IRaster、IRasterlayer、IRasterdataset之间的转换
layer = axMapControl.get_Layer(0);//需要的栅格图层
IRasterLayer rasterlayer = layer as IRasterLayer;
IRaster raster = rasterlayer.Raster;
IRasterBandCollection rasterbandcollection = raster as IRasterBandCollection;
IRasterBand rasterband = rasterbandcollection.Item(0);
IRasterDataset rasterdataset = rasterband as IRasterDataset;
from：http://hi.baidu.com/cya_lm/item/6f2fbceb33f3510a4ddcaf43