用户选择文件目录来备份数据库C＃asp.net

Question

我已经成功编写了一个按钮来将数据库备份到某个目录，但我不知道如何允许用户选择自己的备份目录。

的.aspx

<label>Backup File Name:</label>
&nbsp;<asp:textbox type="text" id="txtb" runat="server" cssclass="form-control" width="30%" />

<label>File Directory:</label>

<asp:Button ID="Button2" runat="server" OnClick="Button111_Click" Text="backup" CssClass="btn btn-success btn-lg" /> 

的.cs

protected void Button111_Click(object sender, EventArgs e)
{
    SqlCommand sqlcmd = new SqlCommand();
    SqlConnection con = new SqlConnection(ConfigurationManager.ConnectionStrings["mycon"].ToString());

    string backupDIR = "C:\\backup";
    if (!System.IO.Directory.Exists(backupDIR))
    {
        System.IO.Directory.CreateDirectory(backupDIR);
    }
    try
    {
        con.Open();
        sqlcmd = new SqlCommand(
            "backup database iporma to disk= '" + backupDIR + "\\"+txtb.Text+"" + DateTime.Now.ToString("ddMMyy_HHss") + ".bak'", con);
        sqlcmd.ExecuteNonQuery();
        con.Close();
        lblError.Text = "Completed backup file  located C:\\backup";
    }
    catch (Exception ex)
    {
        lblError.Text = "Error" + ex.ToString();
    }
}