arcgis engine在地图上点击某条河流，做出这条河流的缓冲区代码实现

以下是使用 ArcGIS Engine 实现点击某条河流生成缓冲区的代码：

1. 在 ArcMap 中创建一个地图文档并加载需要的河流图层。

2. 在 Visual Studio 中创建一个 ArcGIS Engine 的 Windows 窗体应用程序。

3. 将 AxMapControl 控件拖放到窗体上，并设置其 Dock 属性为 Fill。

4. 添加以下引用：

using ESRI.ArcGIS.Carto;
using ESRI.ArcGIS.Geometry;
using ESRI.ArcGIS.Controls;
using ESRI.ArcGIS.SystemUI;
using ESRI.ArcGIS.Display;

5. 在窗体的 Load 事件中初始化地图和河流图层：

private void Form1_Load(object sender, EventArgs e)
{
    // 初始化地图控件
    axMapControl1.Map.ClearLayers();
    axMapControl1.Map.AddLayer(CreateFeatureLayer(@"path\to\river.shp"));

    // 设置地图文档路径
    axMapControl1.MapDocumentFilename = @"path\to\map.mxd";

    // 刷新地图
    axMapControl1.Refresh();
}

// 创建要素图层
private IFeatureLayer CreateFeatureLayer(string path)
{
    // 打开 Shapefile
    IWorkspaceFactory workspaceFactory = new ShapefileWorkspaceFactoryClass();
    IWorkspace workspace = workspaceFactory.OpenFromFile(System.IO.Path.GetDirectoryName(path), 0);
    IFeatureWorkspace featureWorkspace = workspace as IFeatureWorkspace;
    IFeatureClass featureClass = featureWorkspace.OpenFeatureClass(System.IO.Path.GetFileName(path));

    // 创建要素图层
    IFeatureLayer featureLayer = new FeatureLayerClass();
    featureLayer.FeatureClass = featureClass;
    featureLayer.Name = featureClass.AliasName;

    return featureLayer;
}

6. 在 axMapControl1_OnMouseDown 事件中实现点击河流生成缓冲区：

private void axMapControl1_OnMouseDown(object sender, IMapControlEvents2_OnMouseDownEvent e)
{
    // 获取当前点击的河流要素
    IFeatureLayer riverLayer = GetFeatureLayerByName("river");
    IFeature riverFeature = GetSelectedFeature(riverLayer, e.mapX, e.mapY);

    if (riverFeature == null)
    {
        return;
    }

    // 生成缓冲区并添加到地图上
    IGeometry bufferGeometry = CreateBuffer(riverFeature.ShapeCopy, 100); // 缓冲区半径为 100 米
    AddGraphicToMap(bufferGeometry);
}

// 根据名称获取要素图层
private IFeatureLayer GetFeatureLayerByName(string name)
{
    ILayer layer = null;
    for (int i = 0; i < axMapControl1.Map.LayerCount; i++)
    {
        layer = axMapControl1.Map.get_Layer(i);
        if (layer is IFeatureLayer && layer.Name.ToLower() == name.ToLower())
        {
            return layer as IFeatureLayer;
        }
    }
    return null;
}

// 获取选中的要素
private IFeature GetSelectedFeature(IFeatureLayer featureLayer, double x, double y)
{
    IPoint point = new PointClass();
    point.PutCoords(x, y);

    // 创建查询过滤器
    ISpatialFilter spatialFilter = new SpatialFilterClass();
    spatialFilter.Geometry = point;
    spatialFilter.SpatialRel = esriSpatialRelEnum.esriSpatialRelIntersects;

    // 查询要素
    IFeatureCursor featureCursor = featureLayer.Search(spatialFilter, false);
    IFeature feature = featureCursor.NextFeature();

    return feature;
}

// 创建缓冲区
private IGeometry CreateBuffer(IGeometry geometry, double distance)
{
    ITopologicalOperator topologicalOperator = geometry as ITopologicalOperator;
    IGeometry bufferGeometry = topologicalOperator.Buffer(distance);

    return bufferGeometry;
}

// 将图形添加到地图上
private void AddGraphicToMap(IGeometry geometry)
{
    IGraphicsContainer graphicsContainer = axMapControl1.Map as IGraphicsContainer;
    IElement element = new PolygonElementClass();
    element.Geometry = geometry;
    graphicsContainer.AddElement(element, 0);
    axMapControl1.Refresh(esriViewDrawPhase.esriViewGraphics, null, null);
}

注：以上代码中的“river”为河流图层的名称，需要根据实际情况进行修改。