In order for a user to perform tasks on a SharePoint site that require higher permissions than they have, you can use "RunWithElevateedPrivileges" method of the SPSecurity object. The account used is assumed to be the "system account".
SPSecurity.RunWithElevatedPrivileges(delegate()
{
// CODE TO RUN WITH ELEVATED PRIVILEGES GOES HERE //
SPSite siteCollection = new SPSite("https://foobar.com");
SPWeb mySite = siteCollection.AllWebs["tpms/review"];
mySite.AllowUnsafeUpdates = true;
SPWeb rootSite = siteCollection.OpenWeb("/");
SPListItemCollection myList = mySite.Lists["Performance Improvement Notice Tasking"].Items;
SPListItem updateItem = myList.GetItemById((int)globalIdNumber);
updateItem["Title"] = "Foobar";
updateItem.Update();
mySite.Dispose();
rootSite.Dispose();
// END ELEVATED CODE BLOCK //
});
This mean no more .credentials auth crap.