As I understand it, you’d like DataGridView to behave in the manner we’re all accustomed to in MS Excel where you can see all of the lines of a multiline entry during editing, before commit and the row height adjustment that results.

What I reproduced from your code is that only the last line of a multiline entry is visible during editing, but appears normally after commit.

Here’s one way that worked for me in testing. Ordinarily, the underlying cell value isn’t changing when the text in the editing control does. The value is copied on a commit, and cancelling the operation simply skips the copy operation.

But by changing the underlying cell value in response to changes in the editor control, then the row height tracks because of the AutoSizeRows setting. If the edit is cancelled, however (e.g. the [Escape] key is pressed) it’s now our responsibility to revert the cell value using the _revertText value that was pushed when the editor was shown.

Preconditions:

• DefaultCellStyle.WrapMode is set to DataGridViewTriState.True
• AutoSizeRowsMode is set to DataGridViewAutoSizeRowsMode.AllCells
• [Shift][Enter] to add new line

public partial class MainForm : Form
{
    public MainForm() => InitializeComponent();
    protected override void OnLoad(EventArgs e)
    {
        base.OnLoad(e);
        dataGridView.DataSource = Records;
        dataGridView.AutoSizeColumnsMode = DataGridViewAutoSizeColumnsMode.Fill;
        dataGridView.DefaultCellStyle.WrapMode = DataGridViewTriState.True;
        dataGridView.AutoSizeRowsMode = DataGridViewAutoSizeRowsMode.AllCells;
        dataGridView.EditingControlShowing += (sender, e) =>
        {
            if (e.Control is TextBox textBox)
            {
                Debug.Assert(textBox.Multiline, "Already true, and this is due to WrapMode property setting");
                _revertText = textBox.Text;
                textBox.TextChanged -= localOnTextChanged;
                textBox.PreviewKeyDown -= localPreviewKeyDown;
                textBox.TextChanged += localOnTextChanged;
                textBox.PreviewKeyDown += localPreviewKeyDown;

                void localOnTextChanged(object? sender, EventArgs e)
                {
                    BeginInvoke(() => // Because drawing artifacts have been known to occur otherwise.
                    {
                        dataGridView.CurrentCell.Value = textBox.Text;
                    });
                }
                void localPreviewKeyDown(object? sender, PreviewKeyDownEventArgs e)
                {
                    if(e.KeyData == Keys.Escape)
                    {
                        dataGridView.CurrentCell.Value = _revertText;
                    }
                }
            }
        };
        dataGridView.CellValidating += (sender, e) =>
        {
            Debug.WriteLine(
                $"Ensure that, regardless, only one cell validation happens per commit {dataGridView.CurrentCell?.Value}");
        };
        Records.Add(new Record());
    }
    string _revertText = string.Empty;
    BindingList<Record> Records = new BindingList<Record>();
}
class Record
{
    public string? Description { get; set; }
}