mvc 4 error " Non-static method requires a target."

mvc 4 error " Non-static method requires a target."

public ActionResult returnbook(string id)
{
tblIssuedbook issue = db.tblIssuedbooks.Single(r => r.AccessionNo
== id);
return View(issue);
}
[HttpPost]
public ActionResult returnbook(tblIssuedbook issue)
{
tblIssuedbook ib = (from r in db.tblIssuedbooks where
r.AccessionNo == issue.AccessionNo select r).FirstOrDefault();
ib.AccessionNo = issue.AccessionNo;
ib.Name = issue.Name;
ib.IssueDate = issue.IssueDate;
ib.DueDate = issue.DueDate;
ib.Type = issue.Type;
ib.MemberId = issue.MemberId;
ib.SubmittDate = issue.SubmittDate;
ib.Status = issue.Status;
db.SaveChanges();
return View();
}