Here is a method to add an item to the quick launch in C#
private void AddNodeToQuickLaunch(string linkName, string SiteToOpen, string pathtoPage)
{
try
{
using (SPWeb web = SPContext.Current.Site.OpenWeb(SiteToOpen))
{
web.AllowUnsafeUpdates = true;
SPNavigationNodeCollection nodes = web.Navigation.QuickLaunch;
SPNavigationNode createNode = new SPNavigationNode(linkName, pathtoPage, true);
foreach (SPNavigationNode node in nodes)
{
bool nodeExists = false;
if (node.Title.Equals("Lists"))
{
foreach (SPNavigationNode child in node.Children)
{
if (child.Title == linkName)
{
nodeExists = true;
}
}
if (!nodeExists)
{
node.Children.Add(createNode, node);
}
}
}
web.AllowUnsafeUpdates = false;
}
}
catch (Exception ex)
{
throw ex;
}
}