DropDownList returning NULL

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C#

ASP.NET

I have a DDL that is bound to a SQL Server table depending on the selection of another DDL and inserting text into a Label depending on the selection. The problem is that the label is either not getting the data or the DDL are providing NULL to the label. Please check my code below and help resolve. Thank you.

protected void Page_Load(object sender, EventArgs e)
    {
        if(DropDownList1.SelectedIndex > 0)
        BindDropDownList2(DropDownList1.SelectedItem.Text);
    }

    protected void Button2_Click(object sender, EventArgs e)
    {
           if (DropDownList1.SelectedIndex == 5)
                if (DropDownList2.SelectedIndex == 3)
                       Label1.Text = "You selected index 5 from ddl1 and index 3 from ddl2";

    }

private void BindDropDownList2(string field)
    {
        if (DropDownList1.SelectedIndex != 5)
        {
            con.ConnectionString = strcon;
            com.Connection = con;
            con.Open();

            string strQuery = @"SELECT " + DropDownList1.SelectedItem.Text + " FROM NUMS";
            da = new SqlDataAdapter(strQuery, con);
            da.Fill(ds);

            DropDownList2.DataSource = ds;
            DropDownList2.DataTextField = field;
            DropDownList2.DataValueField = field;
            DropDownList2.DataBind();

            con.Close();
        }
        else
        {
            DropDownList2.Items.Clear();
            DropDownList2.Items.Add("");
            DropDownList2.Items.Add("A");
            DropDownList2.Items.Add("B");
        }
    }