如何在vb.net中每两周创建一次任务提醒

Question

我希望从数据库中已经输入的日期开始，每两周创建一次任务提醒(用户将其添加到数据库中的开始日期点)。根据一周中白天的情况，我试了一试，但没有结果，如果有人有什么想法，我会很感激的。

cmd5.CommandText = "select * from task where frequence='2W' "
    da5.SelectCommand = cmd1
    da5.Fill(ds5, "0")
    DataGridView6.Columns.Add("fr", "fr")
    DataGridView6.Columns.Add("class", "class")

    For i As Integer = 0 To ds5.Tables(0).Rows.Count - 1
        If Date.Now.DayOfWeek > 3 Then
            If CType(ds5.Tables(0).Rows(i).Item(3), Date).DayOfWeek = Date.Now.DayOfWeek Or CType(ds5.Tables(0).Rows(i).Item(3), Date).DayOfWeek - ???? = Date.Now.DayOfWeek Then
                DataGridView6.Rows.Add(ds5.Tables(0).Rows(i).Item(4), CType(ds5.Tables(0).Rows(i).Item(3), Date).DayOfWeek)
            End If
        End If
        If Date.Now.DayOfWeek < 4 And Date.Now.DayOfWeek <> 0 Then
            If CType(ds5.Tables(0).Rows(i).Item(3), Date).DayOfWeek = Date.Now.DayOfWeek Or CType(ds5.Tables(0).Rows(i).Item(3), Date).DayOfWeek + ???? = Date.Now.DayOfWeek Then
                DataGridView6.Rows.Add(ds5.Tables(0).Rows(i).Item(4), CType(ds5.Tables(0).Rows(i).Item(3), Date).DayOfWeek)
            End If
        End If
    Next

“？”我不知道怎样才能得到正确的结果！有人能帮帮我吗！

Answer 1

正如我从您的评论中了解到的，您只对区间分析部分感兴趣，即确定今天的日期是否在数据库中定义的给定条件之前/之后(使用start_date和frequency)。这里有一个示例代码来处理这个问题：

Dim start_date As Date = Now.AddDays(-14) 'start_date value to be taken from the DB
Dim frequency As TimeSpan = TimeSpan.FromDays(14) 'Number of days as a function of the given frequency in your DB; this is for 2W.
Dim elapsedDays As TimeSpan = Now.Subtract(start_date)

If (elapsedDays >= frequency) Then
    'NOTIFY USER -> it has passed, at least, "frequency" number of days from "start_date"
    If (elapsedDays > frequency) Then
        Dim addDays As Integer = elapsedDays.Subtract(frequency).Days
        Dim dateWhenTargetMet As Date = Now.AddDays(-addDays)
        'Tell user that the target was met "addDays" ago, on "dateWhenTargetMet" 
    End If
End If

上面的代码检查当前日期是否等于(或晚于) start_date + frequency天数。