blazor localStorage F5 Refresh “Object reference not set to an instance of an object.”

[scalablecory]

From @azbo on Wednesday, September 18, 2019 6:31:28 AM

Issue Title

blazor localStorage F5 Refresh “Object reference not set to an instance of an object.”

General

visual studio version:

sdk version:.net core sdk 3.0 rc1

localStorage get set js:

Index.razor set localStorage:

Counter.razor get localStorage:

Reiteration steps：
step1:

step2:

step3:
F5 Refresh or

step4 except:

Copied from original issue: dotnet/core#3394

[javiercn]

@scalablecory You are trying to perform JS interop during OnInitializedAsync which is not supported and might not work well in all scenarios. The right place to do JS interop (where is safe to do so) is inside OnAfterRenderAsync

What is happening is that during prerendering the JS runtime is not initialized, so you get an error when you try to prerender the Counter page. It doesn't happen when you are launching the app because you are prerendering the Index page, but when you go to the counter page and press F5 it tries to prerender the Counter page and fails at that point.

[pranavkm]

@azbo this is a dup of #13396. We'll use the other issue to track fixing this in 3.1. In the meanwhile, @javiercn's recommendation is correct.