AspNet Core 3.1 Razor compilation extremely slow (dozen of minutes) for a view with big static html table

I’ve updated an asp.net core 2.2 mvc website to core 3.1 and found razor compilation extremely slow. I’m talking dozen of minutes! After a couple of hours I’ve found the problem: I had a 5Mb razor view with a big static html table containing 9300 rows. I know this may not be a common scenario but the performance degradation - comparing to netcore 2.2 - is not acceptable and certainly deserves improvement.

I was able to reproduce just creating a new asp.net core 3.1 mvc project and adding the html table to the Home/Index.cshtml

• ASP.NET Core version: 3.1
• Visual Studio 2019 version 16.4.1

dotnet --info output:

.NET Core SDK (reflecting any global.json): Version: 3.1.100 Commit: cd82f021f4

Runtime Environment: OS Name: Windows OS Version: 10.0.18363 OS Platform: Windows RID: win10-x64 Base Path: C:\Program Files\dotnet\sdk\3.1.100\

Host (useful for support): Version: 3.1.0 Commit: 65f04fb6db

.NET Core SDKs installed: 2.2.402 [C:\Program Files\dotnet\sdk] 3.1.100 [C:\Program Files\dotnet\sdk]

.NET Core runtimes installed: Microsoft.AspNetCore.All 2.1.0 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.All] Microsoft.AspNetCore.All 2.1.1 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.All] Microsoft.AspNetCore.All 2.1.2 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.All] Microsoft.AspNetCore.All 2.1.14 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.All] Microsoft.AspNetCore.All 2.2.7 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.All] Microsoft.AspNetCore.All 2.2.8 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.All] Microsoft.AspNetCore.App 2.1.0 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App] Microsoft.AspNetCore.App 2.1.1 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App] Microsoft.AspNetCore.App 2.1.2 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App] Microsoft.AspNetCore.App 2.1.14 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App] Microsoft.AspNetCore.App 2.2.7 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App] Microsoft.AspNetCore.App 2.2.8 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App] Microsoft.AspNetCore.App 3.1.0 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App] Microsoft.NETCore.App 2.0.0 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App] Microsoft.NETCore.App 2.1.14 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App] Microsoft.NETCore.App 2.2.7 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App] Microsoft.NETCore.App 2.2.8 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App] Microsoft.NETCore.App 3.1.0 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App] Microsoft.WindowsDesktop.App 3.1.0 [C:\Program Files\dotnet\shared\Microsoft.WindowsDesktop.App]

[moxplod]

Hi @mkArtakMSFT here is a page load time - 18ms when razor is compiled. And I add single whitespace in the razor page and refresh, it takes around 10s in most cases. Some cases I have seen much higher. Trying to figure out how to send you a repro project.

In 2.2 it was definitely not noticeable like this, but do not have the time taken there recorded.

[ajaybhargavb]

@agrinei, thanks for the report. You can unblock yourself in the mean time by doing one of the following,

Option 1

Move the large static table to a separate .html file and then do,

@Html.Raw(System.IO.File.ReadAllText("Path/to/table.html"))

Option 2

Move the contents inside a script tag and embed it as a string,

<div id="mytable"></div>
<script>
    var tabledata = `
<table>
  <tr>...</tr>
  <tr>... </tr>
  ...
</table>
`;

    document.getElementById('mytable').innerHTML = tabledata;
</script>