Charts disappear immediately after being displayed.

guyoliver

I'm seeing a weird behavior I'm trying to make sense of, and I'm hoping someone here might have some insight.

I should start by saying that if I load up the samples Charting examples in linqpad 5 or 6 and run them things work fine. The charts display and everything is as expected. The behavior described below happens in both of the most recent versions of linqpad 5 and 6.

I recently created a linqpad doc that connected to an influxdb instance, fetched a set of data through a query, turned it into a list of anonymous records, and then I tried to chart it with a fairly simple .Chart() and .Dump() call. The behavior I see is that the chart is displayed, no errors are shown, but then just a few brief moments later, the chart tab clears to a default background.

DumpInline() works fine. And .Dump() works fine in the simpler cases shown in the samples where the data is all local arrays.

I don't think I missed anything in the documentation about how to use chart, but I'm hoping someone will point out what I am doing wrong.

---

EDIT I just found something that may help explain something. I ran this one last time, this time as a non maximized window (I was thinking of capturing it as a gif to include here), and saw the same thing as before, the chart content disappears. But then I moved the linqpad window and the chart is there - floating on my desktop behind the linqpad instance. This is starting to smell like a bug, and not user error - has anyone else seen this?

I don't know if it matters but this is all being done through a remote desktop session as I can't access the influxdb from where I am. I have a vague memory of rdp having an effect on how graphics operations are carried out, at least in the distant past.

---

The document in question looks like the below:

<Query Kind="Statements">
  <NuGetReference>Vibrant.InfluxDB.Client</NuGetReference>
  <Namespace>Vibrant.InfluxDB.Client</Namespace>
  <Namespace>Vibrant.InfluxDB.Client.Rows</Namespace>
  <RemoveNamespace>System.Collections</RemoveNamespace>
  <RemoveNamespace>System.Collections.Generic</RemoveNamespace>
  <RemoveNamespace>System.Data</RemoveNamespace>
  <RemoveNamespace>System.Diagnostics</RemoveNamespace>
  <RemoveNamespace>System.IO</RemoveNamespace>
  <RemoveNamespace>System.Linq.Expressions</RemoveNamespace>
  <RemoveNamespace>System.Reflection</RemoveNamespace>
  <RemoveNamespace>System.Text</RemoveNamespace>
  <RemoveNamespace>System.Text.RegularExpressions</RemoveNamespace>
  <RemoveNamespace>System.Threading</RemoveNamespace>
  <RemoveNamespace>System.Transactions</RemoveNamespace>
  <RemoveNamespace>System.Xml</RemoveNamespace>
  <RemoveNamespace>System.Xml.Linq</RemoveNamespace>
  <RemoveNamespace>System.Xml.XPath</RemoveNamespace>
</Query>


using var client = new InfluxClient(new Uri("http://server:8086"));

var res = await client.ReadAsync<DynamicInfluxRow>("logs", @"
    select count(Assembly) from logs.autogen.Logs where 
    and time >= '2019-12-04'
    and level = 'Error' 
    group by time(1d)
");

var data = res.Results[0].Series[0].Rows.Select(item => new { item.Timestamp, Value = item  .Fields["count"]}).ToList();

data.Chart(c => c.Timestamp).AddYSeries(c => c.Value, LINQPad.Util.SeriesType.Line).Dump();

JoeAlbahari

Do you get the same problem if you run the following query:

"GridTest".ToCharArray().Dump(true);

guyoliver

That works fine, on Linqpad 5 and 6, both on my local machine and over the RDP session I used earlier.

below is a screen capture of what happens with the original influxdb generated graph.

---

I have tried to recreate this with simpler scripts, for instance, just plotting a bunch of timestamped random values and that works perfectly.

var rand = new Random();

Enumerable.Range(0, 1000)
    .Select(x => new {
        Timestamp = DateTime.Now + TimeSpan.FromSeconds(x), 
        Value = Math.Sin(x)
    })
    .Chart(x => x.Timestamp, x => x.Value)
    .Dump();

That is as far as I can see basically the same plotting as in the one that acts weird. Makes me think that something about the actual running of the query is introducing the issue, but I don't have any idea how.

guyoliver

Update -

If I put your GridTest test after the original Chart().Dump() calls, then they both disapear and end up floating off screen. But only when the influxdb calls are there, if its just a plot or a gridtest by itself, it works fine.

JoeAlbahari

Is there anything relevant in %localappdata%\linqpad\Logs.LINQPad6\logs.txt?

I suspect the charting control is throwing some kind of exception or hanging in a way that prevents LINQPad from sizing and positioning its form.

guyoliver

I'm afraid not. That folder is empty after running the query in question. Sorry.

nickoli

I too am experiencing this issue. Maybe it has something to do with async/await? I'm calling a weather api with the HttpClient using async/await and parsing the results using System.Text.Json.JsonSerializer using async/await. But, if I remove the async Task from the Main method and call .Result from my async call, the chart shows just fine.
Nothing in the logs for me either, unfortunately.

I was able to reproduce the issue using this code:

async Task Main()
{
    await Task.Delay(2000);
    var customers = new[]
    {
        new { Name = "John", TotalOrders = 100 },
        new { Name = "Mary", TotalOrders = 130 },
        new { Name = "Sara", TotalOrders = 140 },
        new { Name = "Paul", TotalOrders = 125 },
    };

    customers.Chart(c => c.Name, c => c.TotalOrders).Dump();   // Don't forget to Dump it!
}

JoeAlbahari

This is a different problem: the controls end up being created on a non-UI thread after awaiting. You can fix it by adding the following code to your query before awaiting:

Util.CreateSynchronizationContext();

nickoli

That solved it. Thank you!