convert string to memory stream – Memory stream is not expandable?

The following code works correctly for me

public class Foo
{
    public static void Main()
    {
        var myPage = "test string";
        var repo =  new System.IO.MemoryStream(System.Text.Encoding.UTF8.GetBytes(myPage));
    }
}

It seems that the correct way to do this is to create the MemoryStream using the default constructor

var repo = new System.IO.MemoryStream();

and then write to it

var stringBytes = System.Text.Encoding.UTF8.GetBytes(myPage);
repo.Write(stringBytes, 0, stringBytes.Length);

if you want to be able to read the stream as normal (eg using a StreamReader) then you will also need to call:

repo.Seek(0, SeekOrigin.Begin);