arcgis server 9.2代码阅读笔记二：在页面上动态加载图层

代码来源 ARCGIS 9.2例子

// Copyright 2006 ESRI
//
// All rights reserved under the copyright laws of the United States
// and applicable international laws, treaties, and conventions.
//
// You may freely redistribute and use this sample code, with or
// without modification, provided you include the original copyright
// notice and use restrictions.
// AUTHER：糊涂虫 2007.9.20
// See use restrictions at /arcgis/developerkit/userestrictions.

using System;
using System.Data;
using System.Configuration;
using System.Web;
using System.Web.Security;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Web.UI.WebControls.WebParts;
using System.Web.UI.HtmlControls;
using ESRI.ArcGIS.Server;
using ESRI.ArcGIS.Utility;
using ESRI.ArcGIS.Carto;
using ESRI.ArcGIS.Geodatabase;
using ESRI.ArcGIS.Geometry;
using ESRI.ArcGIS.Display;

public partial class _Default : System.Web.UI.Page
{
    //创建数据表，用于数据绑定
    DataTable layertable;

    protected void Page_Init(object sender, EventArgs e)
    {
        if (!Page.IsPostBack)
        {
            layertable = new DataTable("layertable");
            DataColumn dc1 = new DataColumn("layername");
            DataColumn dc2 = new DataColumn("layerpath");
            layertable.Columns.Add(dc1);
            layertable.Columns.Add(dc2);
            //读取文件（是一些基本功能）
            String rootPath = Server.MapPath("~");

            System.IO.StreamReader sr = new System.IO.StreamReader(rootPath + "/layers.catalog");
            string delimStr = "=";
            char[] delimiter = delimStr.ToCharArray();
            string[] readparts = null;
            string readstring = null;

            while (sr.Peek() != -1)
            {
                readstring = sr.ReadLine();
                if (!readstring.Contains("="))
                    break;

                readparts = readstring.Split(delimiter);
                DataRow dr = layertable.NewRow();
                dr[0] = readparts[0];
                dr[1] = readparts[1];
                layertable.Rows.Add(dr);
            }
            sr.Close();
        }
    }

    protected void Page_PreRender(object sender, EventArgs e)
    {
        //数据绑定
        DropDownList1.DataSource = layertable;
        DropDownList1.DataTextField = "layername";
        DropDownList1.DataValueField = "layerpath";
        DropDownList1.DataBind();

        if (!Page.IsPostBack)
        {
            if (Session.IsNewSession)
            {
                Session.Add("addedlayers", false);
                Session.Add("addedlayersid", null);
                //创建server上下文
                IServerContext mapContext = this.getServerContext();
                //使用server上下文来定义地图服务
                IMapServer mapServer = mapContext.ServerObject as IMapServer;
                //获得地图服务信息
                IMapServerInfo mapInfo = mapServer.GetServerInfo(mapServer.DefaultMapName);
                //获得地图描述信息
                IMapDescription mapDesc = mapInfo.DefaultMapDescription;
                //放到session中去
                SetSessionMapDescription(mapContext, mapDesc);
                //创建地图
                CreateMapImage(mapContext, mapDesc);
                //释放调server上下文
                mapContext.ReleaseContext();

            }
            else
            {
                IServerContext mapContext = this.getServerContext();
                mapContext = this.getServerContext();

                IMapDescription mapDesc = GetSessionMapDescription(mapContext);
                UpdateDataLayers(mapContext);

                CreateMapImage(mapContext, mapDesc);

                RemoveLayers(mapContext);
                mapContext.ReleaseContext();
            }
        }
        else
        {
            //if a postback, do something here during load
        }
    }

//添加图层
    private void AddTheLayers(IServerContext in_mapcontext)
    {
        IMapServer ms = (IMapServer)in_mapcontext.ServerObject;

        IMapServerObjects2 mso = (IMapServerObjects2)ms;
        string mapname = ms.DefaultMapName;
        IMap map = mso.get_Map(mapname);
        //创建一个新的图层，和它想类似的还有IFeatureClass
        IFeatureLayer layer = (IFeatureLayer)in_mapcontext.CreateObject("esriCarto.FeatureLayer");
        //IFeatureLayer layer = (IFeatureLayer)in_mapcontext.CreateObject("{E663A651-8AAD-11D0-BEC7-00805F7C4268}");
        //创建一个用于打开和创建工作空间的一个工厂接口类
        //IFeatureLayer IFeatureClass IWorkspaceFactory 在AE中都有，他们用于打开和操作数据空间
        IWorkspaceFactory factory = (IWorkspaceFactory)in_mapcontext.CreateObject("esriDataSourcesFile.ShapefileWorkspaceFactory");

