Aspnetcore: Case-sensitive misspelled names and also missing namespaces cause a misleading error

[tomRedox]

I just switched from Preview 6 to 8 and started getting lots of this error:

The attribute names could not be inferred from bind attribute 'bind-value'. Bind attributes should be of the form 'bind' or 'bind-value' along with their corresponding optional parameters like 'bind-value:event', 'bind:format' etc.

After some digging it turned out that I was getting this for two reasons:

• Component names are now case-sensitive (I think that's related to #9860)
• I was missing a namespace

So, the compiler was quite right, my code was bad, but the error message had me pulling my hair out for a while.

Say I've made a declaration like this:
c# <MyButton OnClick="Clicked" @bind-Value="@MyTextProperty"/>
Is there any way the error checking could identify that there's a binding statement and then throw a warning/exception if the component name (MyButton) doesn't match up to a component the error-checker can find? I think this ties back to #9786 too.

[danroth27]

@tomRedox If you mistype the component name (ex you forget to add an @using for the component namespace, or you misspelled the name) as long as you typed the name using Pascal casing the compiler will assume the element is meant to be a component and you should get a warning if the component name doesn't resolve. Are you saying that wasn't the case?

[tomRedox]

@danroth27 it looks like it could be the order the warnings are generated in. Where there's a binding I think the compiler is diagnosing a binding issue before it does the component name check, so is reporting the binding error instead of the component error:

When I mistype the name of this component (should be TelerikDropDownList)

The red squigglies are then on the binding rather than the whole component declaration, and I get the misleading error:

The attribute names could not be inferred from bind attribute 'bind-Value'. Bind attributes should be of the form 'bind' or 'bind-value' along with their corresponding optional parameters like 'bind-value:event', 'bind:format' etc.

If I then delete the binding, the squigglies now highlight the whole component:

and the error changes to

Found markup element with unexpected name 'TelerikdropDownList'. If this is intended to be a component, add a @using directive for its namespace.

Trying this experiment with a couple of other components seems to show the same pattern:

This gives the bind error:

This gives the unexpected name error:

[mkArtakMSFT]

Closing as we think this is not impacting the community. If there are more similar reports, we will reconsider.

[tomRedox]

@mkArtakMSFT sure thing. I put a question and answer on this on stack overflow about this which has only garnered 760 views and 3 upvotes, so it looks like people are working this out for themselves

[mkArtakMSFT]

Thanks for sharing some insights, @tomRedox.
Question views are not proven source of it being something users were hitting, Upvotes, in contrast, are - but, as you said, there are so far just 3 upvotes for the 6 months period. We'll wait more.

[soomon]

@mkArtakMSFT please fix this issue. I have spent the hours trying to figure out why by 2 way binding suddenly stopped working and what is supposedly wrong with it until I found the SO thread and learned that the error might be completely misleading.
yes it was my fault not remembering I moved the component files, but showing an error that leads people into the wrong direction causes to much frustration. please fix it.
thanks!

[mkArtakMSFT]

Reopening and moving to the backlog to collect some more feedback.

[tomRedox]

This has got a bit more traffic on Stack Overflow now, up to ~2.6k views and 21 upvotes across the Q&A. Looks like more people are getting tripped up by this as Blazor adoption increases.