TreeDataGridCell sends a wrong index in RaiseCellPrepared about avalonia.controls.treedatagrid HOT 6 CLOSED

This problem is related not to the master branch but to #8

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@danipen @miryamGSM Would it be possible for you guys to provide more info about this issue or some repro?
From my POV it's impossible for OnAttachingToLogicalTree to be called without creating of cell. So if cell is created this code makes sense and no additional validations are needed.

from avalonia.controls.treedatagrid.

Hi @Takoooooo, unfortunately I don't have a minimal example to reproduce this issue, and I'm afraid that it's not easy to build, since I'm not sure why/when it happens (it happens "sometimes" when switching from views, and re-creating the TreeDataGrid).

As you can see in the image, there are a unwanted state:

• The method OnAttachedToLogicalTree is raising the event RaiseCellPrepared for row 0.
• However, the TreeDataGrid has no rows at this moment (the _treeDataGrid.Rows collection is empty).

Is feasible to protect this scenario? Does it make sense for you?

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@danipen The problem is what protecting it doesn't really have a sense. OnAttachingToLogicalTree should not be called because we don't create any rows and the Rows collection is empty. I tried to make a test which would repro this but unsuccessfully. And also we cant just blindly protect that because it doesn't have a sense. I can only suggest you to make the repro or to protect from that locally in your code

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There's a repo of this on the repro-cases/wrong-index-raise-cell-prepared branch.

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Taken a look at the repro and the problem seems to be that:

• TreeDataGridExpanderCell contains an "inner" cell that is used to display the cell data
• When TreeDataGridExpanderCell gets realized, it calls UpdateContent to realize the inner cell, setting RowIndex/ColumnIndex
• When TreeDataGridExpanderCell gets unrealized, UpdateContent gets called again, but it doesn't unrealize the inner cell because _model is already set to null here

I think we just need to remove that _model is null check in TreeDataGridExpanderCell.UpdateContent. think that when model is null we need to call Unrealize() on the inner cell.

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