Primer - Ultimo dia del mes

Option Explicit On

Public Class form_dia_mes

    Function nombredia(ByVal dia As Integer)

        Select Case dia

            Case 1 : nombredia = "Domingo"

            Case 2 : nombredia = "Lunes"

            Case 3 : nombredia = "Martes"

            Case 4 : nombredia = "Miercoles"

            Case 5 : nombredia = "Jueves"

            Case 6 : nombredia = "Viernes"

            Case 7 : nombredia = "Sabado"

        End Select

    End Function

    Private Sub Btnmostrar_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnmostrar.Click

        Dim diaultimo, diaprimero As Integer

        Dim fecha As Date

        fecha = Microsoft.VisualBasic.DateValue(DateTimePicker1.Value)

        Dim Primer As Date

        Dim Ultimo As Date

        Primer = DateSerial(Year(fecha), Month(fecha) + 0, 1)

        Ultimo = DateSerial(Year(fecha), Month(fecha) + 1, 0)

        diaprimero = Microsoft.VisualBasic.Weekday(Primer)

        diaultimo = Microsoft.VisualBasic.Weekday(Ultimo)

        txtultimo.Text = nombredia(diaultimo)

        txtprimero.Text = nombredia(diaprimero)

        Dim dia As New Date

        dia = Microsoft.VisualBasic.DateValue(DateTimePicker1.Value).ToShortDateString

        dia = dia.AddDays(-dia.Day + 1)

        txtdiaprimero.Text = dia

        dia = dia.AddDays(-dia.Day + 1).AddMonths(1).AddDays(-1)

        txtdiaultimo.Text = dia

    End Sub

    Private Sub Button2_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button2.Click

        Dim salida As Integer = MsgBox("Desea Salir?",

        MsgBoxStyle.YesNo + 32, "Mensaje al usuario")

        If salida = 6 Then

            Me.Close()

        End If

    End Sub

End Class