thanks Bonnie Berent
just i have changed my source as below. but i am confused ,when i am create a new procedure for sub do while it work fine .please see the following syntax and suggest me why it is working like this

    Private Sub sendtoWeekOffdays(ByVal Type_name As String, ByVal myproc As String, ByVal weelyoff As Decimal)
        Dim pf As ProviderFactory = New ProviderFactory
        pf.Provider = SqlDataBase.ConnectionType
        Dim myconn As IDbConnection = pf.CreateConnection(dssToolKit.myfunc.Appvaribales.ConnectionString)
        myconn.Open()

        Dim cmd As IDbCommand = pf.CreateCommand(myproc, myconn)
        cmd.CommandType = CommandType.StoredProcedure

        Dim params As IDbDataParameter
        params = pf.CreateDataParameter("@type", Type_name)
        params.DbType = DbType.String
        cmd.Parameters.Add(params)

        Try
            Dim dr As IDataReader = cmd.ExecuteReader


            Dim weekoffday As Integer
            Dim lemp_code As String

            Do While dr.Read()
                weekoffday = 6 - dr.Item("week_off_day")
                lemp_code = dr.Item("emp_unique_code")
                If weelyoff = 1 Then
                    Weekoffdates(lemp_code, weekoffday, weelyoff, 0)
                Else
                    Dim off_days As Integer = dr.Item("off_days")
                    Weekoffdates(lemp_code, weekoffday, weelyoff, off_days)
                End If
            Loop

        Catch ex As Exception
            MsgBox(ex.Message)

        End Try

    End Sub
    Private Sub Weekoffdates(ByVal lemp_code As String, ByVal weekoffday As Integer, ByVal weeklyoff As Decimal, ByVal off_days As Integer)
        Dim wfdt As Date = DateTimePicker1.Text
        Dim wtdt As Date = DateTimePicker2.Text
        Dim offdate As Date = wfdt.Date
        offdate = offdate.Date.AddDays(Weekday(offdate) + weekoffday - 1)
        If weeklyoff = 1 Then
            Do While offdate <= wtdt.Date
                updateweekoffday(offdate, lemp_code, weeklyoff)
                offdate = offdate.Date.AddDays(7)
            Loop
        ElseIf weeklyoff = 0.5 Then
            updatehalfoffdays(offdate, lemp_code, weeklyoff, off_days)
        End If


    End Sub
    Private Sub updateweekoffday(ByVal mydate As Date, ByVal emp_code As String, ByVal off_day As Decimal)
        Dim csql As String = ""
        '  csql = "delete from  Employee_week_offdays where emp_unique_code='" + emp_code + "' and week_off_day='" + mydate.ToString + "'" + Keys.Enter.ToString
        csql = csql + "insert into Employee_week_offdays (emp_unique_code,week_off_date,off_day) " + _
               "values('" + emp_code + "','" + mydate.ToString + "'," + off_day.ToString + ")"
        Dim pf As ProviderFactory = New ProviderFactory
        pf.Provider = SqlDataBase.ConnectionType
        Dim myconn As IDbConnection = pf.CreateConnection(dssToolKit.myfunc.Appvaribales.ConnectionString)
        Dim cmd As IDbCommand = pf.CreateCommand(csql, myconn)
        myconn.Open()
        Try
            cmd.ExecuteNonQuery()
        Catch ex As Exception
            MsgBox(ex.Message)
        End Try
        myconn.Close()
    End Sub