DataGridView vertical scrollbar not updating properly (Forms bug?)

I've just had this problem (my form was disabled while adding rows) and solved it by setting the scrollbar property of the grid to 'None' before adding the rows then setting it back to 'Both' once all my rows have been added.

This also solved the problem for me:

DataGridView.SuspendLayout();
DataGridView.ResumeLayout();

It can be called before the DGV is re-enabled.

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UPDATE: This also does the job:

DataGridView.PerformLayout();

My problem was that my vertical scrollbar disappeared completely. I flailed with all of the above suggestions and finally discovered that making the panel containing the DataGridView narrower than the form solved the problem. In my case, 16 pixels narrower worked.