getting current element id node for select

i have an xml file in my web project so i need edit some of them when user wants and i write codes like this;

publicvoid EditAnnouncement(int intAnnID,string strAnnTitle,string strAnnBody)

{

XmlDocument annDoc =newXmlDocument();

annDoc.Load(HttpContext.Current.Server.MapPath("~/App_Data/Announcement.xml"));

string xpathExpression =string.Format("//annPanel/ann[annID={0}]", intAnnID);

XmlNode ann = annDoc.SelectSingleNode(xpathExpression);

if (ann ==null)

{

thrownewException(string.Format("Element 'ann' with id ='{0}' not found"), intAnnID);

}

XmlElement annTitle = (XmlElement)ann.SelectSingleNode("annTitle");

annTitle.InnerText = strAnnTitle;

XmlElement annBody = (XmlElement)ann.SelectSingleNode("annBody");

annTitle.InnerText = strAnnBody;

annDoc.Save(HttpContext.Current.Server.MapPath("~/App_Data/Announcement.xml"));

}

but i need intannID variable from somewhere how can i get this for current node which user wants to edit?

i think that i must write a function that gets the current announcement id node innertext which user want to edit ; and set it to any variable likeabc=getID(); and after call editAnnouncement func. (EditAnnoncement(abc,bb,cc) ) but i couldnt write getID func; how can i select innertext of current announcement id ?

this is my xml;

[4753 byte] By [Radith] at [2007-12-23]