populate TextBoxes base on date value selected in DatePicker

Hi,@zleug. Welcome to Microsoft Q&A. 

You could refer to the following code to achieve the function you want.

MainWindow.xaml

<Grid>

    <Grid.RowDefinitions>

        <RowDefinition/>

        <RowDefinition/>

    </Grid.RowDefinitions>

    <DatePicker x:Name="MyDatePicker" SelectedDateChanged="MyDatePicker_SelectedDateChanged"></DatePicker>

    <StackPanel Orientation="Horizontal" Grid.Row="1">

    <TextBox x:Name="txbWeek"   Margin="10" Width="100" Height="50"></TextBox>

        <TextBox x:Name="txbMonDate"  Margin="10" Width="100" Height="50"></TextBox>

        <TextBox x:Name="txbFriDate"  Margin="10" Width="100" Height="50"></TextBox>

    </StackPanel>

</Grid>

MainWindow.xaml.vb

Class MainWindow

    Private Sub MyDatePicker_SelectedDateChanged(sender As Object, e As SelectionChangedEventArgs)

        Dim value As String = MyDatePicker.Text

 

        If Not String.IsNullOrEmpty(value.ToString()) Then

            'The time value obtained by DatePicker Is converted from string type to DateTime

            Dim mydate = value.ToString().Split("/")

            Dim dateValue As New DateTime(mydate(2), mydate(0), mydate(1))

            'Get Week

            txbWeek.Text = GetWeekOfMonth(dateValue)

 

            'Get the week number Of the current day

            Dim Week = dateValue.DayOfWeek

            'Sunday 's enumeration is 0, set it to 7 to facilitate subsequent calculation of time difference

            If Week = 0 Then

                Week = 7

            End If

            'Get Monday

            Dim addDate = DayOfWeek.Monday - Week

            txbMonDate.Text = dateValue.AddDays(addDate)

            'Get Friday

            addDate = DayOfWeek.Friday - Week

            txbFriDate.Text = dateValue.AddDays(addDate)

        Else

            txbWeek.Text = ""

            txbMonDate.Text = ""

            txbFriDate.Text = ""

        End If

    End Sub

 

 

    Function GetWeekOfMonth(dateValue As DateTime) As Integer

        ' Get the first day of the month

        Dim firstDayOfMonth As New DateTime(dateValue.Year, dateValue.Month, 1)

 

        'Get the week number for this date and the first day of the month

        Dim firstWeekOfYear As Integer = DatePart(DateInterval.WeekOfYear, firstDayOfMonth, FirstDayOfWeek.System)

        Dim currentWeekOfYear As Integer = DatePart(DateInterval.WeekOfYear, dateValue, FirstDayOfWeek.System)

 

        ' Calculate the week number of the month that the date falls in

        Return currentWeekOfYear - firstWeekOfYear + 1

    End Function

End Class

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