using (SPSite site = new SPSite("http://aissp2013/sites/Team"))
{
    SPWeb web = site.RootWeb;
    SPList list = web.Lists["Employees"];
    SPListItem item = list.GetItemById(1);
    item.Properties.Add("Employee Name", "Nadeem Yousuf");
    item.Update();
    list.Update();
}