图层渲染（Renderer）

ArcEngine提供多个着色对象用于产生专题图，可以使用标准着色方案，也可以自定义着色方案，ArcEngine提供8中标准着色方案。

一、SimpleRenderer专题图

是使用单一符号进行着色分类，不涉及对要素的数据进行处理。这种专题图同一个图层内的所有元素都是一种符号。

通过SimpleRenderer对象对Symbol进行设置后，赋予IGeoFeatureLayer接口的Renderer属性，对象实现了ITransparencyRenerer接口，通过该接口的属性，可以根据要素的某一个数值字段来设置要素显示的透明度。

该对象还实现了ISimpleRenderer接口，提供了两个重要的属性：Description和Label这两个属性用来设置图例。

/// <summary>
        /// 简单渲染
        /// </summary>
        /// <param name="layerName">图层名字</param>
        /// <param name="FillStyle">FillStyle</param>
        /// <param name="pColor">FillColor</param>
        /// <param name="OutLineColor">OutLineColor</param>
        /// <param name="RenderLabel">样式名称注释</param>
        /// <param name="Descripition">描述</param>
        public void createSimpleFillSymbol(string layerName,esriSimpleFillStyle FillStyle,IColor pColor,IColor OutLineColor,string RenderLabel,string Descripition)
        {
            //简单填充符号
            ISimpleFillSymbol simpleFillSymbol = new SimpleFillSymbolClass();
            //可以用符号选择器进行
            simpleFillSymbol.Style = FillStyle;
            simpleFillSymbol.Color = pColor;
            //创建边线符号
            ISimpleLineSymbol simpleLineSymbol = new SimpleLineSymbolClass();
            simpleLineSymbol.Style = esriSimpleLineStyle.esriSLSSolid;
            simpleLineSymbol.Color = OutLineColor;
            ISymbol symbol = simpleLineSymbol as ISymbol;
            symbol.ROP2 = esriRasterOpCode.esriROPNotXOrPen;
            simpleFillSymbol.Outline = simpleLineSymbol;

            ISimpleRenderer simpleRender = new SimpleRendererClass();
            simpleRender.Symbol = simpleFillSymbol as ISymbol;
            simpleRender.Label = RenderLabel;
            simpleRender.Description = Descripition;

            IGeoFeatureLayer geoFeatureLayer;
            geoFeatureLayer = getGeoLayer(layerName);
            if (geoFeatureLayer != null)
            {
                geoFeatureLayer.Renderer = simpleRender as IFeatureRenderer;
            }
        }

二、ClassBreakRenderer专题图

为分级专题图，通过要素图层中要素的某个数值字段的值，根据用户要求，将这些值分为多个级别，每个级别用不同的Symbol显示。

该对象实现了IClassBreakRenderer接口，提供了实现分级显示的属性和方法，如Field属性用于设置分级着色的字段，BreakCount属性用于设置分级的数目。

/// <summary>
        /// 分级渲染
        /// </summary>
        /// <param name="layerName">图层名</param>
        /// <param name="classCount">分级数目</param>
        /// <param name="ClassField">分级字段</param>
        /// <param name="FillStyle">填充样式</param>
        public void createClassBreakRender(string layerName, int classCount, string ClassField, esriSimpleFillStyle FillStyle)
        {
            //int classCount = 6;
            ITableHistogram tableHistogram;//表格直方图
            IBasicHistogram basicHistogram;//Provides access to members that control histogram objects created from different data sources. 

