构建网络数据集（c#）

二次开发就是搭积木，但是这种积木在AO中可以成为接口，那么我们二次开发就要想实现我们功能的相关接口组合起来，

ArcGIS中有两种网络，无向网络和有向网络，我在这里讨论是无向网络，网络是用来模拟现实世界中的如交通道路等，这也是GIS中的一个精华，ArcGIS中用一组要素对现实世界中的网络进行抽象，比如用线要素来模拟边，用点要素模拟交汇点等，而网络不是要素，是又相关的要素构建而成的“逻辑图“，所有的分析都是在这个逻辑图上进行的，也可以说这个逻辑图是由相互关联的要素结合一定的规则，派生出来的。而在ArcGIS中无向网络可以有shpfile创建也可以由geodatabase中的数据集创建，而有向网络智能由后者。

对ArcMap的熟练程度有助于我们更快速的开发，我们用网络分析的时候，第一步干什么，第二步干什么……也就是这个流程的熟练程度对我们开发是很有帮助的，下面我们用代码来说明下，因为这个代码很长，我只说明原理等

重要接口Inetworkbuild，利用开发帮助也是一种技巧，这种技巧就好比我们遇到问题了Google下。

步骤一创建网络数据集

IDENetworkDataset deNetworkDataset = new DENetworkDatasetClass();

deNetworkDataset.Buildable = true;

// Open the shapefile and cast to the IGeoDataset interface.

IWorkspaceFactory workspaceFactory = new ShapefileWorkspaceFactoryClass();

IWorkspace workspace = workspaceFactory.OpenFromFile(@

"C:\Program Files\ArcGIS\DeveloperKit\SamplesNET\data\CreateNetworkDataset", 0);

IFeatureWorkspace featureWorkspace = (IFeatureWorkspace)workspace;

IFeatureClass featureClass = featureWorkspace.OpenFeatureClass("Streets");

IGeoDataset geoDataset = (IGeoDataset)featureClass;

IDEGeoDataset deGeoDataset = (IDEGeoDataset)deNetworkDataset;

deGeoDataset.Extent = geoDataset.Extent;

deGeoDataset.SpatialReference = geoDataset.SpatialReference;

// Specify the name of the network dataset.

IDataElement dataElement = (IDataElement)deNetworkDataset;

dataElement.Name = "Streets_ND";

步骤二：

刚才我们创建了网络，但是并没有和相关的要素关联

网络数据集建立了，我们说过网络数据集中应该包含相互关联的要素，而这种主要体现在边和交汇点这两个之上，同时还有一定的规则，比如道路的联通规则，所以我刚才说了逻辑图是由相互关联的要素结合一定的规则，派生出来的

[C#]

// Create a new EdgeFeatureSource object and point it to the Streets shapefile.

IEdgeFeatureSource streetsEdgeFeatureSource = new EdgeFeatureSourceClass();

INetworkSource streetsNetworkSource = (INetworkSource)streetsEdgeFeatureSource;

streetsNetworkSource.Name = "Streets";

streetsNetworkSource.ElementType = esriNetworkElementType.esriNETEdge;

// Set the connectivity settings for the edge feature source.

streetsEdgeFeatureSource.UsesSubtypes = false;

streetsEdgeFeatureSource.ClassConnectivityGroup = 1;

streetsEdgeFeatureSource.ClassConnectivityPolicy =

esriNetworkEdgeConnectivityPolicy.esriNECPEndVertex;

streetsEdgeFeatureSource.FromElevationFieldName = "F_ZLEV";

streetsEdgeFeatureSource.ToElevationFieldName = "T_ZLEV";

ArcGIS的强大在于他能跟准确的模拟这个显示，通过搞成字段可以区分立交桥

步骤三，方向设置

// Create a StreetNameFields object and populate its settings.

IStreetNameFields streetNameFields = new StreetNameFieldsClass();

streetNameFields.Priority = 1; // Priority 1 indicates the primary street name.

streetNameFields.PrefixDirectionFieldName = "PREFIX";

streetNameFields.PrefixTypeFieldName = "PRE_TYPE";

streetNameFields.StreetNameFieldName = "NAME";

streetNameFields.SuffixTypeFieldName = "TYPE";

streetNameFields.SuffixDirectionFieldName = "SUFFIX";

// Add the StreetNameFields object to a new NetworkSourceDirections object,

// then add it to the EdgeFeatureSource created earlier.

