Streaming response from ASP.NET with end-of-stream calculated properties

Question

I was pleasantly surprised to learn that this works as a streamable response in ASP.NET:

MapGet("/", GetStream);

private static Wrapper GetStream()
{
    var stream = CreateStream();
    return new Wrapper
    {
        Data = stream,
        Cursor = ""
    };
}

private static async IAsyncEnumerable<int> CreateStream()
{
    for (var i = 0; i < 5; i += 1)
    {
        yield return i;
        await Task.Delay(1000);
    }
}

class Wrapper
{
    public IAsyncEnumerable<int> Data { get; set; }
    public string Cursor { get; set; }
}

i.e. if you request this, the response will be streamed in parts, e.g.: { "data": [0, 1, 2 until it finally completes, e.g. { "data": [0, 1, 2, 3, 4], "cursor": "" }

However, is there a way to defer the population of one of these properties - in this case my Cursor property - until the stream has completed? For example, in this case I'd want to set the cursor to the something calculated from the final data item that was emitted.