Question

Image 1
当我尝试添加新帐单时会出现问题。

消息说：

从字符串转换＆＃34; 4/20 / 2017＆＃34;键入＆＃39; date＆＃39;无效。在Microsoft.VisualBasic.CompilerServices.conversions.ToDate（字符串值）

第1054行中的问题Dim duedate为String = DateAdd("d", +10, CDate(GetLastDayOfMonth))和第1102行<pre>set_CutoffDates

    Private Sub set_CutoffDates()
        sqlstring = "SELECT " &
            "       * " &
            "   FROM " &
            "       tblBillingProcess "

        read_record(sqlstring, "tblBillingProcess")
        txtDate.Text = Date.Now.ToShortDateString

        ' check if first billing get the last month's dates
        If ds.Tables("tblBillingProcess").Rows.Count = 0 Then

            'Dim datenow As Date = Now.Date
            'Dim Prev_Month As String = Month(DateAdd("m", -1, datenow))
            'Dim Prev_Year As String = Year(DateAdd("m", -1, datenow))
            'Dim firstdayprevmonth As String = Prev_Month & "/01/" & Prev_Year
            'Dim GetLastDayOfMonth As String = DateSerial(CInt(Prev_Year), CInt(Prev_Month) + 1, 0)
            'txtFrom.Text = firstdayprevmonth
            'txtTo.Text = GetLastDayOfMonth

            Dim datenow As Date = Now.Date
            Dim Prev_Month As String = Month(DateAdd("m", -1, datenow))
            Dim Prev_Year As String = Year(DateAdd("m", -1, datenow))
            'Dim firstdayprevmonth As String = Prev_Month & "/01/" & Prev_Year
            Dim periodFrom As String = Prev_Month & "/21/" & Prev_Year
            Dim NOW_Month As String = Month(datenow)
            Dim NOW_Year As String = Year(datenow)
            Dim firstdayofmonth As String = NOW_Month & "/01/" & NOW_Year
            Dim GetLastDayOfMonth As String = NOW_Month & "/20/" & NOW_Year
            'Dim duedate As String = DateAdd("d", +10, datenow)
            Dim duedate As String = DateAdd("d", +10, GetLastDayOfMonth)

            txtFrom.Text = periodFrom
            txtTo.Text = GetLastDayOfMonth
            txtDueDate.Text = duedate
        Else
            Dim datenow As Date
            'sqlstring = "SELECT " & _
            '    "       MAX(Periodfrom) as Periodfrom " & _
            '    "   FROM " & _
            '    "       tblBillingProcess "
            sqlstring = "SELECT " &
           "       MAX(Periodto) as Periodfrom " &
           "   FROM " &
           "       tblBillingProcess "

            read_record(sqlstring, "tblBillingProcessdate")
            datenow = CDate(ds.Tables("tblBillingProcessdate").Rows(0).Item("Periodfrom").ToString)
            'Dim Prev_Month As String = Month(DateAdd("m", -1, datenow))
            'Dim Prev_Year As String = Year(DateAdd("m", -1, datenow))
            Dim Prev_Month As String = Month(datenow)
            Dim Prev_Year As String = Year(datenow)
            Dim periodFrom As String = Prev_Month & "/21/" & Prev_Year
            Dim NOW_Month As String = Month(DateAdd("m", +1, datenow))
            Dim NOW_Year As String = Year(DateAdd("m", -1, datenow))
            Dim firstdayofmonth As String = NOW_Month & "/01/" & NOW_Year
            Dim GetLastDayOfMonth As String = NOW_Month & "/20/" & NOW_Year
            Dim duedate As String = DateAdd("d", +10, CDate(GetLastDayOfMonth))
            txtFrom.Text = periodFrom
            txtTo.Text = GetLastDayOfMonth
            txtDueDate.Text = duedate
        End If
    End Sub

Private Sub btnadd_Click(sender As Object, e As EventArgs) Handles btnadd.Click
        Try
            If btnadd.Text = "&Add" Then
                If Get_PendingPresentReading() = True Then
                    MsgBox("You must complete all present reading before creating new billing process ",
                                    MsgBoxStyle.Exclamation, Text)
                    Exit Sub
                End If
                reset_controls()
                dgProcess.Rows.Clear()
                txtBillingNo.Text = String.Empty
                txtFrom.Text = String.Empty
                txtTo.Text = String.Empty
                txtDueDate.Text = String.Empty
                txtDate.Text = String.Empty
                generate_billingNO()
                load_data()
                set_CutoffDates()
                btnadd.Text = "&Save"
                btnedit.Enabled = False
                btncancel.Enabled = True
                btnMain.Enabled = False
                btnFind.Enabled = False
            Else
                If MsgBox("Are you sure to save this transaction ",
                          MsgBoxStyle.Question + MsgBoxStyle.YesNo, Me.Text) = MsgBoxResult.No Then
                    Exit Sub
                End If

Answer 1

本月的最后一天，这是计算：

DateTime now = DateTime.Today;
var lastDate = new DateTime(now.Year, now.Month, DateTime.DaysInMonth(now.Year, now.Month);

然后显示它。它将使用您的默认文化。

txtDueDate.Text = lastDate.ToShortDateString();

如果你想要MM / dd / yyyy而不管它是否是一台en-US计算机，请使用：

txtDueDate.Text = lastDate.ToString("MM/dd/yyyy");

我无法找到错误VB

1 个答案: