SlackTaskClient.DeleteMessageAsync takes a datetime but should take a timestamp string

[mdiluz]

DeleteMessageAsync for the task client seems to be written to match the one in the socket client, which understands timestamps as date times, but the API requires the timestamp as a string including microseconds.

Demonstrated in code below:

var response = await SlackTaskClient.PostMessageAsync(recipient, item.Message);
if (!response.ok)
    throw new Exception(response.error);

// response.ts e.g. 1645450156.370359
var baseTimestamp = response.ts.Replace(".",""); // Remove the bullet point
var ts = long.Parse(baseTimestamp) / 1000; // Problem: We have to lose the milliseconds here
var time = DateTimeOffset.FromUnixTimeMilliseconds(ts).DateTime; // Convert to a DateTime

var deletedResponse = await SlackTaskClient.DeleteMessageAsync(response.channel, time); 
if (!deletedResponse.ok)
    throw new Exception(deletedResponse.error); // We fail with message_not_found

Slack needs the full ts string with the unique digits after the ., not a real timestamp, so DeleteMessageAsync can't work here as I don't think you can stick the microseconds back into a DateTime (and I don't think ToProperTimeStamp can convert and add the .).

The workaround for now is simply to make the call manually:

var deletedResponse = await SlackTaskClient.APIRequestWithTokenAsync<DeletedResponse>(new List<Tuple<string, string>>()
{
    new("ts", response.ts),
    new("channel", response.channel)
}.ToArray());

if (!deletedResponse.ok)
    throw new Exception(deletedResponse.error);

[ceciliachan1979]

@mdiluz This will preserve the milliseconds.

            decimal doubleTimestamp = Decimal.Parse(response.ts);
            long longTimestamp = (long)(doubleTimestamp * 10000000m);
            DateTime unixEpoch = new DateTime(1970, 1, 1, 0, 0, 0, 0, DateTimeKind.Utc);
            return unixEpoch.AddTicks(longTimestamp);

There are other APIs (such as GetConversationsHistoryAsync) that return timestamps as DateTime, maybe we can consider changing PostMessageAsync to return DateTime instead?