            ITable table;
            IGeoFeatureLayer geoFeatureLayer;
            geoFeatureLayer = getGeoLayer(layerName);
            ILayer layer = geoFeatureLayer as ILayer;
            table = layer as ITable;
            tableHistogram = new BasicTableHistogramClass();
            //按照 数值字段分级
            tableHistogram.Table = table;
            tableHistogram.Field = ClassField;
            basicHistogram = tableHistogram as IBasicHistogram;
            object values;
            object frequencys;
            //先统计每个值和各个值出现的次数
            basicHistogram.GetHistogram(out values, out frequencys);
            //创建平均分级对象
            IClassifyGEN classifyGEN = new QuantileClass();
            //用统计结果进行分级 ，级别数目为classCount
            classifyGEN.Classify(values, frequencys, ref classCount);
            //获得分级结果,是个 双精度类型数组 
            double[] classes;
            classes = classifyGEN.ClassBreaks as double[];
            //定义不同等级渲染的色带用色
            IEnumColors enumColors = CreateAlgorithmicColorRamp(classes.Length).Colors;
            IColor color;

            IClassBreaksRenderer classBreaksRenderer = new ClassBreaksRendererClass();
            classBreaksRenderer.Field = ClassField;
            classBreaksRenderer.BreakCount = classCount;//分级数目
            classBreaksRenderer.SortClassesAscending = true;//定义分类是否在TOC中显示Legend

            ISimpleFillSymbol simpleFillSymbol;
            for (int i = 0; i < classes.Length - 1; i++)
            {
                color = enumColors.Next();
                simpleFillSymbol = new SimpleFillSymbolClass();
                simpleFillSymbol.Color = color;
                simpleFillSymbol.Style = FillStyle;

                classBreaksRenderer.set_Symbol(i, simpleFillSymbol as ISymbol);
                classBreaksRenderer.set_Break(i, classes[i]);
            }
            if (geoFeatureLayer != null)
            {
                geoFeatureLayer.Renderer = classBreaksRenderer as IFeatureRenderer;
            }
           
        }

三、UniqueValueRenderer专题图

是依据要素图层中的某个字段的不同值，给每个要素一个单独的颜色，以区分存在的每一个要素。

UniqueValueRenderer实现了IUniqueValueRenderer接口，提供了各种属性和方法，如AddValue方法用于将单个要素的某个字段值和与之相匹配的着色符号加入到UniqueValueRenderer对象。

/// <summary>
        /// 单一值渲染（单字段）
        /// </summary>
        /// <param name="layerName">图层名</param>
        /// <param name="RenderField">渲染字段</param>
        /// <param name="FillStyle">填充样式</param>
        /// <param name="valueCount">字段的唯一值个数</param>
        public void createUniqueValueRander(string layerName, string RenderField, esriSimpleFillStyle FillStyle,int valueCount)
        {
            IGeoFeatureLayer geoFeatureLayer;
            geoFeatureLayer = getGeoLayer(layerName);
            IUniqueValueRenderer uniqueValueRenderer = new UniqueValueRendererClass();
            //可以设置多个字段
            uniqueValueRenderer.FieldCount = 1;//0-3个
            uniqueValueRenderer.set_Field(0, RenderField);

            //简单填充符号
            ISimpleFillSymbol simpleFillSymbol = new SimpleFillSymbolClass();
            simpleFillSymbol.Style = FillStyle;

            IFeatureCursor featureCursor = geoFeatureLayer.FeatureClass.Search(null, false);
            IFeature feature;

            if (featureCursor != null)
            {
                IEnumColors enumColors = CreateAlgorithmicColorRamp(valueCount).Colors;
                int fieldIndex = geoFeatureLayer.FeatureClass.Fields.FindField(RenderField);
                for (int i = 0; i < valueCount; i++)
                {
                    feature = featureCursor.NextFeature();
                    string nameValue = feature.get_Value(fieldIndex).ToString();
                    simpleFillSymbol = new SimpleFillSymbolClass();
                    simpleFillSymbol.Color = enumColors.Next();
                    uniqueValueRenderer.AddValue(nameValue, RenderField, simpleFillSymbol as ISymbol);
                }
            }

            geoFeatureLayer.Renderer = uniqueValueRenderer as IFeatureRenderer;
        }
        /// <summary>
        ///  单一值渲染(多字段）
        /// </summary>
        /// <param name="layerName">图层名</param>
        /// <param name="RenderField">多字段名</param>
        /// <param name="FillStyle">样式</param>
        /// <param name="valueCount">每个字段中唯一值的个数</param>
        public void createUniqueValueRander(string layerName, string[] RenderField, esriSimpleFillStyle FillStyle, int[] valueCount)
        {
            IGeoFeatureLayer geoFeatureLayer;
            geoFeatureLayer = getGeoLayer(layerName);
            IUniqueValueRenderer uniqueValueRenderer = new UniqueValueRendererClass();
            //可以设置多个字段
            uniqueValueRenderer.FieldCount = RenderField .Length;//0-3个
            for (int i = 0; i < RenderField.Length; i++)
            {
                uniqueValueRenderer.set_Field(i, RenderField[i]);
            }

