object reference not set to any instant exception

[shahidrasul]

hi

i have a object to a user defined class which properly intialized from class when first form load, but after post back it loose reference and such error occured

[NullReferenceException: Object reference not set to an instance of an object.]
monthlyreport.GetReport() in c:\Time Entry System\WebTimeEntrySystem\monthlyreport.aspx.cs:10 0
monthlyreport.btn_show_report_Click(Object sender, EventArgs e) in c:\Time Entry System\WebTimeEntrySystem\monthlyreport.aspx.cs:94
System.Web.UI.WebControls.Button.OnClick(EventArgs e) +105
System.Web.UI.WebControls.Button.RaisePostBackEven t(String eventArgument) +107
System.Web.UI.WebControls.Button.System.Web.UI.IPo stBackEventHandler.RaisePostBackEvent(String eventArgument) +7
System.Web.UI.Page.RaisePostBackEvent(IPostBackEve ntHandler sourceControl, String eventArgument) +11
System.Web.UI.Page.RaisePostBackEvent(NameValueCol lection postData) +33
System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint) +5102

My c# code is

using System;
using System.Data;
using System.Configuration;
using System.Collections;
using System.Web;
using System.Web.Security;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Web.UI.WebControls.WebParts;
using System.Web.UI.HtmlControls;
using System.Data.SqlClient;
using TimeEntrySystem;
using TimeEntrySystem.BLL;
 
public partial class dailyreport : System.Web.UI.Page
{
    private DataTable objDataTable;
    private Reports objReport;
 
    protected void btn_show_report_Click(object sender, EventArgs e)
    {
        DateTime startingDate = Convert.ToDateTime(tb_daily_report_date.Text);
 
        #region
        btn_daily_report_show.Enabled = false;
        DailyReport(startingDate);
        btn_daily_report_show.Enabled = true;
        #endregion
    }
 
    public void DailyReport(DateTime startingDate)
    {
        objDataTable =  objReport.ReturnDailyReport(startingDate);
        if (objDataTable == null)
        {
            lb_daily_report_error.Text = "There is some error in record reports.";
        }
        if (objDataTable.Rows.Count == 0)
        {
            lb_daily_report_error.Text = "No Record found.";
            objDataTable.Clear();
            return;
        }
    }
 
    public DataTable ObjDataTable
    {
        get { return objDataTable; }        
    }
    protected void Page_Load(object sender, EventArgs e)
    {        
        if (!IsPostBack)
        {
            objDataTable = new DataTable("DailyReports");
            objReport = new Reports();
 
            DateTime startingDate = DateTime.Now.Date;
            tb_daily_report_date.Text = startingDate.Date.ToShortDateString();            
            DailyReport(startingDate);
        }
        lb_report_duration1.Text = "Daily Report";
        lb_report_duration2.Text = tb_daily_report_date.Text;
 
        vld_range_daily_report_tb_start_date.MinimumValue = objReport.GetMinDate().ToShortDateString();
        vld_range_daily_report_tb_start_date.MaximumValue = DateTime.Now.ToShortDateString();
 
    }
    protected void start_img_Click(object sender, ImageClickEventArgs e)
    {
        tb_daily_report_date.Text = cld_tb_daily_report_date.SelectedDate.Value.ToString();
    }
}

after post objReport and objTable loose its reference from their classes

so please any body help me about that problem thanks

[Plater]

The error says it occurs on the monthlyreport page, yet you have shown code for the dailyreport page. Do you have a monthly report page you could show us code for?

[shahidrasul]

The error says it occurs on the monthlyreport page, yet you have shown code for the dailyreport page. Do you have a monthly report page you could show us code for?

