搜寻与地图上指定点最近的道路节点

private long FindStartLocation()
        {
            long i=0,startLocation=0,listNum=mDataList.Num;
            double minDist=0,tmpDist=0;
            string strStartPoint,tableName="出发地",colName="站名";
            TNode tNode=new TNode();
            strStartPoint=DropDownList1.SelectedItem.ToString();
            MapInfo.Mapping.FeatureLayer fl = (MapInfo.Mapping.FeatureLayer)MapControl1.Map.Layers[tableName];
            MapInfo.Data.Table  t = fl.Table;
            Find find=new Find(t,t.TableInfo.Columns[colName]);
            FindResult findResult=find.Search(strStartPoint);
            tNode.Sx=findResult.FoundPoint.X;
            tNode.Sy=findResult.FoundPoint.Y;
            find.Dispose();
            minDist=dist(tNode,mDataList[i]);
            while(i < listNum)
            {
                if((mDataList[i].Sx==tNode.Sx)&&(mDataList[i].Sy==tNode.Sy))
                {
                    startLocation=i;
                    return startLocation;
                }
                else
                {
                    tmpDist=dist(tNode,mDataList[i]);
                    if(tmpDist < minDist)
                    {
                        minDist=tmpDist;
                        startLocation=i;
                    }

                }
                i++;
            }
            return startLocation;
        }