            //简单填充符号
            ISimpleFillSymbol simpleFillSymbol = new SimpleFillSymbolClass();
            simpleFillSymbol.Style = FillStyle;

            IFeatureCursor featureCursor = geoFeatureLayer.FeatureClass.Search(null, false);
            IFeature feature;

            if (featureCursor != null)
            {
                for (int i = 0; i < RenderField.Length; i++)
                {
                    IEnumColors enumColors = CreateAlgorithmicColorRamp(valueCount[i]).Colors;
                    int fieldIndex = geoFeatureLayer.FeatureClass.Fields.FindField(RenderField[i]);
                    for (int j = 0; j < valueCount[i]; j++)
                    {
                        feature = featureCursor.NextFeature();
                        string nameValue = feature.get_Value(fieldIndex).ToString();
                        simpleFillSymbol = new SimpleFillSymbolClass();
                        simpleFillSymbol.Color = enumColors.Next();
                        uniqueValueRenderer.AddValue(nameValue, RenderField[i], simpleFillSymbol as ISymbol);
                    }
                }
            }
            geoFeatureLayer.Renderer = uniqueValueRenderer as IFeatureRenderer;
        }

四、ProportionalSymbolRenderer专题图

使用梯度着色法制作的专题图。

ProportionalSymbolRenderer实现了IProportionalSymbolRenderer接口。

这种着色法需要用户知道最大和最小点各自代表的字段值、着色基于的字段和着色点使用的符号以及它在Legend要出现的级别数目。

/// <summary>
        /// 梯度着色
        /// </summary>
        /// <param name="layerName">图层名字</param>
        /// <param name="ProportionField">要参考的字段</param>
        /// <param name="FillStyle">填充样式</param>
        /// <param name="fillColor">填充Color</param>
        /// <param name="characterMarkerSymbol">特征点符号</param>
        /// <param name="units">参考单位</param>
        /// <param name="pLegendSymbolCount">要分成的级数</param>
        public void createProportionSymbolRender(string layerName, string ProportionField, esriSimpleFillStyle FillStyle, IColor fillColor, ICharacterMarkerSymbol characterMarkerSymbol, esriUnits units, int pLegendSymbolCount)
        {
            IGeoFeatureLayer geoFeatureLayer;
            IFeatureLayer featureLayer;
            IProportionalSymbolRenderer proportionalSymbolRenderer;
            ITable table;
            ICursor cursor;
            IDataStatistics dataStatistics;//用一个字段生成统计数据
            IStatisticsResults statisticsResult;//报告统计数据
            //stdole.IFontDisp fontDisp;//定义字体

