基于VB语言的TransCAD二次开发代码

以下是一个基于VB语言的TransCAD二次开发代码示例，用于在TransCAD中创建一个新文件并绘制一个简单的道路网络。

Sub Main()

    ' Create a new TransCAD application instance
    Dim app As TransCAD.Application
    Set app = New TransCAD.Application
    
    ' Make the TransCAD application visible
    app.Visible = True
    
    ' Create a new document
    Dim doc As TransCAD.Document
    Set doc = app.Documents.Add
    
    ' Get the network object from the document
    Dim network As TransCAD.ITransportationNetwork
    Set network = doc.TransportationNetwork
    
    ' Create a new graph
    Dim graph As TransCAD.ITransportationGraph
    Set graph = network.CreateGraph("MyGraph")
    
    ' Add nodes to the graph
    Dim node1 As TransCAD.ITransportationNode
    Set node1 = graph.CreateNode(0, 0)
    Dim node2 As TransCAD.ITransportationNode
    Set node2 = graph.CreateNode(1, 0)
    Dim node3 As TransCAD.ITransportationNode
    Set node3 = graph.CreateNode(1, 1)
    Dim node4 As TransCAD.ITransportationNode
    Set node4 = graph.CreateNode(0, 1)
    
    ' Add edges to the graph
    Dim edge1 As TransCAD.ITransportationEdge
    Set edge1 = graph.CreateEdge(node1, node2)
    Dim edge2 As TransCAD.ITransportationEdge
    Set edge2 = graph.CreateEdge(node2, node3)
    Dim edge3 As TransCAD.ITransportationEdge
    Set edge3 = graph.CreateEdge(node3, node4)
    Dim edge4 As TransCAD.ITransportationEdge
    Set edge4 = graph.CreateEdge(node4, node1)
    
    ' Refresh the view
    doc.Views.Item(0).Refresh
    
    ' Clean up
    Set edge4 = Nothing
    Set edge3 = Nothing
    Set edge2 = Nothing
    Set edge1 = Nothing
    Set node4 = Nothing
    Set node3 = Nothing
    Set node2 = Nothing
    Set node1 = Nothing
    Set graph = Nothing
    Set network = Nothing
    Set doc = Nothing
    Set app = Nothing

End Sub

这段代码使用VB语言编写，利用TransCAD API创建一个新的TransCAD文件，并在其中绘制一个简单的道路网络。代码中创建了四个节点和四条边，然后刷新了视图以显示道路网络。最后，清理了所有对象的引用。