Add DefaultInterpolatedStringHandler.Text/Clear

[stephentoub]

Fixes #110505

[dotnet-issue-labeler]

Note regarding the new-api-needs-documentation label:

This serves as a reminder for when your PR is modifying a ref *.cs file and adding/modifying public APIs, please make sure the API implementation in the src *.cs file is documented with triple slash comments, so the PR reviewers can sign off that change.

[dotnet-issue-labeler]

Note regarding the new-api-needs-documentation label:

This serves as a reminder for when your PR is modifying a ref *.cs file and adding/modifying public APIs, please make sure the API implementation in the src *.cs file is documented with triple slash comments, so the PR reviewers can sign off that change.

[TrayanZapryanov]

I am wondering if concerns about exposing ValueStringBuilder are not applicable here too. Soon I've copied ValueStingBuilder in our codebase and build a handler like DefaultInterpolatedStringHandler but storage was VSB. Then was asked by colleagues what will happen if they forgot about calling Clear(Dispose in our case).

[stephentoub]

Then was asked by colleagues what will happen if they forgot about calling Clear(Dispose in our case).

An ArrayPool array may not be returned to the pool.

[hamarb123]

Is there any particular reason why Text and ToString aren't marked readonly, btw?

[mgravell]

@hamarb123 valid question; they probably could/should be

[stephentoub]

Is there any particular reason why Text and ToString aren't marked readonly, btw?

@hamarb123 valid question; they probably could/should be

Lots of members could be. Why should these be? Passing around a DefaultInterpolatedStringHandler by in seems like a bad idea.

[mgravell]

You're right, upon consideration; adding readonly is only useful on a flavor of usage that actively does not apply to this type.