Add a null-check for "DataGridView" property before executing OnMouseUp in function OnMouseUpInternal

[LeafShi1]

Fixes #12692

Root Cause

• This issue caused by PR Enable nullability in remaining DataGridViewCell members #10406，which removes the check whether the control is null before executing OnMouseUp in file DataGridViewCell.cs

Proposed changes

• Add a check if DataGridView is not null before executing OnMouseUp in function OnMouseUpInternal, because the Parent DataGridView might have been disconnected in the user event handler that is executed before this call, for example if the user clears the DataGridView row.

Customer Impact

• Application crashes when the customer clicks on a DataGridView cell, where previously the content was selected.

Regression?

• Yes, from NET8

Risk

• Minimal

Screenshots

Before

Object reference not set to an instance of an object exception pops up after clicked the DataGridViewCell content when the function DataGridView1_CellContentClick contains content
DataGridView1.Rows.Clear();
DataGridView1.Rows.Add(1, 0, "ABCD");

After

DataGridView Rows can be cleaned and re-added normally

Test methodology

• Manually, added a unit test

Test environment(s)

• .net 10.0.0-alpha.1.24631.2

Microsoft Reviewers: Open in CodeFlow

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 76.03495%. Comparing base (9007f33) to head (5e2c2a7).
Report is 5 commits behind head on main.

Additional details and impacted files

@@                 Coverage Diff                 @@
##                main      #12701         +/-   ##
===================================================
+ Coverage   76.00638%   76.03495%   +0.02857%     
===================================================
  Files           3181        3181                 
  Lines         639670      639690         +20     
  Branches       47215       47215                 
===================================================
+ Hits          486190      486388        +198     
+ Misses        149968      149775        -193     
- Partials        3512        3527         +15     

Flag	Coverage Δ
Debug	76.03495% <100.00000%> (+0.02857%)	⬆️
integration	18.16641% <0.00000%> (+0.12049%)	⬆️
production	49.82444% <100.00000%> (+0.05940%)	⬆️
test	97.03157% <100.00000%> (+0.00270%)	⬆️
unit	47.05064% <100.00000%> (-0.00035%)	⬇️

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[ricardobossan]

I tested the PR code, and the issue appears to be resolved:

LGTM!

[Tanya-Solyanik]

Thank you for jumping on this issue! Looks good, I added only minor comments.
Could you please also review the rootcause PR for similar cases, for example other instances of invocations of user-provided event handlers that are followed by an access to the parent DGV?

[Tanya-Solyanik]

This change looks confusing because at the top of this method we tested that DGV is not null already. Please add a comment explaining that the custom Click event handler might delete the cell and the parent DGV.

[Tanya-Solyanik]

Consider:

Suggested change

	SubDataGridViewCheckBoxCell cell = (SubDataGridViewCheckBoxCell)dataGridView.Rows[0].Cells[0];
	var cell = (SubDataGridViewCheckBoxCell)dataGridView.Rows[0].Cells[0];

[Tanya-Solyanik]

Could you please inline this event handler to make the test more case self-contained.

dataGridView.CellContentClick += new DataGridViewCellEventHandler((s, e) =>
{
DataGridView dataGridView = (DataGridView)s;
dataGridView.Rows.Clear();
dataGridView.Rows.Add();
}
);