            geoFeatureLayer = getGeoLayer(layerName);
            featureLayer = geoFeatureLayer as IFeatureLayer;
            table = geoFeatureLayer as ITable;
            cursor = table.Search(null, true);
            dataStatistics = new DataStatisticsClass();
            dataStatistics.Cursor = cursor;
            dataStatistics.Field = ProportionField;//确定分级字段
            statisticsResult = dataStatistics.Statistics;
            if (statisticsResult != null)
            {
                IFillSymbol fillSymbol = new SimpleFillSymbolClass();
                fillSymbol.Color = fillColor;
                //ICharacterMarkerSymbol characterMarkerSymbol = new CharacterMarkerSymbolClass();
                //fontDisp = new stdole.StdFontClass() as stdole.IFontDisp;
                //fontDisp.Name = "arial";
                //fontDisp.Size = 20;
                //characterMarkerSymbol.Font = fontDisp;
                //characterMarkerSymbol.CharacterIndex = 90;
                //characterMarkerSymbol.Color = getRGB(255, 0, 0);
                //characterMarkerSymbol.Size = 8;
                proportionalSymbolRenderer = new ProportionalSymbolRendererClass();
                proportionalSymbolRenderer.ValueUnit = units;
                proportionalSymbolRenderer.Field = ProportionField ;
                proportionalSymbolRenderer.FlanneryCompensation = false;//分级是不是在TOC中显示legend
                proportionalSymbolRenderer.MinDataValue = statisticsResult.Minimum;
                proportionalSymbolRenderer.MaxDataValue = statisticsResult.Maximum;
                proportionalSymbolRenderer.BackgroundSymbol = fillSymbol;
                proportionalSymbolRenderer.MinSymbol = characterMarkerSymbol as ISymbol;
                proportionalSymbolRenderer.LegendSymbolCount = pLegendSymbolCount;//要分成的级数
                proportionalSymbolRenderer.CreateLegendSymbols();
                geoFeatureLayer.Renderer = proportionalSymbolRenderer as IFeatureRenderer;
            }
        }

五、ChartRenderer专题图

使用一个饼图或柱图来表示一个要素的多个属性。有水平排列和累计排列两种。

ChartRenderer对象实现了IChartRenderer接口，其中ChartSymbol方法用于设置着色对象的着色符号，Label属性用于设置Legend的标签。

该方法用于比较一个要素中不同属性，在获得着色图层的单个或多个字段时用RendererField对象来操作。该类实现了IRendererField接口，可以通过AddField方法来添加字段。

该着色法是使用饼图来表现要素的多个属性之间的比率关系。该对象实现了IPicChartRenderer接口，使用PieChartSymbol符号来修饰要素。

/// <summary>
        /// 条状图渲染
        /// </summary>
        /// <param name="layerName">图层名字</param>
        /// <param name="RenderField">要柱状表示的字段</param>
        /// <param name="fillsymbolColor">这些字段分别需要渲染的颜色</param>
        /// <param name="BarWidth">每个柱子的宽度</param>
        /// <param name="BgColor">背景色</param>
        public void createBarChartSymbol(string layerName, string[] RenderField, IColor[] fillsymbolColor,double BarWidth,IColor BgColor)
        {
            IGeoFeatureLayer geoFeatureLayer;
            IFeatureLayer featureLayer;
            ITable table;
            ICursor cursor;
            IRowBuffer rowBuffer;
            //获取渲染图层
            geoFeatureLayer = getGeoLayer(layerName);
            featureLayer = geoFeatureLayer as IFeatureLayer;
            table = featureLayer as ITable;
            geoFeatureLayer.ScaleSymbols = true;
            IChartRenderer chartRenderer = new ChartRendererClass();
            IRendererFields rendererFields = chartRenderer as IRendererFields;
            for (int i = 0; i < RenderField.Length; i++)
            {
                rendererFields.AddField(RenderField[i], RenderField[i]);
            }

