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;
}

Solution 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))

Solution 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>

Solution 3

SelectedValue of a dropdownlist would never be null. It could be empty string, but it can never be null...

Solution 4

It would be better to set the Items in this fashion

<asp:ListItem Text="Select One" Value=""></asp:ListItem>

Also SelectedValue of the Dropdown is a string property so better check the same using string.IsNullOrEmpty as it cannot be null, leave the value blank where you want to consider it as null and repeat the same values in the Text and Value part for others

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Comments

[Com.Man.Do.Girl]

I did as you said but when I insert something in txtProductName, it not displayed in browser.

[Com.Man.Do.Girl]

@Alex Still not displayed.You see, my ddl somehow affecting textbox txtProductName. it Should display what I type in txtProductName first. Should i leave it be, and I select ddl item, then selectedValue will fill in. Or, I can leave both empty, still getting result as i want.

[Com.Man.Do.Girl]

However weird it is, my problem regarding to this question is being solved by only replacing txtProductName.Text = ""; with SqlProductmaster.InsertParameters["ProductName"].DefaultValu‌​e = txtProductName.Text; Working like charm though.