button1_click event error

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C#

ASP.NET

ADO.NET

i wanted to load image from sql to asp.net page and its working when page is loaded but i want it to load when button1_click is done or when i select from dropdown list menu below is the code for button1_click and its not working please help me with this error thanks in advance for all my friends

protected void Page_Load(object sender, EventArgs e)
    {
        if (!IsPostBack)
        {
            BindFiles();
        }
    }

    protected void Button1_Click(object sender, EventArgs e)
    {
       /* if (!IsPostBack)
        {
            BindFiles();
        }*/
    }

    /// <summary>
    /// Binds the files.
    /// </summary>
    private void BindFiles()
    {
        DataTable table = new DataTable();

        SqlConnection _conn1 = new SqlConnection("Integrated Security=SSPI;Persist Security Info=False;Initial Catalog=Northwind;Data Source=KACHU-PC\\SQLEXPRESS");
        {
            string sql = "SELECT imageid, bid, pid FROM myimages Order By bid";
            using (SqlCommand cmd = new SqlCommand(sql, _conn1))
            {
                using (SqlDataAdapter ad = new SqlDataAdapter(cmd))
                {
                    ad.Fill(table);
                }
            }
        }
        GridView1.DataSource = table;
        GridView1.DataBind();
    }