Show Message using Label when No data

hi 

i have search button in my page this is my behind code

protected void search_Click(object sender, ImageClickEventArgs e)
    {

        SqlConnection _cn = new SqlConnection(System.Web.Configuration.WebConfigurationManager.ConnectionStrings["behtopConnectionString"].ConnectionString);
        SqlCommand _cmd = new SqlCommand("Exec First_Search @Key", _cn);
        _cmd.Parameters.AddWithValue("@Key", txtsearch.Text);
        _cn.Open();
        SqlDataReader _dr = _cmd.ExecuteReader();
        
        if (_dr.HasRows)
        {
            DataList1.DataSource = _dr; 
            DataList1.DataBind();


        }
        _cn.Close();

   
     

    }

i have lable in my page that   Label1.Visible = false; 

I want when user click on search button if there isn't any result  == Label1.Visible = True; 

and it show my lable 

how i can do it?