Как обновить datetimepicker с помощью sendmessage

---

Я пытаюсь написать программу, которая будет отправлять информацию сторонней программе с помощью SendMessage. До сих пор мне удавалось работать с полями со списком и текстовыми полями, но когда дело доходит до обновления элемента управления DateTimePicker, я натыкаюсь на кирпичную стену.

При использовании SendMessage в DateTimePicker он, по-видимому, вообще не изменяет дату/данные. Кто-нибудь еще сталкивался с этой проблемой?

Я действительно хочу, чтобы вы знали, что я работаю над этим уже несколько дней и гуглил все, что знаю, но так и не нашел решения. В общем, я звоню:

Что я уже пробовал:

Declare Function SendMessage Lib "user32.dll" Alias "SendMessageA" (ByRef hwnd As Int32, ByRef wMsg As Int32, ByRef wParam As Int32, ByRef lParam As SYSTEMTIME) As Int32

    <StructLayout(LayoutKind.Sequential)> Structure SYSTEMTIME
        Public wYear As Int16
        Public wMonth As Int16
        Public wDayOfWeek As Int16
        Public wDay As Int16
        Public wHour As Int16
        Public wMinute As Int16
        Public wSecond As Int16
        Public wMilliseconds As Int16
    End Structure

    Public Const DTM_FIRST As Int32 = &H1000
    Public Const DTM_GETSYSTEMTIME As Int32 = (DTM_FIRST + 1)
    Public Const DTM_SETSYSTEMTIME As Int32 = (DTM_FIRST + 2)

    Public Shared Sub SendMessageDateToControl(ControlHandle As Integer, Message As Date)

        Dim hwnd, datehwnd As Integer
        Dim gettime As New SYSTEMTIME
        Dim changetime As New SYSTEMTIME
        changetime.wDay = Message.Day
        changetime.wMonth = Message.Month
        changetime.wYear = Message.Year
        SendMessage(ControlHandle, DTM_GETSYSTEMTIME, 0, gettime)
        SendMessage(ControlHandle, DTM_SETSYSTEMTIME, 0, changetime)

    End Sub

    Public Shared Function GetChildWindows(ByVal ParentHandle As IntPtr) As IntPtr()
        Dim ChildrenList As New List(Of IntPtr)
        Dim ListHandle As GCHandle = GCHandle.Alloc(ChildrenList)
        Try
            EnumChildWindows(ParentHandle, AddressOf EnumWindow, GCHandle.ToIntPtr(ListHandle))
        Finally
            If ListHandle.IsAllocated Then ListHandle.Free()
        End Try
        Return ChildrenList.ToArray
    End Function

    Public Shared Function GetWindowHandle(WindowCaption As String) As Integer
        Return FindWindow(Nothing, WindowCaption)
    End Function

    Private Sub GetControlInfo()

        ' Get a Window's Handle
        Dim hWnd = WindowControlHandleInfo.GetWindowHandle(TextBoxWindowName.Text)


        If (hWnd = 0) Then
            MessageBox.Show("Control Window Was Not Found", Application.ProductName, MessageBoxButtons.OK, MessageBoxIcon.Information)
            Return
        End If

        ' Get all the Control Handles for the Forms Child
        Dim rtnChildWindows As IntPtr() = WindowControlHandleInfo.GetChildWindows(hWnd)

        If rtnChildWindows.Length = 0 Then Return ' No Controls were Found

        myControlInfo = New List(Of WindowControlInfo)
        Dim zOrder As Integer = 0

        ' Loop Through Each Child Window and add it to the myControlInfo
        For Each i As Integer In rtnChildWindows

            ' Get the Class Name
            Dim strClassName As String = CStr(WindowControlHandleInfo.GetClassName(i))
            ' Get the Controls Caption
            Dim ControlText As String = WindowControlHandleInfo.GetMesasgeFromControl(i)

            myControlInfo.Add(New WindowControlInfo(strClassName, zOrder, i, ControlText))
            zOrder += 1

        Next

    End Sub

    Private Sub ButtonSendDateToDateTimePicker_Click(sender As Object, e As EventArgs) Handles ButtonSendDateToDateTimePicker.Click
        WindowControlHandleInfo.SendMessageDateToControl(TextBoxHandelDateTimePicker.Text, "02/01/1991")
    End Sub

Я тоже пробовал:

    Public Declare Function SendMessage Lib "user32.dll" Alias "SendMessageA" (ByVal hwnd As Int32, ByVal wMsg As Int32, ByVal wParam As Int32, ByVal lParam As String) As Int32
Public Const WM_SETTEXT As Int32 = &HC
Public Const WM_GETTEXT As Int32 = &HD
SendMessage(chwnd, WM_SETTEXT, 0, "02/01/1991")

Ни один из них не изменяет значение DateTimePicker.

---