功能：点击datagrid并且按住键盘上的ctrl或shift可选择多行

Public Class MyDataGridCLASS
Inherits DataGrid
Private m As New ArrayList

Public ReadOnly Property MultiSelectedIndex() As Integer()
Get
Return m.ToArray(GetType(Integer))
End Get
End Property

Protected Overrides Sub OnMouseDown(ByVal e As System.Windows.Forms.MouseEventArgs)
Debug.WriteLine("DataGrid has hit")
Dim posdg As Point = New Point(e.X, e.Y)
Dim hitDG As DataGrid.HitTestInfo = HitTest(posdg)
If HitDataGrid(hitDG) Then
MyBase.OnMouseDown(e)
Debug.WriteLine("Mousedown has gogogo.....")
End If
End Sub

Private Function HitDataGrid(ByVal Hit As DataGrid.HitTestInfo) As Boolean
Try
Select Case Me.ModifierKeys
Case Keys.Control
If Hit.Row > -1 Then
If m.IndexOf(Hit.Row) > -1 Then
m.Remove(Hit.Row)
Me.UnSelect(Hit.Row)
Else
m.Add(Hit.Row)
Me.Select(Hit.Row)
End If
End If
Return False
Case Keys.Shift
If Hit.Row > -1 Then
For Each IndexOld As Integer In m
Me.UnSelect(IndexOld)
Next
m.Clear()
Dim i, intStep As Integer
If Hit.Row > Me.CurrentRowIndex Then
intStep = 1
Else
intStep = -1
End If
For i = Me.CurrentRowIndex To Hit.Row Step intStep
m.Add(i)
Me.Select(i)
Next
End If
Return False
Case Else
For Each index As Integer In m
Me.UnSelect(index)
Next
m.Clear()
If Hit.Type = DataGrid.HitTestType.RowHeader Then
m.Add(Hit.Row)
End If
Return True
End Select
Catch ex As Exception
Debug.WriteLine(ex.ToString)
End Try
End Function
End Class