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Missing discussion of allowed expressions for attribute constructor arguments #6428

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binki opened this issue Jul 12, 2018 — with docs.microsoft.com · 5 comments
Open

Missing discussion of allowed expressions for attribute constructor arguments #6428

binki opened this issue Jul 12, 2018 — with docs.microsoft.com · 5 comments
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doc-enhancement Improve the current content [org][type][category] dotnet/svc Pri1 High priority, do before Pri2 and Pri3

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@binki docs.microsoft.com
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binki commented Jul 12, 2018 •
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I’m not sure exactly where this belongs. Perhaps it belongs in the Applying Attributes article instead. But it could also make sense here because the allowed constructor expressions limits the types of parameters one can meaningfully accept in an attribute’s constructor.

The expressions allowed as parameters to attributes are very limited. I think it includes constant expressions (notably including the useful nameof()) plus a at least one one exception typeof(TypeName) (if not other special expressions). It might also be worth discussing how CallerInformationAttribute can be applied to an attribute constructor’s parameters to get the name of the member the attribute is being applied to.

I expected this to be documented, but I can’t find the documentation for it. I looked in these places:

  1. Applying Attributes
  2. Writing Custom Attributes
  3. Retrieving Information Stored in Attributes
  4. “Attribute Parameters” in Attributes

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@phillijw docs.microsoft.com
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phillijw commented Sep 9, 2019

It would also be nice to see some discussion of how I deal with dependency injection for these constructors. Perhaps it's not allowed at all?

@binki
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binki commented Sep 9, 2019

@phillijw For these constructors, you mostly can do DI indirectly through passing in Types and making whatever is processing the attributes aware of your DI. For example, some DI systems themselves let you mark objects with attributes specifying arbitrary values such as names or priority levels so that your runtime code can select between alternative implementations. But attributes themselves are restricted to constants and Type. I do not think that discussion relates to the issue I filed and it might be beyond the scope of the documentation on attributes itself. Please consider opening another one if you want to explore that.

Thanks!

@tdykstra tdykstra added doc-enhancement Improve the current content [org][type][category] P1 labels Nov 18, 2019
@PRMerger8 PRMerger8 added the Pri2 label Jan 16, 2021
@dotnet-bot dotnet-bot added the won't fix Issues that were closed as part of automated backlog grooming label Jan 25, 2021
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This issue has been closed as part of the issue backlog grooming process outlined in #22351.

That automated process may have closed some issues that should be addressed. If you think this is one of them, reopen it with a comment explaining why. Tag the @dotnet/docs team for visibility.

@binki
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binki commented Jan 25, 2021

@BillWagner This is still an issue.

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binki commented Jan 25, 2021

@dotnet/docs @akoeplinger ^

@sharwell sharwell removed the won't fix Issues that were closed as part of automated backlog grooming label Jan 25, 2021
@sharwell sharwell reopened this Jan 25, 2021
@gewarren gewarren added Pri1 High priority, do before Pri2 and Pri3 and removed P1 Pri2 labels Jan 29, 2021
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