            //int[] fieldIndexs = new int[2];
            //fieldIndexs[0] = table.FindField(field1);
            //fieldIndexs[1] = table.FindField(field2);
            //获取要素最大值，决定柱子的最大高度
            double fieldValue = 0.0, maxValue = 0.0;
            cursor = table.Search(null, true);
            rowBuffer = cursor.NextRow();
            while (rowBuffer != null)
            {
                for (int i = 0; i < RenderField.Length; i++)
                {
                    int index = table.FindField(RenderField[i]);
                    fieldValue = double.Parse(rowBuffer.get_Value(index).ToString());
                    if (fieldValue > maxValue)
                    {
                        maxValue = fieldValue;
                    }
                }
                rowBuffer = cursor.NextRow();
            }
            //创建水平排列符号
            IBarChartSymbol barChartSymbol = new BarChartSymbolClass();
            barChartSymbol.Width = BarWidth;//柱子的边长
            IMarkerSymbol markerSymbol = barChartSymbol as IMarkerSymbol;
            markerSymbol.Size = 50;//这个是？
            IChartSymbol chartSymbol = barChartSymbol as IChartSymbol;
            chartSymbol.MaxValue = maxValue;
            //添加渲染符号
            ISymbolArray symbolArray = barChartSymbol as ISymbolArray;
            IFillSymbol[] fillsymbol = new IFillSymbol[RenderField.Length];
            for (int i = 0; i < RenderField.Length; i++)
            {
                //设置不同颜色的柱子
                fillsymbol[i] = new SimpleFillSymbolClass();
                fillsymbol[i].Color = fillsymbolColor[i];
                symbolArray.AddSymbol(fillsymbol[i] as ISymbol);
                //IFillSymbol fillSymbol = new SimpleFillSymbolClass();
                //fillSymbol.Color = getRGB(255, 0, 0);//红色柱子
                //symbolArray.AddSymbol(fillSymbol as ISymbol);
                //fillSymbol = new SimpleFillSymbolClass();
                //fillSymbol.Color = getRGB(0, 255, 0);//绿色柱子
                //symbolArray.AddSymbol(fillSymbol as ISymbol);
            }

            //设置柱状图符号
            chartRenderer.ChartSymbol = barChartSymbol as IChartSymbol;
            //设置底图样式
            IFillSymbol pFillSymbol = new SimpleFillSymbolClass();
            pFillSymbol.Color = BgColor;
            chartRenderer.BaseSymbol = pFillSymbol as ISymbol;
            chartRenderer.UseOverposter = false;//假如那个位置放不下柱状图，是否用线段连接指示位置
            //创建图例
            chartRenderer.CreateLegend();
            geoFeatureLayer.Renderer = chartRenderer as IFeatureRenderer;
        }
        /// <summary>
        /// 创建累计柱状图表（stacked）
        /// </summary>
        /// <param name="layerName">Name</param>
        /// <param name="RenderField">Fields</param>
        /// <param name="fillsymbolColor">every Color</param>
        /// <param name="BarWidth">width</param>
        /// <param name="BgColor">BackGound Color</param>
        public void createStackedChartSymbol(string layerName, string[] RenderField, IColor[] fillsymbolColor, double BarWidth, IColor BgColor)
        {
            IGeoFeatureLayer geoFeatureLayer;
            IFeatureLayer featureLayer;
            ITable table;
            ICursor cursor;
            IRowBuffer rowBuffer;
            //获取渲染图层
            geoFeatureLayer = getGeoLayer(layerName);
            featureLayer = geoFeatureLayer as IFeatureLayer;
            table = featureLayer as ITable;
            geoFeatureLayer.ScaleSymbols = true;
            IChartRenderer chartRenderer = new ChartRendererClass();
            IRendererFields rendererFields = chartRenderer as IRendererFields;
            for (int i = 0; i < RenderField.Length; i++)
            {
                rendererFields.AddField(RenderField[i], RenderField[i]);
            }
            //获取要素最大值
            double fieldValue = 0.0, maxValue = 0.0;
            cursor = table.Search(null, true);
            rowBuffer = cursor.NextRow();
            while (rowBuffer != null)
            {
                for (int i = 0; i < RenderField.Length ; i++)
                {
                    int index = table.FindField(RenderField[i]);
                    fieldValue = double.Parse(rowBuffer.get_Value(index).ToString());
                    if (fieldValue > maxValue)
                    {
                        maxValue = fieldValue;
                    }
                }
                rowBuffer = cursor.NextRow();
            }
            //创建累积排列符号
            IStackedChartSymbol stackedChartSymbol = new StackedChartSymbolClass();

