.NET Custom Drag'n Drop Control

Code

Class DragDrop

    Inherits ContainerControl

    Private Shape As GraphicsPath

    Private Multiple As Boolean

    Private files As String()

    Private filter As String()

    Private msgMultiple As String

    Private msgExtension As String

    Public Event FileDropped As EventHandler



    Sub New()

      SetStyle(ControlStyles.SupportsTransparentBackColor, True)

      SetStyle(ControlStyles.UserPaint, True)

      BackColor = Color.Transparent

      Me.Size = New Size(187, 117)

      Me.AllowDrop = True

      Padding = New Padding(1, 1, 1, 1)

      DoubleBuffered = True

    End Sub

    Property AllowMultiple() As Boolean

      Get

      Return Multiple

      End Get



      Set(ByVal Value As Boolean)

      Multiple = Value

      End Set

    End Property

    Property ExtensionFilter() As String()

      Get

      Return filter

      End Get

      Set(ByVal Value As String())

      filter = Value

      End Set

    End Property

    Property MultipleError() As String

      Get

      Return msgMultiple

      End Get

      Set(ByVal Value As String)

      msgMultiple = Value

      End Set

    End Property

    Property ExtensionError() As String

      Get

      Return msgExtension

      End Get

      Set(ByVal Value As String)

      msgExtension = Value

      End Set

    End Property

    ReadOnly Property DroppedFiles As String()

      Get

      Return files

      End Get

    End Property

    Private Sub Me_DragDrop(sender As Object, e As DragEventArgs) Handles Me.DragDrop

      Dim extMatch As Boolean = False

      Dim tmpArray = e.Data.GetData(DataFormats.FileDrop)

      If tmpArray.Length > 1 And Multiple = False Then

      If msgMultiple.Length > 0 Then

            MsgBox(msgMultiple, MsgBoxStyle.Critical, "Error")

      End If

      Else

      If filter.Length > 0 Then

            Dim i As Integer

            For i = 0 To tmpArray.Length - 1

            For Each ext As String In filter

            If tmpArray(i).EndsWith(ext) Then

            extMatch = True

            End If

            Next

            Next

            If extMatch = True Then

            files = e.Data.GetData(DataFormats.FileDrop)

            RaiseEvent FileDropped(Me, e)



            Else

            If msgExtension.Length > 0 Then

            MsgBox(msgExtension, MsgBoxStyle.Critical, "Error")

            End If

            End If

      Else

            files = e.Data.GetData(DataFormats.FileDrop)

            RaiseEvent FileDropped(Me, e)

      End If

      End If

    End Sub



    Private Sub Me_DragEnter(sender As Object, e As DragEventArgs) Handles Me.DragEnter

      If e.Data.GetDataPresent(DataFormats.FileDrop) Then

      e.Effect = DragDropEffects.Copy

      End If

    End Sub

    Protected Overrides Sub OnResize(ByVal e As System.EventArgs)

      MyBase.OnResize(e)

      Shape = New GraphicsPath

      With Shape

      .AddArc(0, 0, 10, 10, 180, 90)

      .AddArc(Width - 11, 0, 10, 10, -90, 90)

      .AddArc(Width - 11, Height - 11, 10, 10, 0, 90)

      .AddArc(0, Height - 11, 10, 10, 90, 90)

      .CloseAllFigures()

      End With

    End Sub



    Protected Overrides Sub OnPaint(ByVal e As System.Windows.Forms.PaintEventArgs)

      MyBase.OnPaint(e)



      Dim p As New Pen(Color.FromArgb(180, 180, 180)) With {.DashStyle = DashStyle.Dash, .Width = 5}

      Dim B As New Bitmap(Width, Height)

      Dim G = Graphics.FromImage(B)

      G.SmoothingMode = SmoothingMode.HighQuality

      G.Clear(Color.Transparent)

      G.FillPath(Brushes.White, Shape)

      G.DrawPath(p, Shape)



      Dim F As New Font("Trebuchet MS", 20, FontStyle.Bold)

      Dim sf As New StringFormat With {.LineAlignment = StringAlignment.Center, .Alignment = StringAlignment.Center}

      G.DrawString(Me.Text, F, New SolidBrush(Color.FromArgb(221, 221, 221)), ClientRectangle, sf)



      G.Dispose()

      e.Graphics.DrawImage(B.Clone(), 0, 0)

      B.Dispose()

    End Sub

End Class

Code

DragDrop1.AllowMultiple=False 'This will disable multiple file dropping.



DragDrop1.MultipleError="Only 1 file can be drop." 'Leave blank for no messagebox.



DragDrop1.ExtensionFilter = {".exe", ".jpg", ".png"} 'Use string array with this format.Leave blank for no filter.



DragDrop1.ExtensionError = "This file type not allowed." 'Leave blank for no messagebox.



Dim files as string() = DragDrop1.DroppedFiles() 'This property will always return dropped files as string array whether allow multiple selected true or false.

'You can use DragDrop1.DroppedFiles(0) if you set AllowMultiple to false.