HOW TO：从资源管理器中拖放文件到控件

当然，这里所谓的文件是指完整的文件名称，至于文件的内容，须按实际情况进一步的操作。

我这里的控件为一个ListBox。代码如下：

Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load

   Me.ListBox1.AllowDrop = True

End Sub

Private Sub ListBox1_DragEnter(ByVal sender As Object, ByVal e As System.Windows.Forms.DragEventArgs) Handles ListBox1.DragEnter

   Dim o As Object = e.Data.GetData(DataFormats.FileDrop)

   If Not o Is Nothing Then

      e.Effect = DragDropEffects.Copy

   End If

End Sub

Private Sub ListBox1_DragDrop(ByVal sender As Object, ByVal e As System.Windows.Forms.DragEventArgs) Handles ListBox1.DragDrop

   Dim FileNames As String() = CType(e.Data.GetData(DataFormats.FileDrop), String())

   Me.ListBox1.Items.AddRange(FileNames)

End Sub


重写这个HOW TO，主要的是看到有人用API实现，代码如下：

Private Const WM_DROPFILES As Integer = 563

Private Declare Function DragAcceptFiles Lib "shell32.dll" (ByVal hwnd As IntPtr, ByVal accept As Boolean) As Long

Private Declare Function DragQueryFile Lib "shell32.dll" (ByVal hDrop As IntPtr, ByVal file As Integer, ByVal fileName As System.Text.StringBuilder, ByVal size As Int32) As Int32

Private Declare Sub DragFinish Lib "Shell32.dll" (ByVal hDrop As IntPtr)

Protected Overrides Sub WndProc(ByRef m As System.Windows.Forms.Message)

  If m.Msg = WM_DROPFILES Then

    Dim iNumOfFiles As Int32 = DragQueryFile(m.WParam, &HFFFFFFFF, Nothing, 0)

    Dim iPnt As Int32

    For iPnt = 0 To iNumOfFiles - 1

      Dim sb As New System.Text.StringBuilder(256)

      Dim iRet As Int32 = DragQueryFile(m.WParam, iPnt, sb, sb.Capacity)

      ListBox1.Items.Add(sb.ToString)

   Next

   DragFinish(m.WParam)

Else

   MyBase.WndProc(m)

End If

End Sub


Private Sub Form1_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles MyBase.Load

   DragAcceptFiles(ListBox1.Handle, True)

End Sub