        ListItem listitem = DropDownList1.SelectedItem;
        int lastslash = listitem.Value.LastIndexOf("/");
        string filepath = listitem.Value.Substring(0, lastslash);
        string filename = listitem.Value.Substring(lastslash + 1);

        IWorkspace ws = factory.OpenFromFile(filepath, 0);
        IFeatureWorkspace fws = (IFeatureWorkspace)ws;
        layer.FeatureClass = fws.OpenFeatureClass(filename);
        layer.Name = listitem.Text;
        //IGeoFeatureLayer是由IFeatureLayer继承而来，IFeatureLayer是由ILayer继承而来，IGeoFeatureLayer比IFeatureLayer多了标注方面的东西
        IGeoFeatureLayer iglayer = (IGeoFeatureLayer)layer;
        //IFeatureRenderer中定义了一个叫做Draw的方法，其实ArcObjects中各种各样的渲染效果就是通过这个Draw方法画出来的，因为各个渲染效果都实现了IFeatureRenderer接口。所以要实现"GroupRenderer"效果，只要实现了IFeatureRenderer接口就可以了。
        IFeatureRenderer renderer = iglayer.Renderer;
        //创建简单渲染
        ISimpleRenderer isr = (ISimpleRenderer)renderer;
        IRgbColor irgbc = (IRgbColor)in_mapcontext.CreateObject("esriDisplay.RgbColor");
        irgbc.Red = 0;
        irgbc.Green = 0;
        irgbc.Blue = 210;
        //获得类别，各自进行设置。这里比较奇怪的是创建的ifs并没有被添加到图层中去，不是很明白，请教各位。
        ESRI.ArcGIS.Geometry.esriGeometryType featype = layer.FeatureClass.ShapeType;
        if (featype == ESRI.ArcGIS.Geometry.esriGeometryType.esriGeometryPoint)
        {
            ISimpleMarkerSymbol ifs = (ISimpleMarkerSymbol)isr.Symbol;
            ifs.Color = (IColor)irgbc;
        }
        else if (featype == ESRI.ArcGIS.Geometry.esriGeometryType.esriGeometryPolyline)
        {
            ISimpleLineSymbol ifs = (ISimpleLineSymbol)isr.Symbol;
            ifs.Color = (IColor)irgbc;
        }
        else if (featype == ESRI.ArcGIS.Geometry.esriGeometryType.esriGeometryPolygon)
        {
            ISimpleFillSymbol ifs = (ISimpleFillSymbol)isr.Symbol;
            ifs.Color = (IColor)irgbc;
        }
        else
        {
            throw new Exception("No renderer or symbol selected.  Shape type undetermined.");
        }
        //增加图层
        map.AddLayer(layer);
        mso.RefreshServerObjects();

        Session["addedlayersid"] = mso.get_LayerID(mapname, layer);
    }

    private void CreateMapImage(IServerContext mapContext, IMapDescription md)
    {
        //分别创建图像类别 图像描述 图像显示
        IImageType imageType;
        IImageDescription imageDesc;
        IImageDisplay imageDisp;

        imageType = mapContext.CreateObject("esriCarto.ImageType") as IImageType;
        imageDesc = mapContext.CreateObject("esriCarto.ImageDescription") as ImageDescription;
        imageDisp = mapContext.CreateObject("esriCarto.ImageDisplay") as ImageDisplay;
       
        imageType.Format = esriImageFormat.esriImageJPG;
        imageType.ReturnType = esriImageReturnType.esriImageReturnURL;

        imageDisp.Height = (int)imgOutput.Height.Value;
        imageDisp.Width = (int)imgOutput.Width.Value;
        imageDisp.DeviceResolution = 96;

        imageDesc.Display = imageDisp;
        imageDesc.Type = imageType;
        //创建地图服务
        IMapServer mapServer = (IMapServer)mapContext.ServerObject;

        IImageResult mapImage = mapServer.ExportMapImage(md, imageDesc);
        imgOutput.ImageUrl = mapImage.URL;
        imgOutput.Visible = true;

