decrypt the viewstate in the asp.net

I like this view state decoder. Very easy to use.

http://ignatu.co.uk/ViewStateDecoder.aspx

The question is very tricky.
Before I go into details, first need to know what is view state.
In brief, ViewState is a Base64 encoded string and is not readable by the human eye. Though it is not difficult to decode is and read the view state information.

Open any page in a browser, go to the source page, copy the view state value in the clipboard.

Now create a page and add a hiddencontrol,

<asp:textbox id="txt_viewstate" value="{paste from clipboard}" runat="server" xmlns:asp="#unknown"></asp:textbox>

Now add a button control and write the button event

//code behind    
protected void Button1_Click(object sender, EventArgs e)
    {
        byte[] decode = Convert.FromBase64String(txt_viewstate.Text);
        Response.Write(System.Text.Encoding.ASCII.GetString(decode));
    }

Hope this helps.
cheers