设置图层符号风格为用已有mxd里的同名图层风格

 //要加载的IFeatureClass
 IFeatureClass pFeatClass = dataset as IFeatureClass;
 //新建要加载到mxd文档中的图层
 IFeatureLayer pFeatLayer = new FeatureLayerClass();
 //设置新加图层的要素类
 pFeatLayer.FeatureClass = pFeatClass;
 //设置新家图层的名称
 pFeatLayer.Name = pFeatClass.AliasName;
 //GetRenderLayer函数实现从已配置好符号风格的mxd文档中的同名图层
 IGeoFeatureLayer pGeoLayer = GetRenderLayer(pFeatClass.AliasName) as IGeoFeatureLayer;
 //定义新加载图层为IGeoFeatureLayer类
 IGeoFeatureLayer pNewGeolayer = pFeatLayer as IGeoFeatureLayer;
 //为新加载图层设置符号风格
 pNewGeolayer.Renderer = pGeoLayer.Renderer;

此功能适用于固定显示风格的成图加载等。