You can use binary writer:
byte[] buffer;
using (IsolatedStorageFile ISF = IsolatedStorageFile.GetUserStoreForApplication())
{
using (IsolatedStorageFileStream FS = new IsolatedStorageFileStream(fileName, FileMode.Create, ISF))
{
using (BinaryWriter BW = new BinaryWriter(FS))
{
BW.Write(buffer, 0, buffer.Lenght);
}
}
}
Or make it simpler as @KooKiz said:
using (IsolatedStorageFileStream FS = new IsolatedStorageFileStream(fileName, FileMode.Create, ISF))
{
FS.Write(buffer, 0, buffer.Lenght);
}