decompressing LZ4 compressed string using lz4net

Question

I want to decompress a LZ4 encoded string using the lz4net library available from NuGet https://www.nuget.org/packages/lz4net/, the GitHub site for this library is https://github.com/MiloszKrajewski/lz4net.

I'm not familiar with streams nor this library, but here is my code so far:

Private Function LZ4Decompress(input As String) As String
    Dim inputBytes() As Byte = System.Text.Encoding.Unicode.GetBytes(input)

    Dim inputStream As New MemoryStream()
    inputStream.Write(inputBytes, 0, inputBytes.Length)
    inputStream.Seek(0, SeekOrigin.Begin)

    Dim outputStream As New MemoryStream()
    Dim outputBytes(1024) As Byte
    Dim output As String

    Using lzStream As New LZ4.LZ4Stream(inputStream, LZ4.LZ4StreamMode.Decompress)
        ' how to write to outputStream ?
    End Using

    outputStream.Read(outputBytes, 0, outputStream.Length)
    output = System.Text.Encoding.Unicode.GetString(outputBytes)
    Return output
End Function

Issues:

1. lzStream has a length of -1 so I can't read from it, how do I do that?
2. I can only instantiate outputBytes with a fixed length, I'd like to make it just as large as required