Update

string conString = GetConnectionString();
SqlConnection con = new SqlConnection(conString);
con.Open();
string sql = "UPDATE HumanResources.Employee SET ContactID = "+custObj.ContactID+", ManagerID = "+custObj.ManagerID+" WHERE EmployeeID = " + ID;
SqlCommand cmd = new SqlCommand(sql, con);
cmd.ExecuteNonQuery();
con.Close();