If you've tried using a DataContractJsonSerializer or a DataContractSerializer with Push Notification for the Windows Phone, you may have experienced an ArgumentNullException during deserialization. This can happen because the MemoryStream is buffered with null characters '\0' that prevent deserialization. A solution is to create a new array and copy all bytes except for the trailing nulls, as shown in the following excerpt from the downloadable sample code in my upcoming book Windows Phone 7 Unleashed:

using (BinaryReader reader = new BinaryReader(bodyStream))
{
byte[] bodyBytes = reader.ReadBytes((int)bodyStream.Length);

int lengthWithoutNulls = bodyBytes.Length;
for (int i = bodyBytes.Length - 1; i >= 0 && bodyBytes[i] == '\0'
i--, lengthWithoutNulls--)
{
/* Intentionally left blank. */
}

byte[] cleanedBytes = new byte[lengthWithoutNulls];
Array.Copy(bodyBytes, cleanedBytes, lengthWithoutNulls);

DataContractJsonSerializer serializer
new DataContractJsonSerializer(typeof(StockQuote));

using (MemoryStream stream = new MemoryStream(cleanedBytes))
{
StockQuote = (StockQuote)serializer.ReadObject(stream);
}
}

Have a great day!