    }
    //创建session
    private void SetSessionMapDescription(IServerContext in_mapcontext, IMapDescription in_mapdesc)
    {
        string md = in_mapcontext.SaveObject(in_mapdesc);
        Session.Add("md", md);
    }
    //获得session
    private IMapDescription GetSessionMapDescription(IServerContext in_mapcontext)
    {
        string stringDesc = Session["md"] as string;
        IMapDescription mapDesc = null;

        if (stringDesc == null)
        {
            IMapServer mapServer = in_mapcontext.ServerObject as IMapServer;
            IMapServerInfo mapInfo = mapServer.GetServerInfo(mapServer.DefaultMapName);
            mapDesc = mapInfo.DefaultMapDescription;
        }
        else
        {
            mapDesc = in_mapcontext.LoadObject(stringDesc) as IMapDescription;
        }

        return mapDesc;
    }
    //创建server上下文，在这个上下文中，运用IServerObjectManager对象管理其生命周期
    private IServerContext getServerContext()
    {
        string servername = "localhost";
        string mapserverobject = "USA_data";
        IServerObjectManager serverManager;

        if (Session["SOM"] == null)
        {
            // *** Using Web ADF Common API
            ESRI.ArcGIS.ADF.Connection.AGS.AGSServerConnection gisconnection = new ESRI.ArcGIS.ADF.Connection.AGS.AGSServerConnection();
            gisconnection.Host = servername;
            gisconnection.Connect();

            serverManager = gisconnection.ServerObjectManager;
            Session.Add("SOM", serverManager);

        }
        else
        {
            serverManager = Session["SOM"] as IServerObjectManager;
        }

        // *** Change the map server object name as needed
        IServerContext mapContext = serverManager.CreateServerContext(mapserverobject, "MapServer");

        return mapContext;

    }

    private void RemoveLayers(IServerContext in_mapcontext)
    {
        //判断是否添加了图层
        bool tf = (bool)Session["addedlayers"];

        if (tf)
        {
            IMapServer ms = (IMapServer)in_mapcontext.ServerObject;

            IMapServerObjects mso = (IMapServerObjects)ms;

            IMap map = mso.get_Map(ms.DefaultMapName);
            //通过地图服务获得图层
            ILayer layer = map.get_Layer(0);

            map.DeleteLayer(layer);
            mso.RefreshServerObjects();
        }
    }

    private void UpdateDataLayers(IServerContext mapContext)
    {
        bool tf = (bool)Session["addedlayers"];

        if (tf)
        {
            AddTheLayers(mapContext);

            // Update dynamic data id, after initial addition of dynamic layer
            IMapDescription mapDesc = GetSessionMapDescription(mapContext);
            ILayerDescription newLayerDesc = mapDesc.LayerDescriptions.get_Element(0);
            newLayerDesc.ID = (int)Session["addedlayersid"];
            SetSessionMapDescription(mapContext, mapDesc);
        }
    }

    protected void btnAddLayer_Click(object sender, EventArgs e)
    {
        Session.Add("addedlayers", true);

        IServerContext mapContext = this.getServerContext();

        UpdateDataLayers(mapContext);

        IMapServer ms = (IMapServer)mapContext.ServerObject;

        IMapServerInfo mapInfo = ms.GetServerInfo(ms.DefaultMapName);

        IMapDescription NEWmapDesc = mapInfo.DefaultMapDescription;

        CreateMapImage(mapContext, NEWmapDesc);

        SetSessionMapDescription(mapContext, NEWmapDesc);

        RemoveLayers(mapContext);

        mapContext.ReleaseContext();

    }

    protected void btnRefresh_Click(object sender, EventArgs e)
    {

        IServerContext mapContext = this.getServerContext();
        UpdateDataLayers(mapContext);

        /*  Test to see actual id of dynamic layer, compare with MapDescription stored in session (also used to generate map image).
         *
        IMapServer ms = (IMapServer)mapContext.ServerObject;           
        IMapServerInfo mapInfo = ms.GetServerInfo(ms.DefaultMapName);           
        IMapDescription NEWmapDesc = mapInfo.DefaultMapDescription;           
        ILayerDescription NEWLayerDesc = NEWmapDesc.LayerDescriptions.get_Element(0);           
        */

        IMapDescription mapDesc = GetSessionMapDescription(mapContext);
        IMapArea mapArea = mapDesc.MapArea;
        //创建IMapExtent  用于描述地图的范围.放大缩小地图
        IMapExtent mapExtent = mapArea as IMapExtent;
        //创建IEnvelope，用来确定一个空间范围，可以做空间查询
        IEnvelope env = (IEnvelope)mapContext.CreateObject("esriGeometry.Envelope");
        env.PutCoords(-120, 30, -50, 50);

        mapExtent.Extent = env;

        CreateMapImage(mapContext, mapDesc);

        SetSessionMapDescription(mapContext, mapDesc);

        RemoveLayers(mapContext);

        mapContext.ReleaseContext();
    }
}

这里比较奇怪的是创建的ifs并没有被添加到图层中去，不是很明白，请教各位。自己现在只是一个初学者，我在这里只是抛砖引玉，希望大家能发出更好的博客文章出来，同时支持原创。如有错误请交流[email protected]。