You also need to change this function:
public DataTable GetEmployeerid()
{
string strConnection = ConfigurationManager.ConnectionStrings["MyConsString"].ConnectionString;
SqlConnection conn = new SqlConnection(strConnection);
SqlCommand cmd = new SqlCommand("Select Employeerid from Employeertable", conn);
conn.Open();
SqlDataAdapter da = new SqlDataAdapter(cmd);
DataTable dt = new DataTable();
da.Fill(dt);
return dt;
}