using ESRI.ARCGIS.NetworkAnalysis;
public class ClsPathFinder
{
   private IGeometricNetwork m_ipGeometricNetwork;
   private IMap m_ipMap;
   private IPointCollection m_ipPoints;
   private IPointToEID m_ipPointToEID;
   private double m_dblPathCost =0;
   private IEnumNetEID m_ipEnumNetEID_Junctions;
   private IEnumNetEID m_ipEnumNetEID_Edges;
   private IPolyline    m_ipPolyline;

   #region Public Function
   //返回和设置当前地图
   public IMap SetOrGetMap
   {
    set{ m_ipMap = value;}
    get{return    m_ipMap;}
   }
   //打开网络
   public void OpenFeatureDatasetNetwork(IFeatureDataset FeatureDataset)
   {
    CloseWorkspace();   
    if (!InitializeNetworkAndMap(FeatureDataset))
     Console.WriteLine( "打开出错");
   }
   //输入点的集合
   public IPointCollection StopPoints
   {
    set{m_ipPoints= value;}
    get{return    m_ipPoints;}
   }
   
   //路径成本
   public double PathCost
   {
    get {return m_dblPathCost;}
   }
  
   //返回路径
   public IPolyline PathPolyLine()
   {
    IEIDInfo ipEIDInfo;
    IGeometry ipGeometry;   
    if(m_ipPolyline!=null)return m_ipPolyline;
   
    m_ipPolyline = new PolylineClass();
    IGeometryCollection ipNewGeometryColl = m_ipPolyline as IGeometryCollection;
   
    ISpatialReference ipSpatialReference = m_ipMap.SpatialReference;
    IEIDHelper ipEIDHelper = new EIDHelperClass();
    ipEIDHelper.GeometricNetwork = m_ipGeometricNetwork;  
    ipEIDHelper.OutputSpatialReference = ipSpatialReference;
    ipEIDHelper.ReturnGeometries = true;

    IEnumEIDInfo ipEnumEIDInfo = ipEIDHelper.CreateEnumEIDInfo(m_ipEnumNetEID_Edges);
    int count = ipEnumEIDInfo.Count;
    ipEnumEIDInfo.Reset();
    for(int i =0;i<count;i++)
    {
     ipEIDInfo = ipEnumEIDInfo.Next();
     ipGeometry = ipEIDInfo.Geometry;
     ipNewGeometryColl.AddGeometryCollection( ipGeometry as IGeometryCollection);
    }
    return m_ipPolyline;
   }
  
   //解决路径
   public void SolvePath(string WeightName)
   {
    try
    {   
     int intEdgeUserClassID;
     int intEdgeUserID;
     int intEdgeUserSubID;
     int intEdgeID;
     IPoint ipFoundEdgePoint;
     double dblEdgePercent;     
     /*C#中使用
      *ITraceFlowSolverGEN替代ITraceFlowSolver
      */
     ITraceFlowSolverGEN   ipTraceFlowSolver = new TraceFlowSolverClass() as ITraceFlowSolverGEN;
     INetSolver ipNetSolver = ipTraceFlowSolver as INetSolver;
     INetwork ipNetwork = m_ipGeometricNetwork.Network;
     ipNetSolver.SourceNetwork = ipNetwork;
     INetElements ipNetElements = ipNetwork as INetElements;
     int intCount = m_ipPoints.PointCount;
     //定义一个边线旗数组
     IEdgeFlag[] pEdgeFlagList = new EdgeFlagClass[intCount];
     for(int i = 0;i<intCount ;i++)
     {
      
      INetFlag ipNetFlag = new EdgeFlagClass()as INetFlag;
      IPoint   ipEdgePoint = m_ipPoints.get_Point(i);
      //查找输入点的最近的边线
      m_ipPointToEID.GetNearestEdge(ipEdgePoint, out intEdgeID,out ipFoundEdgePoint, out dblEdgePercent);
      ipNetElements.QueryIDs( intEdgeID, esriElementType.esriETEdge, out intEdgeUserClassID, out intEdgeUserID,out intEdgeUserSubID);
      ipNetFlag.UserClassID = intEdgeUserClassID;
      ipNetFlag.UserID = intEdgeUserID;
      ipNetFlag.UserSubID = intEdgeUserSubID;
      IEdgeFlag pTemp = (IEdgeFlag)(ipNetFlag as IEdgeFlag);
      pEdgeFlagList=pTemp;   
     }
     ipTraceFlowSolver.PutEdgeOrigins(ref pEdgeFlagList);
     INetSchema ipNetSchema = ipNetwork as INetSchema;
     INetWeight ipNetWeight = ipNetSchema.get_WeightByName(WeightName);

