Thanks Nahed! I saw that solution on the website. But May be it is not the end result. My code is as following.
public IRaster RasterClip (IRasterLayer pRasterLayer, IEnvelope pExtent)
IRaster pRaster = pRasterLayer.Raster;
IRasterProps pProps = pRaster as IRasterProps;
object cellSizeProvider = pProps.MeanCellSize().X;
IGeoDataset pInputDataset = pRaster as IGeoDataset;
IGeoDataset pOutputDataset = pTransformionOp.Clip(pInputDataset, pExtent);
clipRaster = pOutputDataset as IRaster;