IE11 support for server-side Blazor

[zerocore2340]

Creating a default "Razor Component" Project and trying to access it from IE 11 doesn't seem to work.

Steps to reproduce the behavior:

1. Create a new "Razor Component" project
2. Run
3. Access it from IE11

Expected behavior / Error
The counter page shows up but the button action does not do anything .

IE11 Console shows the following error during the load of the page

• Promise is undefined

I tried to do random stuff that got me nowhere.

I added <script src="https://cdnjs.cloudflare.com/ajax/libs/bluebird/3.3.5/bluebird.min.js"></script>

then I got "fetch is undefined"
So I added <script src="https://cdnjs.cloudflare.com/ajax/libs/fetch/2.0.3/fetch.js"></script>

and now I get-
undefined is not encodable in msgpack!

[springy76]

Some doc/wiki page once mentioned you'll need polyfills. I tried some in the past without success.

[isc30]

1. get https://github.com/Daddoon/Blazor.Polyfill
2. include it before blazor script tag
3. profit

[springy76]

I already tried that one. While it works for simple setups like the counter page, my stress test page (which I made for #6385) just never changes from "loading..." to final values: https://github.com/springy76/RazorComponentsProblems/blob/problem/ConnectionDiesWhenUsingAsyncOperations/WebApp/Components/Pages/Index.razor (and so does the real real world app which we're migrating to Razor components).

[isc30]

That's an interesting edge case, I'll try to have a look and try to catch the errors there.
Does the console show any error?

[springy76]

The console only shows timeout after 30s. But I have to revaluate because on my home machine the sample even crashes on Firefox earlier than expected. Maybe I hit the "MessagePack's ReadStringSlow looks broken" problem SteveSandersonMS has mentioned.

[isc30]

yeah, that sounds more like a bug in the message queue than in the browser.

Answering the original question (ie11 polyfills), the mentioned library seems to work well on normal use cases

[mkArtakMSFT]

@javiercn can you please have a look at this and see what prevents us from supporting IE11? Thanks!