sorry man my fault i replace the code of daily report ....
but error is same in daily report page and monthly report page this is monthly report page

using System;
using System.Data;
using System.Configuration;
using System.Collections;
using System.Web;
using System.Web.Security;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Web.UI.WebControls.WebParts;
using System.Web.UI.HtmlControls;
using TimeEntrySystem.BLL;
using System.Collections.Generic;
 
public partial class monthlyreport : System.Web.UI.Page
{
    private Reports objReport;
    private IList<Employee> lstEmployee;
    private Employee objEmployee;
    private IList<int> lstYear;
    private IList<string> lstMonth;
    private DataTable objDataTable;
 
    protected void Page_Load(object sender, EventArgs e)
    {
 
        if (Session["user_id"] == null)
        {
            Response.Redirect("login.aspx");
        }        
 
        if (!IsPostBack)
        {
            objReport = new Reports();
            lstEmployee = new List<Employee>();
            objEmployee = new Employee();
            lstYear = new List<int>();
            lstMonth = new List<string>();
            objDataTable = new DataTable();
 
            lstEmployee = objReport.GetAllEmployeesRegistered();
            lstYear = objReport.GetAllYearsRegistered();
 
            objEmployee.Employee_Name = "All";
            objEmployee.UserId = "All";
            lstEmployee.Insert(0, objEmployee);
 
            foreach (Employee item in lstEmployee)
            {
                dpl_monthly_report_user_id.Items.Add(item.Employee_Name);
            }
            dpl_monthly_report_user_id.SelectedIndex = 0;
 
            if (lstYear.Count > 0)
            {
                lstMonth = objReport.GetMonthsRegistered(lstYear[lstYear.Count - 1]);
            }
            else
            {
                return;
            }
 
            foreach (int item in lstYear)
            {
                dpl_monthly_report_year.Items.Add(item.ToString());
            }
            dpl_monthly_report_year.SelectedIndex = lstYear.Count - 1;
 
            foreach (string item in lstMonth)
            {
                dpl_monthly_report_month.Items.Add(item);
            }
 
            if (lstMonth.Count > 0)
            {
                dpl_monthly_report_month.SelectedIndex = lstMonth.Count-1;
            }            
            GetReport();
        }
    }
    protected void dpl_year_SelectedIndexChanged(object sender, EventArgs e)
    {
        lstMonth = objReport.GetMonthsRegistered(Convert.ToInt32(dpl_monthly_report_year.SelectedValue));
        dpl_monthly_report_month.Items.Clear();
        foreach(string item in lstMonth)
        {
            dpl_monthly_report_month.Items.Add(item);
        }
        dpl_monthly_report_month.SelectedIndex = lstMonth.Count-1;
        GetReport();       
    }
    protected void btn_show_report_Click(object sender, EventArgs e)
    {        
        btn_monthly_report_show_report.Enabled = false;
        GetReport();
        btn_monthly_report_show_report.Enabled = true;        
    }
 
    public void GetReport()
    {
        objDataTable.Clear();
        objDataTable = objReport.ReturnMothlyReportDataTable(Convert.ToInt32(dpl_monthly_report_year.SelectedValue), dpl_monthly_report_month.SelectedValue.ToString(), lstEmployee[dpl_monthly_report_user_id.SelectedIndex].UserId);
 
        if (objDataTable == null)
        {
            lb_monthly_report_error.Text = "There is some error in reports.";
        }
        if (objDataTable.Rows.Count == 0)
        {
            lb_monthly_report_error.Text = "No Record found.";
        }
    }
 
    public DataTable ObjDataTable
    {
        get { return objDataTable; }
    }    
}

[Curtis Rutland]

shahidrasul, please use code tags when you post [code] tags when you post code. It makes code much easier for us to read, and if we can't read it, we can't help. You can click the # button in the text editor to add the tags for you.

MODERATOR

[Plater]

Well I see this code:

if (objDataTable == null)
        {
            lb_monthly_report_error.Text = "There is some error in reports.";
        }
        if (objDataTable.Rows.Count == 0)
        {
            lb_monthly_report_error.Text = "No Record found.";
        }
 

Now you are checking for null, which is good, but if it IS null, the second check is still being attempted, and could result in the error you are seeing.

Also, anthing in this line:
objDataTable = objReport.ReturnMothlyReportDataTable(Convert.ToIn t32(dpl_monthly_report_year.SelectedValue), dpl_monthly_report_month.SelectedValue.ToString(), lstEmployee[dpl_monthly_report_user_id.SelectedIndex].UserId);

could also cause the error if one of them were null