Linqpad Intellisense very slow

Linqpad intellisense on my Win 10 laptop has been extremely slow for me recently. I just installed the latest beta v5.33.09 (AnyCPU) in the hopes that it would resolve the issue, but to no avail.

I mostly use LinqPad as a scratchpad to test small pieces of code or expressions. There are no database connections being made. I'm simply running the "C# Program" profile. When I write "var" to start my first line of code, the intellisense kicks off and just hangs there for a few seconds. It's making this product quite unusable.

Any recommendations as to what I should do to help resolve this? I've never encountered this in previous iterations.


  • I've just uploaded a new beta (5.33.10) with an embedded profiler.

    Go to Help | About and click "Start internal profiling". Then create a query, type "var" or whatever causes it to hang, go back to Help | About, and click the link again to stop profiling and display the file containing the results. Could you please send me the file (support at linq pad dot net).

  • Thank you for the quick turnaround. I've sent the perf file.
  • Thanks for the file. Does this slowdown happen right after starting LINQPad, or a few hours or so later?

    And can you reproduce it on another machine?
  • The slowdown happens right after starting. I am not able to reproduce this on another machine, but I'm at a loss as to what is causing it on my development laptop.
  • Hi, I'm also experiencing this thing but I think I have some additional information.

    I'm using a MS Surface Pro 4, Core i7-6650U model with Surface Hub into which I connect an HD monitor and a 4k monitor (running at 150% scale).

    I first started experiencing graphical weirdness after one of the larger recent windows updates, a few months ago, roughly when Meltdown and Spectre were in the news.

    The problem in LINQPad is as described by cabraham except I type "Dim x" (which takes >10sec). I've also experienced similar weirdness in Excel and Tortoise SVN.

    Here's the weird part. As soon as I disconnect my 4k monitor all the problems disappear, I don't even have to restart my LINQPad. As soon as I reconnect it the problem begins. It doesn't seem to matter which screen LINQPad is running on.

    This is clearly a windows problem, probably GDI or DWM. I'll send perf logs in a moment.
  • edited September 11
    Your logs indicate as similar stack trace as cabraham - It's getting stuck on the GDI+ DrawRectangle function.

    I've dug through the syntax editor source code and have identified a bug in not disposing a GDI+ pen. There's a small chance that it's related to this - if so, you'll find it fixed in the 5.33.11 beta. It's worth a try; otherwise as you say, it will be something inside Windows which will be hard to track down.
  • Thanks for the speedy effort!

    The version I tried earlier when I sent the perf logs was also 5.33.11 - did you update it but kept the version the same? Anyway, I redownloaded 5.33.11 AnyCpu, unfortunately the problem persists. For now I'm working around the problem by switching off "Show completion list after typing a letter" and using Ctrl+Space when I need it. Hopefully one of the coming windows updates will resolve this.

    PS: LinqPad is my bread and butter and I insist that everyone I work with install it, thank you for this little gem.
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