IRasterBandCollection pRasterBandCollection = pRasterDataset as IRasterBandCollection;
IRasterBand pRasterBand = pRasterBandCollection.Item(0);
 IRaster pRaster = (pRasterDataset as IRasterDataset2).CreateFullRaster();
IRawPixels pRawPixels = pRasterBand as IRawPixels;
IRasterProps pRasterProps = pRasterBand as IRasterProps;
int dHeight = pRasterProps.Height;
int dWidth = pRasterProps.Width; 
IPnt pntSize = new PntClass();
pntSize.SetCoords(dHeight, dWidth);
IPnt pPixelBlockOrigin = new PntClass();
pPixelBlockOrigin.SetCoords(0, 0);
IPixelBlock pixelBlock = pRaster.CreatePixelBlock(pntSize);
pRawPixels.Read(pPixelBlockOrigin, pixelBlock);
System.Array arr = (System.Array)(pixelBlock as IPixelBlock3).get_PixelData(0);
for (int i = 0; i < dHeight;i++ ) 
{
 for (int j = 0; j < dWidth; j++) 
 {
   float number = 0;
   float.TryParse(arr.GetValue(i,j).ToString(),out number);     
  }
}