     INetSolverWeights ipNetSolverWeights = ipTraceFlowSolver as INetSolverWeights;
     ipNetSolverWeights.FromToEdgeWeight = ipNetWeight;//开始边线的权重
     ipNetSolverWeights.ToFromEdgeWeight = ipNetWeight;//终止边线的权重
     object [] vaRes =new object[intCount-1];
     //通过findpath得到边线和交汇点的集合
     ipTraceFlowSolver.FindPath(esriFlowMethod.esriFMConnected,
      esriShortestPathObjFn.esriSPObjFnMinSum,
      out m_ipEnumNetEID_Junctions,out m_ipEnumNetEID_Edges, intCount-1, ref vaRes);
     //计算成本
     m_dblPathCost = 0;
     for (int i =0;i<vaRes.Length;i++)
     {
      double m_Va =(double) vaRes;
      m_dblPathCost = m_dblPathCost + m_Va;
     }     
     m_ipPolyline = null;
    }
    catch(Exception ex)
    {
     Console.WriteLine(ex.Message);
    }
   }
   #endregion

   #region Private Function
   //初始化
   private bool InitializeNetworkAndMap(IFeatureDataset FeatureDataset)
   {
    IFeatureClassContainer ipFeatureClassContainer;
    IFeatureClass ipFeatureClass ;
    IGeoDataset ipGeoDataset;
    ILayer ipLayer ;
    IFeatureLayer ipFeatureLayer;
    IEnvelope ipEnvelope, ipMaxEnvelope ;
    double dblSearchTol;

    INetworkCollection ipNetworkCollection = FeatureDataset as INetworkCollection;
    int count = ipNetworkCollection.GeometricNetworkCount;
    //获取几何网络工作空间
    m_ipGeometricNetwork = ipNetworkCollection.get_GeometricNetwork(0);
    INetwork ipNetwork = m_ipGeometricNetwork.Network;

    if(m_ipMap!=null)
    {
     m_ipMap = new MapClass();
     ipFeatureClassContainer = m_ipGeometricNetwork as IFeatureClassContainer;
     count = ipFeatureClassContainer.ClassCount;
     for(int i =0;i<count;i++)
     {
      ipFeatureClass = ipFeatureClassContainer.get_Class(i);      
      ipFeatureLayer = new FeatureLayerClass();
      ipFeatureLayer.FeatureClass = ipFeatureClass;     
      m_ipMap.AddLayer( ipFeatureLayer);
     }
    }
    count = m_ipMap.LayerCount;
    ipMaxEnvelope = new EnvelopeClass();
    for(int i =0;i<count;i++)
    {
     ipLayer = m_ipMap.get_Layer(i);
     ipFeatureLayer = ipLayer as IFeatureLayer;   
     ipGeoDataset = ipFeatureLayer as IGeoDataset;
     ipEnvelope = ipGeoDataset.Extent;   
     ipMaxEnvelope.Union( ipEnvelope);
    }

    m_ipPointToEID = new PointToEIDClass();
    m_ipPointToEID.SourceMap = m_ipMap;
    m_ipPointToEID.GeometricNetwork = m_ipGeometricNetwork;

    double dblWidth = ipMaxEnvelope.Width;
    double dblHeight = ipMaxEnvelope.Height;

    if( dblWidth > dblHeight)
     dblSearchTol = dblWidth / 100;
    else
     dblSearchTol = dblHeight / 100;
    m_ipPointToEID.SnapTolerance = dblSearchTol;

    return true   ;

   }
         
   private void CloseWorkspace()
   {
    m_ipGeometricNetwork = null;
    m_ipPoints = null;
    m_ipPointToEID = null;
    m_ipEnumNetEID_Junctions = null;
    m_ipEnumNetEID_Edges = null;
    m_ipPolyline = null;
   }
  
   #endregion

}
}

备注：

ClsPathFinder   m_ipPathFinder;

if(m_ipPathFinder==null)//打开网络空间
    {
     m_ipPathFinder = new ClsPathFinder();
     ipMap = this.m_ActiveView.FocusMap;
     ipLayer = ipMap.get_Layer(0);
     ipFeatureLayer = ipLayer as IFeatureLayer;
     ipFDB = ipFeatureLayer.FeatureClass.FeatureDataset;
     m_ipPathFinder.SetOrGetMap = ipMap;
     m_ipPathFinder.OpenFeatureDatasetNetwork(ipFDB);
    }

private void ViewMap_OnMouseDown(object sender, ESRI.ARCGIS.MapControl.IMapControlEvents2_OnMouseDownEvent e)//获取鼠标输入的点
   {
    IPoint ipNew ;  
    if( m_ipPoints==null)
    {
     m_ipPoints = new MultipointClass();
     m_ipPathFinder.StopPoints = m_ipPoints;
    }
    ipNew = ViewMap.ActiveView.ScreenDisplay.DisplayTransformation.ToMapPoint(e.x,e.y);
    object o = Type.Missing;
    m_ipPoints.AddPoint(ipNew,ref o,ref o);   
   }

m_ipPathFinder.SolvePath("Weight");//解析路径

IPolyline ipPolyResult = m_ipPathFinder.PathPolyLine();//返回最短路径

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