Programmatically Select Multiple Items of an ASP.NET ListBox

In one of the forums, a user recently asked how to select multiple items of an ASP.NET ListBox. Here’s how

<div>
    <asp:ListBox ID="ListBox1" runat="server">
        <asp:ListItem Value="One" />
        <asp:ListItem Value="Two" />
        <asp:ListItem Value="Three" />
        <asp:ListItem Value="Four" />
        <asp:ListItem Value="Five" />
    </asp:ListBox>
</div>    

C#

protected void Page_Load(object sender, EventArgs e)
{
    ListBox1.SelectionMode = ListSelectionMode.Multiple;
    for (int i = 0; i < ListBox1.Items.Count; i++)
    {
        if(i == 0 || i == 2 || i == 4)
        {
            ListBox1.Items[i].Selected = true;
        }
    }
}

VB.NET

Protected Sub Page_Load(ByVal sender As Object, ByVal e As EventArgs)
    ListBox1.SelectionMode = ListSelectionMode.Multiple
    For i As Integer = 0 To ListBox1.Items.Count - 1
        If i = 0 OrElse i = 2 OrElse i = 4 Then
            ListBox1.Items(i).Selected = True
        End If
    Next i
End Sub

The code shown above selects the first, third and fifth items of a ListBox as in the screenshot below

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About The Author

Suprotim Agarwal, ASP.NET Architecture MVP works as an Architect Consultant and provides consultancy on how to design and develop Web applications.

Suprotim is also the founder and primary contributor to DevCurry, DotNetCurry and SQLServerCurry. He has also written an EBook 51 Recipes using jQuery with ASP.NET Controls.

Follow him on twitter @suprotimagarwal