fill gridview using listbox multiple value selection

<asp:ListBox ID="ListBox1" runat="server" SelectionMode="Multiple">

<asp:ListItem Selected="True" Value="1">a</asp:ListItem>

<asp:ListItem Selected="True" Value="2">b</asp:ListItem>

<asp:ListItem Value="3">n</asp:ListItem>

</asp:ListBox>
 


var selected = ListBox1.GetSelectedIndices().ToList();

var selectedValues = (from c in selected select ListBox1.Items[c].Value).ToList();



Now you can use selectedValues to populate your grid