How To Create A Custom SQL Statement.

im creating a custom sql statement where my code starts like tt.. its a double query and how do i link the 2nd part to the first part (select * from PO where 1=1)?

<script runat="server">
   
      
 
    protected void CheckBox1_CheckedChanged(object sender, EventArgs e)
    {
        strquery += " and PO between " + textbox1.text + " and " + textbox2.text;
    }

    protected void CheckBox2_CheckedChanged(object sender, EventArgs e)
    {
        strquery += " and Dlvdate between " + textbox3.text + " and " + textbox4.text;
    }
</script>
 
 im a serious newbie with C#