            stackedChartSymbol.Width = 10;//柱子宽度
            IMarkerSymbol markerSymbol = stackedChartSymbol as IMarkerSymbol;
            markerSymbol.Size = 50;//下面的大小
            IChartSymbol chartSymbol = stackedChartSymbol as IChartSymbol;
            chartSymbol.MaxValue = maxValue;
            //添加渲染符号
            ISymbolArray symbolArray = stackedChartSymbol as ISymbolArray;
            IFillSymbol[] fillsymbol = new IFillSymbol[RenderField.Length];
            for (int i = 0; i < RenderField.Length; i++)
            {
                //设置不同颜色的柱子
                fillsymbol[i] = new SimpleFillSymbolClass();
                fillsymbol[i].Color = fillsymbolColor[i];
                symbolArray.AddSymbol(fillsymbol[i] as ISymbol);
            }
            //设置柱状图符号
            chartRenderer.ChartSymbol = stackedChartSymbol as IChartSymbol;
            IFillSymbol pFillSymbol = new SimpleFillSymbolClass();
            pFillSymbol.Color =BgColor;
            chartRenderer.BaseSymbol = pFillSymbol as ISymbol;
            chartRenderer.UseOverposter = false;
            //创建图例
            chartRenderer.CreateLegend();
            geoFeatureLayer.Renderer = chartRenderer as IFeatureRenderer;
        }
        /// <summary>
        /// 创建饼图
        /// </summary>
        /// <param name="layerName">name</param>
        /// <param name="RenderField">Fields</param>
        /// <param name="fillsymbolColor">Each color</param>
        /// <param name="BgColor">background Color</param>
        public void createPieChartSymbol(string layerName, string[] RenderField, IColor[] fillsymbolColor,  IColor BgColor)
        {
            IGeoFeatureLayer geoFeatureLayer;
            IFeatureLayer featureLayer;
            ITable table;
            ICursor cursor;
            IRowBuffer rowBuffer;
            
            //获取渲染图层
            geoFeatureLayer = getGeoLayer(layerName);
            featureLayer = geoFeatureLayer as IFeatureLayer;
            table = featureLayer as ITable;
            geoFeatureLayer.ScaleSymbols = true;
            IChartRenderer chartRenderer = new ChartRendererClass();
            IPieChartRenderer pieChartRenderer = chartRenderer as IPieChartRenderer;
            IRendererFields rendererFields = chartRenderer as IRendererFields;
            for (int i = 0; i < RenderField.Length; i++)
            {
                rendererFields.AddField(RenderField[i], RenderField[i]);
            
            }
            //获取渲染要素的最大值
            double fieldValue = 0.0, maxValue = 0.0;
            cursor = table.Search(null, true);
            rowBuffer = cursor.NextRow();
            while (rowBuffer != null)
            {
                for (int i = 0; i < RenderField.Length ; i++)
                {
                    int index = table.FindField(RenderField[i]);
                    fieldValue = double.Parse(rowBuffer.get_Value(index).ToString());
                    if (fieldValue > maxValue)
                    {
                        maxValue = fieldValue;
                    }
                }
                rowBuffer = cursor.NextRow();
            }
            //设置饼图符号
            IPieChartSymbol pieChartSymbol = new PieChartSymbolClass();
            pieChartSymbol.Clockwise = true;
            pieChartSymbol.UseOutline = true;
            IChartSymbol chartSymbol = pieChartSymbol as IChartSymbol;
            chartSymbol.MaxValue = maxValue;
            ILineSymbol lineSymbol = new SimpleLineSymbolClass();
            lineSymbol.Color = getRGB(255, 0, 0);
            lineSymbol.Width = 2;
            pieChartSymbol.Outline = lineSymbol;
            IMarkerSymbol markerSymbol = pieChartSymbol as IMarkerSymbol;
            markerSymbol.Size = 30;
            //添加渲染符号
            ISymbolArray symbolArray = pieChartSymbol as ISymbolArray;
            IFillSymbol[] fillsymbol =new  IFillSymbol[RenderField.Length];
            for (int i = 0; i < RenderField.Length; i++)
            {
                fillsymbol[i] = new SimpleFillSymbolClass();
                fillsymbol[i].Color = fillsymbolColor[i];
                symbolArray.AddSymbol(fillsymbol[i] as ISymbol);
            }
            //设置背景
            chartRenderer.ChartSymbol = pieChartSymbol as IChartSymbol;
            IFillSymbol pFillSymbol = new SimpleFillSymbolClass();
            pFillSymbol.Color = BgColor;
            chartRenderer.BaseSymbol = pFillSymbol as ISymbol;
            chartRenderer.UseOverposter = false;
            //创建图例
            chartRenderer.CreateLegend();
            geoFeatureLayer.Renderer = chartRenderer as IFeatureRenderer;
        }

