C# how to set dropDownList default value for selectedValue = null

Question

I have a dropdownlist1 that has has 6 collection items including Select One. What I want is this ddl is set to Selectedvalue = null. But what I am getting is my ddl always selecting Select One as its initial value. My ddl properties for Select One is selected:false. How to set this ddl to initial selected value = null?

<asp:DropDownList ID="DropDownList1" runat="server" Visible="False" Width="146px">
     <asp:ListItem>Ceiling Speaker</asp:ListItem>
     <asp:ListItem>Remote Microphone</asp:ListItem>
     <asp:ListItem>Digital Source Player</asp:ListItem>
     <asp:ListItem>Remote paging Console</asp:ListItem>
     <asp:ListItem>Modular Mixer</asp:ListItem>
     <asp:ListItem>Select One</asp:ListItem>
</asp:DropDownList>


if (String.IsNullOrEmpty(txtSearchProductname.Text))
{
   if (DropDownList1.SelectedValue == null)
   {
       txtProductName.Text = "";
   }
   else
   {
       SqlProductmaster.InsertParameters["ProductName"].DefaultValue = DropDownList1.SelectedValue.ToString();
   }
}
else
{
    SqlProductmaster.InsertParameters["ProductName"].DefaultValue = txtProductName.Text;
}

Answer 1

You can add an 'Empty' value item:

<asp:DropDownList ID="DropDownList1" runat="server" Width="146px">
    <asp:ListItem Selected="True"></asp:ListItem>
    <asp:ListItem>Ceiling Speaker</asp:ListItem>
    <asp:ListItem>Remote Microphone</asp:ListItem>
    <asp:ListItem>Digital Source Player</asp:ListItem>
    <asp:ListItem>Remote paging Console</asp:ListItem>
    <asp:ListItem>Modular Mixer</asp:ListItem>
    <asp:ListItem>Select One</asp:ListItem>
</asp:DropDownList>

Then you would check for

if (string.IsNullOrEmpty(DropDownList1.SelectedValue))

Answer 2

<asp:DropDownList ID="DropDownList1" AppendDataBoundItems="true" runat="server"> 
    <asp:ListItem Text="(Select a State)" Value="" />   
    <asp:ListItem>Ceiling Speaker</asp:ListItem>
    <asp:ListItem>Remote Microphone</asp:ListItem>
    <asp:ListItem>Digital Source Player</asp:ListItem>
    <asp:ListItem>Remote paging Console</asp:ListItem>
    <asp:ListItem>Modular Mixer</asp:ListItem>
    <asp:ListItem>Select One</asp:ListItem>    
</asp:DropDownList>