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Clarification needed? #44404

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bstordrup opened this issue Jan 16, 2025 · 2 comments · May be fixed by #44408
Open

Clarification needed? #44404

bstordrup opened this issue Jan 16, 2025 · 2 comments · May be fixed by #44408
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@shethaadit
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dotnet-csharp/svc fundamentals/subsvc help wanted Good for community contributors to help [up-for-grabs] in-pr This issue will be closed (fixed) by an active pull request.

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@bstordrup
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bstordrup commented Jan 16, 2025 •
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Type of issue

Other (describe below)

Description

The section about Optional arguments could in my opinion be improved with a description of how nullable types fit in with respect to whether they are optional or not.

The section specifically says that an argument is considered optional if it has a default value assigned in the parameter list. But one could argue that because of the nullability, a T? myArgument definition does implicitly have a default value being null or default(T).

Looking into the C# Language Specification does not enlight the issue either.

Page URL

https://learn.microsoft.com/en-us/dotnet/csharp/programming-guide/classes-and-structs/named-and-optional-arguments#optional-arguments

Content source URL

https://github.com/dotnet/docs/blob/main/docs/csharp/programming-guide/classes-and-structs/named-and-optional-arguments.md

Document Version Independent Id

6be20f15-e5eb-0778-5fbe-38326d8e8f00

Article author

@BillWagner

Metadata

  • ID: e335f6e5-7d90-bfab-f95d-ab8ef3ba41fc
  • Service: dotnet-csharp
  • Sub-service: fundamentals

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@dotnet-policy-service dotnet-policy-service bot added the ⌚ Not Triaged Not triaged label Jan 16, 2025
@BillWagner BillWagner added help wanted Good for community contributors to help [up-for-grabs] and removed ⌚ Not Triaged Not triaged labels Jan 16, 2025
@BillWagner
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BillWagner commented Jan 16, 2025 •
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Hi @bstordrup

I can see the need for more clarification. Your question is using two different forms of "optional".

  • A parameter that's nullable (T?) is optional, meaning that the argument can be null: void M(T? paramThatCanBeOptional)
  • An optional parameter is one declared with a default value. Callers need not supply an argument: void M(T optionalParam = someConstantValue). Callers could use thing.M(), eliding the argument for the optional parameter.

Adding to the confusion, a parameter could be both forms of optional: void M(T? allTheOptionalMeanings=default)

We'll look at this to determine how we can make that more clear to readers I've also added the "help wanted" tag if anyone wants to submit a PR before we make our next update here.

@shethaadit
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Hi @BillWagner, I will raise PR for this soon. Could you please assign this to myself?

@shethaadit shethaadit linked a pull request Jan 16, 2025 that will close this issue
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@dotnet-policy-service dotnet-policy-service bot added the in-pr This issue will be closed (fixed) by an active pull request. label Jan 16, 2025
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Clarify Optional Parameters and Nullable Optional Parameter Behavior in C#. shethaadit/docs
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@BillWagner @shethaadit @bstordrup