六、DotDensityRenderer专题图

DotDensityRenderer对象使用DotDensityFillSymbol符号对Polygon类型的要素进行着色。该专题图使用随机分布的点的密度来表现要素某个属性值得大小。也可以对图层的多个属性值着色，通过指定不同的点符号来区分。

DotDensityRenderer对象实现IDotDensityRenderer接口，定义了使用点密度着色方法和属性，如DotDensitySymbol用于确定着色点符号，CreateLegend方法用于产生图例。

/// <summary>
        /// 点密度
        /// </summary>
        /// <param name="layerName">图层名字</param>
        /// <param name="RenderField">渲染字段</param>
        /// <param name="dotDensityFillSymbol">点密度符号</param>
        /// <param name="simpleMarkerSymbol">点符号</param>
        /// <param name="RenderDensity">点密度</param>
        public void createDotDensityFillSymbol(string layerName, string RenderField, IDotDensityFillSymbol dotDensityFillSymbol, ISimpleMarkerSymbol simpleMarkerSymbol,double  RenderDensity)
        {
            IGeoFeatureLayer geoFeatureLayer;
            IDotDensityRenderer dotDensityRenderer;
            //获取渲染图层
            geoFeatureLayer = getGeoLayer(layerName);
            dotDensityRenderer = new DotDensityRendererClass();
            IRendererFields rendererFields = dotDensityRenderer as IRendererFields;
            //设置渲染字段
            rendererFields.AddField(RenderField, RenderField);

            ////设置填充颜色和背景色,直接由参数传入，具体定义参考下面的 例子
            //dotDensityFillSymbol = new DotDensityFillSymbolClass();
            //dotDensityFillSymbol.DotSize = 3;
            //dotDensityFillSymbol.Color = getRGB(255, 0, 0);
            //dotDensityFillSymbol.BackgroundColor = getRGB(0, 255, 0);

            //设置渲染符号
            ISymbolArray symbolArray = dotDensityFillSymbol as ISymbolArray;
            //点符号样式，也可以参考下面的自己定义
            //ISimpleMarkerSymbol simpleMarkerSymbol = new SimpleMarkerSymbolClass();
            //simpleMarkerSymbol.Style = esriSimpleMarkerStyle.esriSMSCircle;
            //simpleMarkerSymbol.Size = 2;
            //simpleMarkerSymbol.Color = getRGB(0, 0, 255);
            symbolArray.AddSymbol(simpleMarkerSymbol as ISymbol);
            dotDensityRenderer.DotDensitySymbol = dotDensityFillSymbol;
            //设置渲染密度
            dotDensityRenderer.DotValue = RenderDensity;
            //创建图例
            dotDensityRenderer.CreateLegend();
            geoFeatureLayer.Renderer = dotDensityRenderer as IFeatureRenderer;
        }

此外还有两个补充方法（在调用这些方法的时候能用到）：

private IMap pMap;
        public Renderer(IMap _pMap)
        {
            pMap = _pMap;
        }
        //获取颜色对象
        private IRgbColor getRGB(int r, int g, int b)
        {
            IRgbColor pColor;
            pColor = new RgbColorClass();
            pColor.Red = r;
            pColor.Green = g;
            pColor.Blue = b;
            return pColor;
        }
        private IGeoFeatureLayer getGeoLayer(string layerName)
        {
            ILayer layer;
            IGeoFeatureLayer geoFeatureLayer;
            for (int i = 0; i < this.pMap.LayerCount; i++)
            {
                layer = this.pMap.get_Layer(i);
                if (layer != null && layer.Name == layerName)
                {
                    geoFeatureLayer = layer as IGeoFeatureLayer;
                    return geoFeatureLayer;
                }
            }
            return null;
        }