name=\"ID\" />" +
"<Value Type=\"Counter\">1</Value></Gt></Where>";
StringBuilder fieldRef = new StringBuilder();
fieldRef.Append("<FieldRef Name=\"Field_Name\" />");
viewFields.InnerXml = fieldRef.ToString();
queryOptions.InnerXml = "<IncludeMandatoryColumns>FALSE</IncludeMandatoryColumns>";
System.Xml.XmlNode nodeListItems =
objListService.GetListItems
(listName, viewName, query, viewFields, rowLimit, queryOptions, null);
XmlDataDocument xmlDocResult = new XmlDataDocument();
xmlDocResult.LoadXml(nodeListItems.InnerXml);
XmlNodeList rows = xmlDocResult.GetElementsByTagName("z:row"); //fetching data from xmlnodelist on row basis
foreach(XmlNode attr in rows)
{
//logic
}