【解決方法】インデックスが範囲外でした。 負ではなく、コレクションのサイズより小さくなければなりません。 パラメータ名: インデックス VB.NET

 Sub read()
        Dim constring As String = "dsn=mysql_tabel;database=db1;server=localhost;iud=root"
        Dim con As New OdbcConnection(constring)
        'Dim con As New OdbcCommand(SQL)
        'dataload()
        con.Open()
        Dim query As String = "Select *From tbdata_reservasi"
        Dim cmd As New OdbcCommand(query, con)
        Dim dr As OdbcDataReader = cmd.ExecuteReader()

        While dr.Read
            Dim RoomNum_R As Integer = dr.GetInt32(7)
            Dim startdate As DateTime = dr.GetDate(9)
            Dim enddate As DateTime = dr.GetDate(10)

            Dim startdate_c As Integer = startdate.Day
            Dim enddate_c As Integer = enddate.Day
            Dim room1 As Integer = RoomNum_R - 1 
            Dim totaldays As Integer = enddate_c - startdate_c

            DG1(startdate_c, room1).Style.BackColor = Color.Red

            For i = 1 To totaldays
                DG1(startdate_c + i, room1).Style.BackColor = Color.Red

                totaldays -= 1
                'totaldays = -1

            Next

        End While
    End Sub

What I have tried:

i dont know for solution,if the number of RoomNum only 1 digit there is no error,but if mor digit at the RoomNum it will be error "<pre>Index was out of range. Must be non-negative and less than the size of the collection. Parameter name: index"