INetworkSourceDirections networkSourceDirections = new NetworkSourceDirectionsClass()

;

IArray streetNameFieldsArray = new ArrayClass();

streetNameFieldsArray.Add(streetNameFields);

networkSourceDirections.StreetNameFields = streetNameFieldsArray;

streetsNetworkSource.NetworkSourceDirections = networkSourceDirections;

// Add the EdgeFeatureSource object to the data element as a source in the network dataset.

IArray sourceArray = new ArrayClass();

sourceArray.Add(streetsEdgeFeatureSource);

deNetworkDataset.Sources = sourceArray;

步骤四，可以有turn，也可以没有

步骤五网络权重设置

// Create a new EvaluatedNetworkAttribute object and populate its settings.

IEvaluatedNetworkAttribute minutesEvaluatedNetworkAttribute = new

EvaluatedNetworkAttributeClass();

INetworkAttribute2 minutesNetworkAttribute2 = (INetworkAttribute2)

minutesEvaluatedNetworkAttribute;

minutesNetworkAttribute2.Name = "Minutes";

minutesNetworkAttribute2.UsageType = esriNetworkAttributeUsageType.esriNAUTCost;

minutesNetworkAttribute2.DataType = esriNetworkAttributeDataType.esriNADTDouble;

minutesNetworkAttribute2.Units = esriNetworkAttributeUnits.esriNAUMinutes;

minutesNetworkAttribute2.UseByDefault = true;

// Create evaluator objects and set them on the EvaluatedNetworkAttribute object.

INetworkFieldEvaluator minutesFTNetworkFieldEvaluator = new

NetworkFieldEvaluatorClass();

minutesFTNetworkFieldEvaluator.SetExpression("[FT_Minutes]", "");

INetworkEvaluator minutesFTNetworkEvaluator = (INetworkEvaluator)

minutesFTNetworkFieldEvaluator;

minutesEvaluatedNetworkAttribute.set_Evaluator(streetsNetworkSource,

esriNetworkEdgeDirection.esriNEDAlongDigitized, minutesFTNetworkEvaluator);

INetworkFieldEvaluator minutesTFNetworkFieldEvaluator = new

NetworkFieldEvaluatorClass();

minutesTFNetworkFieldEvaluator.SetExpression("[TF_Minutes]", "");

INetworkEvaluator minutesTFNetworkEvaluator = (INetworkEvaluator)

minutesTFNetworkFieldEvaluator;

minutesEvaluatedNetworkAttribute.set_Evaluator(streetsNetworkSource,

esriNetworkEdgeDirection.esriNEDAgainstDigitized, minutesTFNetworkEvaluator);

INetworkConstantEvaluator minutesNetworkConstantEvaluator = new

NetworkConstantEvaluatorClass();

minutesNetworkConstantEvaluator.ConstantValue = 0;

INetworkEvaluator minutesConstantNetworkEvaluator = (INetworkEvaluator)

minutesNetworkConstantEvaluator;

minutesEvaluatedNetworkAttribute.set_DefaultEvaluator

(esriNetworkElementType.esriNETEdge, minutesConstantNetworkEvaluator);

minutesEvaluatedNetworkAttribute.set_DefaultEvaluator

(esriNetworkElementType.esriNETJunction, minutesConstantNetworkEvaluator);

minutesEvaluatedNetworkAttribute.set_DefaultEvaluator

(esriNetworkElementType.esriNETTurn, minutesConstantNetworkEvaluator);

// Add the attribute to the array.

attributeArray.Add(minutesEvaluatedNetworkAttribute);

步骤六建立网络

// Create a new UID that references the NetworkDatasetWorkspaceExtension.

UID ndWorkspaceExtensionUID = new UIDClass();

ndWorkspaceExtensionUID.Value = "esriGeoDatabase.NetworkDatasetWorkspaceExtension";

// Get the workspace extension and create the network dataset based on the data element.

IWorkspaceExtensionManager workspaceExtensionManager = (IWorkspaceExtensionManager)

workspace;

IWorkspaceExtension workspaceExtension = workspaceExtensionManager.FindExtension

(ndWorkspaceExtensionUID);

IDatasetContainer2 datasetContainer2 = (IDatasetContainer2)workspaceExtension;

IDEDataset deDataset = (IDEDataset)deNetworkDataset;

INetworkDataset networkDataset = (INetworkDataset)datasetContainer2.CreateDataset

(deDataset);

// Once the network dataset is created, build it.

INetworkBuild networkBuild = (INetworkBuild)networkDataset;

networkBuild.BuildNetwork(geoDataset.Extent);