How to encrypt and decrypt XML File data in ASP.Net

XML

<?xml version="1.0" standalone="yes"?>
<Users>
  <User>
    <Username>Mudassar</Username>
    <Password>Ao5ZnFYo344iWqv/Jr9euw==</Password>
  </User>
  <User>
    <Username>Ravi</Username>
    <Password>4rAIjA6LNuLd0kV7rYjTKQ==</Password>
  </User>
  <User>
    <Username>Joseph</Username>
    <Password>yCJzArS8YHJWprAmiBIJ9Q==</Password>
  </User>
  <User>
    <Username>Kaldon</Username>
    <Password>BarzPZWhqD7TeO7TSYwHbg==</Password>
  </User>
</Users>

HTML

<table border="0" cellpadding="0" cellspacing="0">
        <tr>
            <td>
                Username:
            </td>
            <td>
                <asp:TextBox ID="txtUsername" runat="server" Text="" />
            </td>
        </tr>
        <tr>
            <td>
                Password:
            </td>
            <td>
                <asp:TextBox ID="txtPassword" runat="server" TextMode="Password" />
            </td>
        </tr>
        <tr>
            <td>
            </td>
            <td>
                <asp:Button ID="btnSubmit" OnClick="Submit" Text="Submit" runat="server" />
            </td>
        </tr>
    </table>
    <hr />
    <asp:GridView ID="gvUsers" runat="server" AutoGenerateColumns="false" HeaderStyle-BackColor="#3AC0F2"
        HeaderStyle-ForeColor="White" RowStyle-BackColor="#A1DCF2" OnRowDataBound="OnRowDataBound">
        <Columns>
            <asp:BoundField DataField="Username" HeaderText="Username" />
            <asp:BoundField DataField="Password" HeaderText="Encrypted Password" />
            <asp:BoundField DataField="Password" HeaderText="Decrypted Password" />
        </Columns>
    </asp:GridView>

Code

using System.IO;
using System.Text;
using System.Data;
using System.Security.Cryptography;

protected void Page_Load(object sender, EventArgs e)
{
    if (!this.IsPostBack)
    {
        using (DataSet ds = new DataSet())
        {
            ds.ReadXml(Server.MapPath("~/XML/Users.xml"));
            gvUsers.DataSource = ds;
            gvUsers.DataBind();
        }
    }
}

protected void OnRowDataBound(object sender, GridViewRowEventArgs e)
{
    if (e.Row.RowType == DataControlRowType.DataRow)
    {
        e.Row.Cells[2].Text = Decrypt(e.Row.Cells[2].Text);
    }
}

protected void Submit(object sender, EventArgs e)
{
    using (DataSet ds = new DataSet())
    {
        ds.ReadXml(Server.MapPath("~/XML/Users.xml"));
        ds.Tables[0].Rows.Add(txtUsername.Text.Trim(), Encrypt(txtPassword.Text.Trim()));
        ds.WriteXml(Server.MapPath("~/XML/Users.xml"));
    }
    Response.Redirect(Request.Url.AbsoluteUri);
}

private string Encrypt(string clearText)
{
    string EncryptionKey = "MAKV2SPBNI99212";
    byte[] clearBytes = Encoding.Unicode.GetBytes(clearText);
    using (Aes encryptor = Aes.Create())
    {
        Rfc2898DeriveBytes pdb = new Rfc2898DeriveBytes(EncryptionKey, new byte[] { 0x49, 0x76, 0x61, 0x6e, 0x20, 0x4d, 0x65, 0x64, 0x76, 0x65, 0x64, 0x65, 0x76 });
        encryptor.Key = pdb.GetBytes(32);
        encryptor.IV = pdb.GetBytes(16);
        using (MemoryStream ms = new MemoryStream())
        {
            using (CryptoStream cs = new CryptoStream(ms, encryptor.CreateEncryptor(), CryptoStreamMode.Write))
            {
                cs.Write(clearBytes, 0, clearBytes.Length);
                cs.Close();
            }
            clearText = Convert.ToBase64String(ms.ToArray());
        }
    }
    return clearText;
}

private string Decrypt(string cipherText)
{
    string EncryptionKey = "MAKV2SPBNI99212";
    byte[] cipherBytes = Convert.FromBase64String(cipherText);
    using (Aes encryptor = Aes.Create())
    {
        Rfc2898DeriveBytes pdb = new Rfc2898DeriveBytes(EncryptionKey, new byte[] { 0x49, 0x76, 0x61, 0x6e, 0x20, 0x4d, 0x65, 0x64, 0x76, 0x65, 0x64, 0x65, 0x76 });
        encryptor.Key = pdb.GetBytes(32);
        encryptor.IV = pdb.GetBytes(16);
        using (MemoryStream ms = new MemoryStream())
        {
            using (CryptoStream cs = new CryptoStream(ms, encryptor.CreateDecryptor(), CryptoStreamMode.Write))
            {
                cs.Write(cipherBytes, 0, cipherBytes.Length);
                cs.Close();
            }
            cipherText = Encoding.Unicode.GetString(ms.ToArray());
        }
    }
    return cipherText;
}