[Parameter] is necessary also for [SupplyParameterFromQuery]

[JZO001]

Description

In the section "Query strings", information is missing. "SupplyParameterFromQuery" does not stand alone, [Parameter] attribute is also necessary. Without it, the parameter from the query will not be processed.

Page URL

https://learn.microsoft.com/en-us/aspnet/core/blazor/fundamentals/routing?view=aspnetcore-8.0

Content source URL

https://github.com/dotnet/AspNetCore.Docs/blob/main/aspnetcore/blazor/fundamentals/routing.md

Document ID

b6cb2574-6326-a40d-0b6c-d1661328e828

Article author

@guardrex

[github-actions]

🎉🥳 Happy New Year! 💃🕺

A green dinosaur 🦖 will be along shortly to assist. Stand-by ........

[guardrex]

Not strictly necessary AFAIK. Let's ping @MackinnonBuck ... Should the guidance add a line that says something like ...

If the query string parameter must also serve as a [component parameter](xref:blazor/components/index#component-parameters), also include the [`[Parameter]` attribute](xref:Microsoft.AspNetCore.Components.ParameterAttribute):

... and then I can add a little example like ...

[Parameter]
[SupplyParameterFromQuery]
public string? Filter { get; set; }

[JZO001]

On my side - using .NET 7.0.15 - on a normal page (not a component), I used the "SupplyParameterFromQuery" to get an int? parameter from query. It does not work, and I had to google for a while to figure out the reason. Than I spotted out, in other examples, there is the "Parameter" also. After added it to my property into my page, than it started to work fine.

[guardrex]

normal page (not a component)

I don't understand. This API is only for Razor components AFAIK.

Mackinnon, one of our TOP product unit engineers will be along in a bit to take a look at this and advise further. I'll email him, too, to make sure he gets the ping. He usually responds by EOD unless he's OOF. Stand-by .......................

[MackinnonBuck]

On my side - using .NET 7.0.15

Ah, yep. Before .NET 8, both [Parameter] and [SupplyParameterFromQuery] were required in order for a parameter's value to be supplied via query. We removed this requirement in .NET 8.

AFAICT, the docs are correct - the .NET 8 page omits the [Parameter] attribute, and the .NET 7 page includes it.

@guardrex, do you think it would make sense to add a note in the .NET 8 version of the docs to clarify that when using a version earlier than .NET 8, the [Parameter] attribute must be used in conjunction with the [SupplyParameterFromQuery] attribute? Or do we try to avoid including info about previous .NET versions?

[guardrex]

add a note in the .NET 8 version of the docs ... Or do we try to avoid including info about previous .NET versions?

Yes ... that's right about not adding it to the reference doc. I'll place a section on this in the Migration article. We mostly avoid doing it in the reference docs because they would eventually be filled with thousands of little "this changed in version X" remarks.