Use programatically check instead of assertion in method ComputeVisibleColumns of DataGridView.Methods to avoid null reference exception

[LeafShi1]

Fixes #13728

Root Cause

Due to this commit 9cbce69 (line 4827), the exception thrown on .net10.0 is System.InvalidOperationException, and the exception thrown on .net8.0 is NullReferenceException.

The original code does not make a null judgment but adds an assertion without verifying whether GetPreviousColumn(...) returned a valid column. In cases where:

• no previous column satisfies Visible & !Frozen,

dataGridViewColumn would be null, triggering an exception and terminating rendering.

Proposed changes

• Use logical judgment instead of assertion in method ComputeVisibleColumns of DataGridView.Methods to avoid null reference exception

Customer Impact

• When the leftmost column is hidden and the DataGridView is displaying only the last column, the rightmost column can also be successfully hidden.

Regression?

• No

Risk

• Minimal

Screenshots

Before

Setting DataGridViewColumn.Visible may throw NullReferenceException

BeforeChange.mp4

After

The rightmost visible column can also be successfully hidden.

AfterChange.mp4

Test methodology

• Manually

Test environment(s)

• .net 10.0.0-preview.7.25368.105

Microsoft Reviewers: Open in CodeFlow

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Codecov Report

❌ Patch coverage is 0% with 11 lines in your changes missing coverage. Please review.
✅ Project coverage is 76.90525%. Comparing base (91ebb74) to head (2bd21b6).
⚠️ Report is 38 commits behind head on main.

Additional details and impacted files

@@                 Coverage Diff                 @@
##                main      #13739         +/-   ##
===================================================
- Coverage   76.90565%   76.90525%   -0.00040%     
===================================================
  Files           3260        3260                 
  Lines         643088      643090          +2     
  Branches       47601       47602          +1     
===================================================
- Hits          494571      494570          -1     
- Misses        144848      144853          +5     
+ Partials        3669        3667          -2     

Flag	Coverage Δ
Debug	76.90525% <0.00000%> (-0.00040%)	⬇️
integration	18.98777% <0.00000%> (-0.01023%)	⬇️
production	51.57212% <0.00000%> (-0.00072%)	⬇️
test	97.42152% <ø> (ø)
unit	48.96373% <0.00000%> (+0.00869%)	⬆️

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Pull Request Overview

This PR fixes a potential null reference exception in the ComputeVisibleColumns method of DataGridView by replacing an assertion with proper null checking logic. The issue occurs when GetPreviousColumn returns null because no previous column satisfies the Visible & !Frozen criteria, which would cause the code to fail when trying to access properties of the null column.

• Replaces ThrowInvalidOperationExceptionIfNull assertion with conditional null checking
• Adds proper logic to handle cases where no valid previous column exists
• Maintains the same functionality while preventing crashes in edge cases

[ricardobossan]

All LGTM