How to Read File From Directory Asp.net c#

protected void BindGridview()
    {        
        string[] filesPath = Directory.GetFiles(@"D:\abc\abc\" + textbox1.Text);
        List<listitem> files = new List<listitem>();
        foreach (string path in filesPath)
        {
            files.Add(new ListItem(Path.GetFileName(path)));
        }
        GridView1.DataSource = files;
        GridView1.DataBind();
       }
<asp:TextBox ID="txtFormnum" runat="server">
        <asp:Button ID="btnsrch" runat="server" Text="Search" OnClick="btnsrch_Click1" />
        <asp:GridView ID="GridView1" runat="server">
protected void btnsrch_Click1(object sender, EventArgs e)
    {
        BindGridview();
    }