Object reference not set to an instance of an object

hi,

In my application getting above exception for first  time submit.
   string strSPmain = "testinsert";
        SqlCommand sqlCmd = new SqlCommand();
        sqlCmd.Connection = sqlConn;
        sqlCmd.CommandType = CommandType.StoredProcedure;
        sqlCmd.CommandText = strSPmain;
        sqlCmd.Parameters.AddWithValue("@EmpID", Session["TSID"].ToString());//exeception
        sqlCmd.Parameters.AddWithValue("@ClientID", SqlDbType.Int).Value = client;
        sqlCmd.Parameters.AddWithValue("@date", SqlDbType.DateTime).Value = date;
        sqlCmd.Parameters.AddWithValue("@day", day);
 private int IDGet(DateTime startDate)
    {
        int timeSheetID = 0;
        string Connection = System.Configuration.ConfigurationManager.ConnectionStrings["abc"].ConnectionString;
        SqlConnection sqlConn = new SqlConnection(Connection);
        sqlConn.Open();
        try
        {
            string strSP = "SP_Test123_insert_get";
           // string strSP = "SP_AAEmpTSDatesINGet";
            SqlCommand sqlCmd = new SqlCommand();
            sqlCmd.Connection = sqlConn;
            sqlCmd.CommandType = CommandType.StoredProcedure;
            sqlCmd.CommandText = strSP;

            sqlCmd.Parameters.AddWithValue("@empName", txt_EmpName.Text);
            sqlCmd.Parameters.AddWithValue("@tsStartDate", startDate);
            sqlCmd.Parameters.AddWithValue("@tsEnddate", startDate.AddDays(6));


            SqlDataReader dr;
            dr = sqlCmd.ExecuteReader();
            while (dr.Read())
            {
                Session["TSID"] = dr["TSID"].ToString();
                timeSheetID = Convert.ToInt16(dr["TSID"].ToString());
            }

        }
        catch (Exception ex)
        {
        }
        finally
        {
            sqlConn.Close();
        }
        return timeSheetID;
    }

ALTER PROCEDURE [dbo].[SP_Test123_insert_get]
	-- Add the parameters for the stored procedure here
	@empName varchar(50),
    @clientId int,
	@tsStartDate datetime,
	@tsEnddate datetime  
AS
BEGIN


if exists
	(SELECT TSID from EmpAssociarTSDates nolock where EmpName = @empName and StartDate = @tsStartDate and clientID=@clientId )
begin 
SELECT TSID from EmpAssociarTSDates nolock where EmpName = @empName and StartDate = @tsStartDate and clientID=@clientId  
end
else
begin 
insert into EmpAssociarTSDates (EmpName,ClientID, StartDate, EndDate) values (@empName,@clientId, @tsStartDate, @tsEnddate)
--SELECT TSID ,ClientID from EmpAssociarTSDates nolock where EmpName = @empName and StartDate = @tsStartDate and clientID=@clientId 
 
END
End

ALTER PROCEDURE [dbo].[testinsert]
	-- Add the parameters for the stored procedure here
@EmpID int,
@ClientID int,
@EmpName varchar(50),
@StartDate datetime,
@EndDate datetime,
@date datetime,
@day varchar(50),
@Service nvarchar(max),
@Project varchar(50),
@StartTime varchar(50),
@EndTime varchar(50),
@Lunch varchar(50),
@DailyTotal varchar(50),
@Total varchar(50),
@StandardHrs varchar(50),
@OvertimeHrs varchar(50)
AS


if exists (select * from EmpAssociarTimeSheet where EmpID=@EmpID and date=@date )

begin
update EmpAssociarTimeSheet set Service=@Service,Project=@Project,StartTime=@StartTime,EndTime=@EndTime,Lunch=@Lunch,DailyTotal=@DailyTotal,
Total=@Total,StandardHrs=@StandardHrs,OvertimeHrs=@OvertimeHrs where EmpID=@EmpID and date=@date and ClientID=@ClientID

end
else
BEGIN
	insert into EmpAssociarTimeSheet(EmpID,EmpName,ClientID,StartDate,EndDate,date,day,Service,Project,StartTime,EndTime,Lunch,DailyTotal,Total,StandardHrs 
,OvertimeHrs
) values (@EmpID,@EmpName,@ClientID,@StartDate,@EndDate,@date,@day,@Service,@Project,@StartTime,@EndTime,@Lunch,@DailyTotal,@Total,@StandardHrs ,
@OvertimeHrs
)

END