Refactor ForceNewConnection

[mdaigle]

This PR is a refactor in service of #AB44829

Idle connection resiliency is a feature that replaces broken connections in-line before running a command. It utilizes a "replace" flow that follows the normal "open" flow but with a ForceNewConnection property set on SqlConnection. At certain critical points, we branch on this property to "create new" or "replace". These are really the same thing, but are exposed in a mutually exclusive way on the DbConnectionInternal subtypes. There's always one that works and the other throws NotImplementedException or InvalidOperationException.

It's very hard to understand where the property is set and when it might change. This PR removes the property and passes the desired behavior as a boolean argument.

[Copilot]

Pull request overview

This PR refactors the internal “replace connection” flow by removing the mutable SqlConnection.ForceNewConnection flag and instead threading an explicit forceNewConnection boolean through the open/replace pipeline (from SqlConnection → DbConnectionInternal → SqlConnectionFactory). It also removes the unused PrepareForReplaceConnection() hook from DbConnectionInternal.

Changes:

• Remove SqlConnection.ForceNewConnection and propagate a forceNewConnection parameter through open/reconnect code paths.
• Update connection factory + provider-base open logic to use the explicit forceNewConnection parameter when selecting ReplaceConnection vs pooled TryGetConnection.
• Remove DbConnectionInternal.PrepareForReplaceConnection() and corresponding call sites.

Reviewed changes

Copilot reviewed 7 out of 7 changed files in this pull request and generated 4 comments.

Show a summary per file

File	Description
src/Microsoft.Data.SqlClient/tests/UnitTests/Microsoft/Data/SqlClient/SqlConnectionStateTransitionTests.cs	Updates unit tests to call TryOpenInner(..., forceNewConnection) directly.
src/Microsoft.Data.SqlClient/src/Microsoft/Data/SqlClient/SqlConnectionFactory.cs	Adds forceNewConnection parameter and uses it to choose replace-vs-get logic.
src/Microsoft.Data.SqlClient/src/Microsoft/Data/SqlClient/SqlConnection.cs	Removes ForceNewConnection; uses explicit forceNewConnection in open/reconnect paths and in async retry state.
src/Microsoft.Data.SqlClient/src/Microsoft/Data/SqlClient/ConnectionPool/WaitHandleDbConnectionPool.cs	Removes call to the deleted PrepareForReplaceConnection() hook.
src/Microsoft.Data.SqlClient/src/Microsoft/Data/SqlClient/Connection/SqlConnectionInternal.cs	Ensures replace-connection path calls TryOpenConnectionInternal(..., forceNewConnection: true, ...).
src/Microsoft.Data.SqlClient/src/Microsoft/Data/ProviderBase/DbConnectionInternal.cs	Adds forceNewConnection argument to the internal open pipeline and passes it into the factory.
src/Microsoft.Data.SqlClient/src/Microsoft/Data/ProviderBase/DbConnectionClosed.cs	Threads forceNewConnection: false for initial open from the closed state.

[Copilot]

Pull request overview

Copilot reviewed 8 out of 8 changed files in this pull request and generated 3 comments.

[benrr101]

Love it! One request to improve readability, buuuuuuuuuuuuuuut I won't throw a fit over it.

[priyankatiwari08]

LGTM

[codecov]

Codecov Report

❌ Patch coverage is 89.65517% with 3 lines in your changes missing coverage. Please review.
✅ Project coverage is 64.01%. Comparing base (44e1b72) to head (58b03e6).
⚠️ Report is 18 commits behind head on main.

Files with missing lines	Patch %	Lines
...ient/src/Microsoft/Data/SqlClient/SqlConnection.cs	84.21%	3 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #4415      +/-   ##
==========================================
- Coverage   65.32%   64.01%   -1.32%     
==========================================
  Files         285      282       -3     
  Lines       43373    66572   +23199     
==========================================
+ Hits        28335    42616   +14281     
- Misses      15038    23956    +8918     

Flag	Coverage Δ
CI-SqlClient	?
PR-SqlClient-Project	64.01% <89.65%> (?)

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