ASP.net DropDownList with no selected item

删除回忆录丶 提交于 2019-12-01 03:07:59

You can add an empty item to the top of your dropdownlist programmatically like this:

myDropDown.Items.Insert(0, new ListItem(string.Empty, string.Empty));
myDropDown.SelectedIndex = 0;

Not sure I understand your question but try this:

DropDownList1.ClearSelection()

or

DropDownList1.SelectedIndex = -1;

You can set the SelectedIndex property to -1 or you can add an empty entry as the first item in the data source and validate the selection on form submission.

This should work on the client side:

<asp:DropDownList ID="YourID" runat="server" DataSourceID="YourDataSource
DataTextField="Text" DataValueField="Value" AppendDataBoundItems="True">
    <asp:ListItem Text="" Selected="True"></asp:ListItem>
</asp:DropDownList>

yourDropDownList.Items.Clear()

To repopulate, you can either add items statically as per womps suggestion (substituting params in the insert() method, or you can populate it dynamically from a data source. The backing store for list items is the ListItemCollection.

Marco Castelo

If the dropdownlist is being populated by DataSource, is important do the DataBind before the insert. Otherwise the item insertion does not happen.

myDropDown.DataBind();
myDropDown.Items.Insert(0, new ListItem(string.Empty, string.Empty));
myDropDown.SelectedIndex = 0;

https://stackoverflow.com/a/2224636/1467453

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