DataGridView cannot be Focused, but one of them can

I've come across the strangest bug pertaining to DataGridViews in Windows Forms.

I have a TabControl, that is supposed to contain a docked DataGridView in each tab page. I thought it would be convenient that the grid is focused upon changing the tab page, so that the user could simply hover the mouse over the grid and start scrolling when he changes the page. So, I just put a grids[tabs.SelectedIndex].Focus() in the event开发者_JAVA百科 handler for changing the tab page.

However, something really strange happened. In my test application, I have three tab pages. If I try scrolling the grid right after starting the application, it doesn't work; I have to click in the grid first. I was expecting this. However, if I change the tab page, I can't scroll in any of the other grids until I click, except for the first one!

So, if I switch pages to the second page, then back to the first, I can automatically scroll that grid without clicking, but if I then switch to the third, I have to click for the grid to focus.

I had a look at the CanFocus properties of the grids, and it seems that only the first grid has it set to True. They are all created programmatically, and all in the same way. I don't see why they would be different.

Any ideas?

Inactive tab pages have their Visible property set to false. The documentation for CanFocus says:

In order for a control to receive input focus, the control must have a handle assigned to it, and the Visible and Enabled properties must both be set to true for both the control and all its parent controls

Well, I solved it. Stupid programming error on my part, I had grids[tabs.TabIndex].Focus() instead of grids[tabs.SelectedIndex].Focus().

Oh well.