ASP.NET

<page enableEventValidation="false">

The state information is invalid for this page and might be corrupted. 
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.Web.HttpException: The state information is invalid for this page and might be corrupted.

Source Error: 


[No relevant source lines]
 

Source File: c:\WINDOWS\Microsoft.NET\Framework\v2.0.50727\Temporary ASP.NET Files\portal9161new\1f521660\5181c4db\App_Web_mryexrix.10.cs    Line: 0 

Stack Trace: 


[FormatException: Invalid character in a Base-64 string.]
   System.Convert.FromBase64String(String s) +0
   System.Web.UI.ObjectStateFormatter.Deserialize(String inputString) +72
   System.Web.UI.ObjectStateFormatter.System.Web.UI.IStateFormatter.Deserialize(String serializedState) +4
   System.Web.UI.ClientScriptManager.EnsureEventValidationFieldLoaded() +57

[ViewStateException: Invalid viewstate. 
	Client IP: 127.0.0.1
	Port: 
	User-Agent: Mozilla/4.0 (compatible; MSIE 7.0; Windows NT 5.1; InfoPath.2; .NET CLR 2.0.50727; .NET CLR 3.0.04506.648; .NET CLR 3.5.21022; .NET CLR 3.0.4506.2152; .NET CLR 3.5.30729; MSN Optimized;US)
	ViewState: /wEWFwLO08XUCALz3vPHCwKzrv6wAwK9vJ38DAKpi4ufBQKIgpWfBQLrmZefBQLKkICfBQK98JOfBQKc5/2WBQL//veWBQLe9YifBQLj4JT2BwLUk/WqAgKOkrn2CAKLkrn2CALCvJnnBAK//ZjtBwLNzIK2CALsjZ7JCALgutCTDwKLlba1BgLBzqW+BXf/jiRHAjSf0ntN+9hIlN0OfE3b,/wEWEQKIr8XKBALE5ML0AgLl97ftDQLb44SECwLb4+iFCwLR5JWQCwKBp/mABQL3meq7DgLqwoebCwL14vPbCQKe5MqPCQKNo6XnBAKe8IG6DAKipuWCDAK33sGJAQK33rWJAQLk97ftDfQ62Og2DDwFHqA1OfwvN70aZODt
	Referer: http://localhost:4424/Portal9161new/seatingplan.aspx
	Path: /Portal9161new/seatingplan.aspx]

protected void GridView1_RowDataBound(object sender, GridViewRowEventArgs e)
{
    GridViewRow gv ;
    gv =GridView1.SelectedRow;
    if (gv.Cells[4].Text == "KS" || gv.Cells[5].Text<=5)
    {
        if (gv.RowType == DataControlRowType.DataRow)
        {
            CheckBox chkDelete = (CheckBox)gv.Cells[0].Controls[0];
            chkDelete.Enabled = false;
        }
    }

}