[Solved] Session Data is shared between different users in ASP.Net

Sir good morning

Sir multiple users are logined into the system but some time data is getting mixed up each other.

As example three uses are making receipt but suddenly one user close the aspx page forcefully or logout, now second user want to save the receipt but customer name and invoice changed automatically as per first user. 

please help me to avoid this problem

Thank you sir.

/// <summary>
/// Summary description for MainClass
/// </summary>
public class MainClass
{
    SqlConnection SqlCn;
    SqlCommand SqlCm;
    SqlDataReader SqlDr;
    SqlDataAdapter SqlDa;
    ConnectionState ConState;
 
    public static string SqlQryClass;
    public static string ConPathClass;
    public static string ConString;
    public static Boolean SmtpContectionStatusClass;
    // End Connection and Sql Class
 
 
    public static string FormEntryLevelClass;
    public static string FormModifyLevelClass;
    public static string FormReportLevelClass;
    public static string FormReportExportLevelClass;
    public static int FormNoClass;
    public static int SpecialPermissionNoClass;
    public static string SpecialPermissionNameClass;
    public static int ModuleNoClass;
 
    // End Form Vaiable
    public static int MainCompanyCodeClass;
    public static string MainCompanyNameClass;
    public static string MainCompanyNickClass;
    public static string MainCompanyTypeClass;
    public static string CompanyActiveStatusClass;
    public static string StdDatabaseNameClass;
    public static string FullCompanyNameClass;
    public static string SalesCurrencyNameClass;
    public static string SalesCurrencyNameSecondClass;
    public static string ServiceCurrencyNameClass;
    public static string ServiceCurrencyNameSecondClass;
    public static string CountryNameShortClass;
    public static string CountryNameFullClass;
    public static string CountryPhoneStdClass;
    public static string LessPaymentLimitClass;
    public static string CompanyTinNoClass;
    public static string CompanyRcNoClass;
    public static string CostingMethodClass;

    //...........
}