Issue 14204 fix data grid view excessive cpu+memory usage

[LeafShi1]

Fixes #14204

Root Cause

The foreach loop over DataGridViewRowCollection uses an enumerator that calls this[index], which unshares (clones) each shared row. For 700k rows, this causes massive memory allocation and CPU usage.

Proposed changes

• DataGridView.Methods.cs:
  • Added ReleaseRowUiaProviders() helper method
  • Modified ReleaseUiaProvider() to use HashSet deduplication instead of foreach
• DataGridViewColumnCollection.cs:
  • Modified RemoveAtInternal() to use HashSet deduplication

Customer Impact

• Applications with large DataGridView (700k+ rows) freeze for several seconds when closing forms or removing columns

Regression?

• Yes (The regression was introduced in this commit)

Risk

• Minimal

Screenshots

Before

Closing a form with 700k rows causes 5-10+ seconds of UI freeze and high memory spike due to row cloning.

After

Form closes near-instantly with minimal memory overhead.

Test methodology

• Manual test

Test environment(s)

• .net 11.0.0-alpha.1.26057.107

Microsoft Reviewers: Open in CodeFlow

[LeafShi1]

This fix has been tested and verified.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 97.40479%. Comparing base (15506ad) to head (2394af7).
⚠️ Report is 26 commits behind head on main.

Additional details and impacted files

@@                 Coverage Diff                  @@
##                main      #14224          +/-   ##
====================================================
+ Coverage   77.15242%   97.40479%   +20.25237%     
====================================================
  Files           3279        1214        -2065     
  Lines         645333      357428      -287905     
  Branches       47720        5598       -42122     
====================================================
- Hits          497890      348152      -149738     
+ Misses        143757        8484      -135273     
+ Partials        3686         792        -2894     

Flag	Coverage Δ
Debug	97.40479% <ø> (+20.25236%)	⬆️
integration	?
production	?
test	97.40479% <ø> (-0.00080%)	⬇️
unit	?

Flags with carried forward coverage won't be shown. Click here to find out more.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.

[Copilot]

Pull request overview

This PR fixes a critical performance issue in DataGridView where applications with large datasets (700k+ rows) experience severe UI freezes when closing forms or removing columns. The root cause was that iterating over the DataGridViewRowCollection using foreach would unshare (clone) each shared row, causing massive memory allocation and CPU usage.

Changes:

• Replaced inefficient foreach loops that trigger row cloning with HashSet-based deduplication using direct SharedList access
• Added a helper method ReleaseRowUiaProviders() to centralize row UIA provider cleanup logic
• Applied the same optimization pattern to both form disposal and column removal scenarios

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 3 comments.

File	Description
DataGridView.Methods.cs	Added ReleaseRowUiaProviders() helper and modified ReleaseUiaProvider() to use HashSet deduplication when iterating over rows, preventing costly row cloning
DataGridViewColumnCollection.cs	Modified RemoveAtInternal() to use HashSet deduplication when releasing UIA providers for cells in the removed column

Please fix the failure test cases firstly.