C# write binary to file

FileInfo fileInfo = new FileInfo(filenamePath);

if (!IsExistsDirectory(fileInfo.DirectoryName))

{

CreateDirectory(fileInfo.DirectoryName);

}

FileStream fs = new FileStream(filenamePath, FileMode.Create, FileAccess.Write);

using (BinaryWriter bw = new BinaryWriter(fs))

{

bw.Write(buff);

}