檢索ComboBox通過使用SendMessage API計數和項目

Question

我想獲得一個計數和列表ComboBox控制這不是我的，所以我不能修改代碼。

例如，通過使用SendMessage API可以控制目標應用程序。

但是，如何通過掛鉤檢索目標控件的整個列表？

Answer 1

你可以找到ComboBox控制消息在這裏的列表：

• MSDN - ComboBox Control Messages
• PInvoke - CB_ Constants

要獲得項目數，您需要使用CB_GETCOUNT消息，並獲得一個項目的文本你可以使用CB_GETLBTEXT消息。

例

在這裏，我創建了一個ComboBoxHelper類，你可以通過傳遞ComboBox的Handle創建它的實例，並使用其屬性：

• SelectedIndex爲Integer：選擇指數返回，返回 - 1如果沒有選擇項目。
• Selectedtext作爲String：返回所選項目的文本，如果未選擇項目，則返回String.Empty。
• ItemsCount as Integer：返回項目數。
• Items(index)爲String：返回文本中指定的項目（在指定索引的項目）
• Items爲List(of String)的：返回組合框的項目列表。如果沒有項目，它將返回一個空列表。

Public Class ComboBoxHelper 
    Private hWnd As IntPtr 
    Const CB_GETCURSEL As Integer = &H147 
    Const CB_SETCURSEL As Integer = &H14E 
    Const CB_GETCOUNT As Integer = &H146 
    Const CB_GETLBTEXT As Integer = &H148 
    Const CB_GETLBTEXTLEN As Integer = &H149 
    <System.Runtime.InteropServices.DllImport("user32.dll")> _ 
    Shared Function SendMessage(ByVal hWnd As IntPtr, ByVal Msg As Integer, _ 
     ByVal wParam As Integer, ByRef lParam As Integer) As IntPtr 
    End Function 
    <System.Runtime.InteropServices.DllImport("user32.dll")> _ 
    Shared Function SendMessage(ByVal hWnd As IntPtr, ByVal Msg As Integer, _ 
     ByVal wParam As Integer, ByVal lParam As System.Text.StringBuilder) As IntPtr 
    End Function 
    Public Sub New(handle As IntPtr) 
     hWnd = handle 
    End Sub 
    Public Property SelectedIndex As Integer 
     Get 
      Return SendMessage(hWnd, CB_GETCURSEL, 0, 0).ToInt32() 
     End Get 
     Set(ByVal value As Integer) 
      SendMessage(hWnd, CB_SETCURSEL, value, 0).ToInt32() 
     End Set 
    End Property 
    Public ReadOnly Property ItemsCount As Integer 
     Get 
      Return SendMessage(hWnd, CB_GETCOUNT, 0, 0).ToInt32() 
     End Get 
    End Property 
    Public ReadOnly Property SelectedText As String 
     Get 
      Dim index = Me.SelectedIndex 
      If (Me.SelectedIndex = -1) Then 
       Return String.Empty 
      End If 
      Return Me.Items(index) 
     End Get 
    End Property 
    Public ReadOnly Property Items() As List(Of String) 
     Get 
      If (ItemsCount > 0) Then 
       Return Enumerable.Range(0, ItemsCount) _ 
           .Select(Function(index) Items(index)).ToList() 
      Else 
       Return New List(Of String) 
      End If 
     End Get 
    End Property 
    Public ReadOnly Property Items(index As Integer) As String 
     Get 
      If (index < 0 OrElse index >= ItemsCount) Then 
       Throw New ArgumentOutOfRangeException("index") 
      End If 
      Dim length = SendMessage(hWnd, CB_GETLBTEXTLEN, index, 0).ToInt32() 
      Dim text As New System.Text.StringBuilder(length) 
      SendMessage(hWnd, CB_GETLBTEXT, index, text) 
      Return text.ToString() 
     End Get 
    End Property 
End Class 

下面是類的使用的一個示例：

Dim combo As New ComboBoxHelper(hWnd) 'You have hWnd 
MessageBox.Show(combo.ItemsCount.ToString()) 
MessageBox.Show(combo.SelectedIndex.ToString()) 
MessageBox.Show(combo.SelectedText.ToString()) 
combo.Items.ForEach(Function(item) MessageBox.Show(item))