Download files from Folder (Directory) on modal popup in ASP.Net using C# and VB.Net

Hi Vanessa,

Refer below sample.

HTML

<asp:Button ID="btnShowPopup" runat="server" Text="Show Popup" />
<div id="dialog" style="display: none">
    <asp:GridView ID="GridView1" runat="server" AutoGenerateColumns="false" EmptyDataText="No files uploaded">
        <Columns>
            <asp:BoundField DataField="Text" HeaderText="File Name" />
            <asp:TemplateField>
                <ItemTemplate>
                    <asp:LinkButton ID="lnkDownload" Text="Download" CommandArgument='<%# Eval("Value") %>'
                        runat="server" OnClick="DownloadFile"></asp:LinkButton>
                </ItemTemplate>
            </asp:TemplateField>
        </Columns>
    </asp:GridView>
</div>
<script type="text/javascript" src="https://code.jquery.com/jquery-1.12.4.js"></script>
<link rel="stylesheet" href="https://code.jquery.com/ui/1.12.1/themes/base/jquery-ui.css" />
<script type="text/javascript" src="https://code.jquery.com/ui/1.12.1/jquery-ui.js"></script>
<script type="text/javascript">
    $(function () {
        $("[id*=btnShowPopup]").click(function () {
            $("#dialog").dialog({
                title: "File Details",
                width: 250,
                buttons: {
                    Ok: function () {
                        $(this).dialog('close');
                    }
                },
                modal: true
            });
            return false;
        });
    });
</script>

Code

C#

protected void Page_Load(object sender, EventArgs e)
{
    if (!IsPostBack)
    {
        string[] filePaths = System.IO.Directory.GetFiles(Server.MapPath("~/Files/"));
        List<ListItem> files = new List<ListItem>();
        foreach (string filePath in filePaths)
        {
            files.Add(new ListItem(System.IO.Path.GetFileName(filePath), filePath));
        }
        GridView1.DataSource = files;
        GridView1.DataBind();
    }
}

protected void DownloadFile(object sender, EventArgs e)
{
    string filePath = (sender as LinkButton).CommandArgument;
    Response.ContentType = ContentType;
    Response.AppendHeader("Content-Disposition", "attachment; filename=" + System.IO.Path.GetFileName(filePath));
    Response.WriteFile(filePath);
    Response.End();
}

VB.Net

Protected Sub Page_Load(ByVal sender As Object, ByVal e As EventArgs) Handles Me.Load
    If Not IsPostBack Then
        Dim filePaths As String() = IO.Directory.GetFiles(Server.MapPath("~/Files/"))
        Dim files As List(Of ListItem) = New List(Of ListItem)()
        For Each filePath As String In filePaths
            files.Add(New ListItem(IO.Path.GetFileName(filePath), filePath))
        Next
        GridView1.DataSource = files
        GridView1.DataBind()
    End If
End Sub

Protected Sub DownloadFile(ByVal sender As Object, ByVal e As EventArgs)
    Dim filePath As String = TryCast(sender, LinkButton).CommandArgument
    Response.ContentType = ContentType
    Response.AppendHeader("Content-Disposition", "attachment; filename=" & IO.Path.GetFileName(filePath))
    Response.WriteFile(filePath)
    Response.End()
End Sub

Screenshot