Quick way to get the contents of a MemoryStream as an ASCII string

I have a JSON string in a MemoryStream. I am using the following code to get it out as an ASCII string:

MemoryStream memstream = new MemoryStream(); 
/* Write a JSON string to memstream here */

byte[] jsonBytes = new byte[memstream.Length];
memstream.Read(jsonBytes, 0, (int)memstream.Length);

string jsonString = Encoding.ASCII.GetString(jsonBytes);

What is a shorter/shortest way to do this?