//从axMapControl控件获取图层

layer = axMapControl.get_Layer(0);//需要的栅格图层

//如果是IRasterLayer图层，将Layer QI至 IRasterLayer

IRasterLayer rasterlayer = layer as IRasterLayer;

// 获得IRaster 接口
IRaster raster = rasterlayer.Raster;

//获取栅格数据波段集
IRasterBandCollection rasterbandcollection = raster as IRasterBandCollection;

//获取指定波段
IRasterBand rasterband = rasterbandcollection.Item(0);
//将波段QI至 IRasterDataset 接口 
IRasterDataset rasterdataset = rasterband as IRasterDataset;