求GIS点密度渲染的代码（C#）

如果你给分的话 分肯定是我的

IDotDensityRenderer pDotDensityRenderer = new DotDensityRendererClass();
IRendererFields pRendererFields =(IRendererFields) pDotDensityRenderer;
pRendererFields.AddField( "POP1990","1990年人口");

IDotDensityFillSymbol pDotDensityFillSymbol = new DotDensityFillSymbolClass();
pDotDensityFillSymbol.DotSize = 1;
pDotDensityFillSymbol.Color = GetRGBColor(0, 0, 0);
pDotDensityFillSymbol.BackgroundColor = GetRGBColor(239, 228, 190); // color of tan

ISymbolArray pSymbolArray =(ISymbolArray) pDotDensityFillSymbol;
ISimpleMarkerSymbol pMarkerSymbol = new SimpleMarkerSymbolClass();

pMarkerSymbol.Style =esriSimpleMarkerStyle.esriSMSCircle ;
pMarkerSymbol.Size = 3;
pMarkerSymbol.Color = GetRGBColor(0, 0, 0); // Black
pSymbolArray.AddSymbol((ISymbol) pMarkerSymbol);

pDotDensityRenderer.DotDensitySymbol = pDotDensityFillSym