Netron是一个用于实现类似简单Visio图形化功能的C#开源项目，作者在2006年停止了2.5版的更新，随后在2007年发布了3.0版。网络上也出现了基于2.5版的轻量版，相对来说简单很多，虽然可以用来入门学习，但被阉割过的项目总显得有些无味。3.0版相对2.5版来说是质的飞跃，但的的确确确确实实实实在在太“重量”了，所以研究学习2.5版是最折中的选择。
我已经把原版的C#源码转换成VB.net，这样对VBFans来说也许是件令人鼓舞的事情。除了语言上的转换之外，还对项目中原有的bug和不足做了如下的小范围修改。
(魏滔序原创，转帖请注明出处。)
DiagramControl：删除选中的项目
添加方法：
Public Sub RemoveSelectedItems()
For i As Int32 = SelectedItems.Count - 1 To 0 Step -1
Controller.Model.Remove(SelectedItems(i))
Next
Me.Invalidate()
End Sub
Selecttion：执行DiagramControl.SelectedItems.Clear时反选
PRivate Shared Sub RaiseonNewSelection()
RemoveHandler mSelection.OnClear, AddressOf OnShowTracker
RemoveHandler mSelection.OnItemRemoved, AddressOf OnShowTracker
AddHandler mSelection.OnClear, AddressOf OnShowTracker
AddHandler mSelection.OnItemRemoved, AddressOf OnShowTracker
RaiseEvent OnNewSelection(Nothing, EventArgs.Empty)
End Sub
Private Shared Sub OnShowTracker(ByVal sender As Object, ByVal e As EventArgs)
Controller.View.ShowTracker()
End Sub
CollectionBase：从索引移除项目时触发OnItemRemoved事件
Public Sub RemoveAt(ByVal index As Integer)
Dim Item As T = Me.innerList(index)
Me.innerList.RemoveAt(index)
RaiseonItemRemoved(Item)
End Sub
Connection：禁止连线缩放(去除缩放点和选中矩形框)
Public Sub New(ByVal mFrom As Point, ByVal mTo As Point, ByVal model As IModel)
MyBase.New(model)
MyBase.Resizable = False
Me.From = New Connector(mFrom, model)
Me.From.Name = "From"
Me.From.Parent = Me
Me.To = New Connector(mTo, model)
Me.To.Name = "To"
Me.To.Parent = Me
End Sub
View：Resizable = False 时去除获得焦点的选中矩形框
Public Shared Function GetTracker(ByVal rectangle As Rectangle, ByVal type As TrackerTypes, ByVal showHandles As Boolean) As ITracker
Select Case type
Case TrackerTypes.Default
If defTracker Is Nothing Then
defTracker = New DefaultTracker()
End If
If showHandles Then
defTracker.Transform(rectangle)
Else
defTracker.Transform(Nothing)
End If
defTracker.ShowHandles = showHandles
Return defTracker
Case Else
Return Nothing
End Select
End Function
TransformTool：实现鼠标移动时自动变换指针图标
在 Public Sub MouseMove(ByVal e As MouseEventArgs) Implements IMouseListener.MouseMove 的过程中添加：
If e.Button = MouseButtons.None AndAlso Enabled AndAlso (Not IsSuspended) Then
If Selection.SelectedItems.Count > 0 Then
Dim gripPoint As Point = Me.Controller.View.Tracker.Hit(e.Location)
Dim c As Cursor = Nothing
Select Case gripPoint.X
Case -1
Select Case gripPoint.Y
Case -1
c = Cursors.SizeNWSE
Case 0
c = Cursors.SizeWE
Case 1
c = Cursors.SizeNESW
End Select
Case 0
Select Case gripPoint.Y
Case -1
c = Cursors.SizeNS
Case 1
c = Cursors.SizeNS
End Select
Case 1
Select Case gripPoint.Y
Case -1
c = Cursors.SizeNESW
Case 0
c = Cursors.SizeWE
Case 1
c = Cursors.SizeNWSE
End Select
End Select
Controller.View.CurrentCursor = c
End If
End If
TransformTool：缩放图形完成时刷新视图
Public Sub MouseUp(ByVal e As MouseEventArgs) Implements IMouseListener.MouseUp
If IsActive Then
DeactivateTool()
Dim cmd As New TransformCommand(Me.Controller, origin, scalex, scaley, transformers)
Me.Controller.UndoManager.AddUndoCommand(cmd)
Me.Controller.View.Invalidate()
End If
End Sub
ShapeBase：限制图形的最小高度和宽度为10像素
Public Overridable Sub Transform(ByVal x As Integer, ByVal y As Integer, ByVal width As Integer, ByVal height As Integer) Implements IShape.Transform
Dim a, b As Double
Dim p As Point
If width <= 10 Or height <= 10 Then Exit Sub
For Each cn As IConnector In Me.mConnectors
a = Math.Round((CDbl(cn.Point.X) - CDbl(mRectangle.X)) / CDbl(mRectangle.Width), 1) * width + x - cn.Point.X
b = Math.Round((CDbl(cn.Point.Y) - CDbl(mRectangle.Y)) / CDbl(mRectangle.Height), 1) * height + y - cn.Point.Y
p = New Point(Convert.ToInt32(a), Convert.ToInt32(b))
cn.Move(p)
Next cn
mRectangle = New Rectangle(x, y, width, height)
End Sub