New Post: ReadMatrix(stream)

I'm trying to use ReadMatrix(stream) and keep getting a null object reference:

        string strData = "3 4 5 6";
        byte[] data = Encoding.ASCII.GetBytes(strData);
        Stream dataStream = new MemoryStream(data, 0, data.Length);
        Matrix<Double> P = mat.ReadMatrix(dataStream);

Can someone suggest how to convert a string to matrix with the ReadMatrix method? Also, how does the method know to make the string above a 1x4 matrix or 2x2?