private void Page_upload(string page_name)
{
	System.IO.StringWriter swrTarget = new System.IO.StringWriter();
	Server.Execute(page_name,swrTarget);
	Panel1.Controls.Add(new LiteralControl(swrTarget.ToString()));
}

Invalid character in a Base-64 string. 
Description: An unhandled exception occurred during the execution of the current web request. Please review the stack trace for more information about the error and where it originated in the code. 

Exception Details: System.FormatException: Invalid character in a Base-64 string. 

Source Error: 

An unhandled exception was generated during the execution of the current web request. Information regarding the origin and location of the exception can be identified using the exception stack trace below. 

Stack Trace: 


[FormatException: Invalid character in a Base-64 string.] 
System.Convert.FromBase64String(String s) +0 
System.Web.UI.LosFormatter.Deserialize(String input) 
System.Web.UI.Page.LoadPageStateFromPersistenceMedium() 

[HttpException (0x80004005): Invalid_Viewstate 
Client IP: 127.0.0.1 
Port: 1364 
User-Agent: Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.1; SV1; .NET CLR 1.1.4322) 
ViewState: ... 
Http-Referer: http://localhost/Opora_Net/MainForm.aspx 
Path: /Opora_Net/MainForm.aspx.] 
System.Web.UI.Page.LoadPageStateFromPersistenceMedium() 
System.Web.UI.Page.LoadPageViewState() 
System.Web.UI.Page.ProcessRequestMain()